Tri-z PowerValve

[NeverLift]

Here is my current project.

85 tri-z cases
86 tri-z transmission
85 YZ250 crank shaft Hot Rods connecting rod & bearings
85 YZ250 Cylinder (ported & polished cylinder)
Sprock Head
Wiseco YZ250 piston 68.5mm
38mm Keihin PWK
Boyesen Power Reeds
LRD Pipe
Unknown silencer
Complete chassis All Balls bearings
2001 CR125 Forks
Works quadcross rear shock
Lonestar +2 axel
Metal Tech +3 Swingarm Banshee round carrier
Hall Performance Triple Tree's
2001 CR125 Forks
2001 CR125 Froks -6"
Billet Thermostat Eliminator
Unhinged ATV Foot Pegs
250R Front Hub
10" 250R Wheel
Hoosiers on All 3
Adjustable Rear Lowering Link
Top Mount Tank
Still need to mount the radiators, gas tank, foot pegs, rear brakes, chain and sprocket. Then I will be breaking it in and jetting it. I planed on polishing the whole motor but ran out of time. I am going to Badlands Off Road Park on the 13th-17th of this month.
This is as far as I got before I had to go out of town on business. I'll be back this weekend to finish.

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[3 Wheel Drive]

Looking good, I like your air box set up! How are the power valve yz cylinders vs the Tri Z's?

[NeverLift]

I have never ridden this year YZ. Cylinder stud holes line up perfect, exhaust is the same angle and diameter, head is the same, the reeds/reed cage is much larger, the intake comes out at an angle so I had ordered some turbo intercooled piping so the intake doesn't touch the exhaust(but it's very close). The flywheel is also way smaller.

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[Rigaman]

How are you gonna fit the seat?

[NeverLift]

I had to cut the plastic and remove a little foam from the bottom of the seat for the intake pipe to fit but I have a tall desert seat so it works just fine. Here is a picture with the seat and airbox cover on.

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[NeverLift]

Got some time today to throw a wrench at her. Everything is together except for the fenders. I started it for the first time and heat cycled it 5 times. Took it for a short ride on the 3rd heat cycle I barley got on it not even 1/2 half throttle and she feels pretty snappy. Can't wait till tomorrow to ride it a bit I've only got about a 600 yard straight away at the house to ride on but that should be good for the first few 10 minute rides. If I have enough light after that I will put in a fresh plug and do a plug chop to get the jetting dialed in.

Here is a short clip of it running in the garage.

http://www.youtube.com/watch?v=EwtqC_6yLqQ

[C.J]

Holy sheet thats awesome!!!! I wonder if Klemm can 350 the YZ cylinder.... hehe ,,,, I Seriously dig it man!!!

[NeverLift]

I ordered a Dial-a-Jet from Thunder Products today. I've never used one but always wanted to try it so I pulled the trigger. I will be installing on Friday and will report my findings. I have ridden my trike a few 10 minute rides taking it easy seems to run good( I only have about 20 minutes of sunlight after work to ride it). This weekend I will hammer on it after I install the dial-a-jet. Sunday-Wednesday I will be going down to Badlands offroad park in Attica, IN come on out if you can make it.

[Rigaman]

I had to cut the plastic and remove a little foam from the bottom of the seat for the intake pipe to fit but I have a tall desert seat so it works just fine. Here is a picture with the seat and airbox cover on.

178282

Thats really cool man! I like everything you have done. I am very curious to hear how it rides. I have heard mixed things about these powervalve cylinders on tri-z's. This is something I have wanted to do since my first tri-z.

[C.J]

What pipe are you running on this beasty? I wonder how my Phase-5 would do with the powervalved cylinder. Or if it's be best to get a custom pipe made

[NeverLift]

I'm running an LRD pipe. I don't know if this is the best option but I love this pipe.

[NeverLift]

I have the Z running but not good it breaks in high RPM no matter what jetting I throw at it. I am rebuilding the fuel pump with OEM parts. I also thought that the issue maybe caused by the nipple that goes into the cylinder. When I ported the transfers I ground the end protruding into the transfer port flush with the inner cylinder wall. Do you think this could have an ill effect? I will replace it anyway I have plenty of junk cylinders I can borrow from. I might shelf this project till the snow melts I don't like trailering with all the salt on the roads.

Did a little walk around video of the Z (and the 400ex)yesterday. I know it's boring but I thought I'd share.
https://www.youtube.com/watch?v=kIDz3h-vYpU&feature=youtu.be

[NeverLift]

Fuel pump is rebuilt and still lean. I have a 220 main in it now it is much better but the plug chop is a very light tan color. I just bought 222 up to 238 and that's the biggest I can find. Hopefully one of them does the trick. With the tri-z motor same carb I had a 178 main I never thought I would have to go up this much but it keeps pulling harder the bigger I go. Leaving for Little Sahara in just over a week!!!!!!!!!!!!!!!

[C.J]

Wow! Keep us updated for when you get the jetting dialed in.

How's your float level? Have you tried changing the needle out?

Get us another video when she's all squared away!!!!!

[El Camexican]

That just doesn’t seem right. I would suggest you check the float height as per above (could be low) and also the reeds. If your fuel pump is working properly and you have no air leaks I can’t imagine you should need that massive jet.

PS. Trike looks great!!!

[Rider414]

I remember a thread on here that a member had a Tri Z that could not get the top end to run clean, I believe it ended up being the rectifier.

[NeverLift]

Might be that huge intake and this is the first polished exhaust port I've done. Also added the boost port like on all my previous Tri-z cylinders. It gets faster and faster the bigger I go with the main jet. I don't think anything is wrong. I'm just amazed it's this thirsty. I've seen 500's with this same carb running a smaller main. I will be doing some more testing tomorrow after work.

Float level is ever with the float bowl mating surface.

New Boysen power reed Reeds.

No air leaks did the old starting fluid around the intake/gaskets trick. Idle didn't fluctuate at all.

YZ wire harness/engine so no rectifier or regulator.

I will have tons of video after Rampage.

[Stephon_xr500]

I'm extremely interested in how your motor turns out. I just picked up an 86 tri-z I'm throwing a carb from a 82 yz250. I have the 82 yz motor as well but this 86 tri-z motor feels like it's going to run just fine. Could you post some pics of your motor and carb please

Good luck

[YTZ drew]

I've seen 500's with this same carb running a smaller main.

Keep in mind a bigger engine will pull a greater vacuum than a smaller one if they have the same size carb. Bigger carbs on smaller engines= larger jets than it came with initially.

[C.J]

Hey Neverlift, would you mind me sharing pictures of your bike on the Three Wheeler Appreciation Team Facebook page?

[NeverLift]

Hey Neverlift, would you mind me sharing pictures of your bike on the Three Wheeler Appreciation Team Facebook page?

Go for it! Send me a link after. I've been thinking about joining FB just for the trike network.

[NeverLift]

Well,

After playing with the jetting last night I've come to the conclusion that's not it. It runs best with a 205 main jet anything bigger and performance drops and flattens out at high rpm any leaner and it wont pull as high into the rpm. But the plug is a very very light tan regardless of the main.

Also put my timing light on to see if spark was breaking up at high rpm and it was flashing as solid as ever.

So I bought a Factory service manual today and found some useful info about adjusting the exhaust valve. There is a hole in the linkage arm and a machined hole in the cylinder that you put a dowel in to align everything then tighten down the 2 nuts. I did not do this. I will also set my ignition timing as per the manuals specs. Hopefully this will do the trick.

[elvetost]

Any updates on this please? :D

[NeverLift]

Holy Crap it's been way too long and the sad thing is i'm on this site 5 times a day. A lot has changed.

Sprock Head YZ cut dome for pump gas but it still has 220psi. I have a race gas cut dome but never installed it, the compression would be thru the roof.I did the old Soldier on top of the piston trick but can't rember the measurement now. What clearence should i have? Pump and 110.
2001 cr125 forks
+3 Metal Tech Swingarm
Banshee rear end components
G-force rear hubs
Maybe more I can't remember.

Now it still flattens out on top. I'm leaning towards my Intake,porting and pipe combo not jiving with each other. For a all the experts out there. What would be the difference between a pipe on at standard cylinder vs a powervalve cylinder? I have done a leakdown and it held 7psi for 24 hours. I am open to any and all suggestions.

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[El Camexican]

She's real purrrrdy! :beer I'm no expert, but three questions...

Are you certain that the power valve is opening all the way?
Have you played with your timing at all?
You seem to have a fair bit of plumbing going on to the air filter, have you tried running it with a simple pod filter to see if that makes a difference?
Those would be the first three places I looked for top end.
If it is an issue with the pipe you may be able to get it to rev a bit higher by shortening the head pipe a bit, but I wouldn't want to cut that pipe you have up to test the theory.

[NeverLift]

El,
I have taken the PV cover off and rev it slowly and it opens all the way. I have also adjusted from factory to be slightly lower and higher neither one cleared up my issue. I will ride it with the cover off and feel for it opening under load this weekend.

I set the timing with my dial indicator to factory spec. My last test session I restarted the timing a hair (no difference and the cover was covered in mud so i quit for the day) but the stator plate has a lot of adjustment so i'll keep going little by little till I'm full retard and see how that goes.

Yes that intake is long and big diameter. I have thought that it is just to much. I've got a K&N pod that I'll try to mount this weekend.

Yeah I'm not cutting up this exhaust. Its an LED (LRD from the day) I want to call Arlen and ask him how he would build it different for my application. However I want to have the funds available for a custom pipe before I call and blow smoke. I was thinking about putting the stock pipe on and seeing how it likes that.

I know to do these things one at a time. Thanks for the suggestions. Gives me some more stuff to test.

[roll on 3]

Did you drill out or change the fuel tee. That helped jetting for me.

[NeverLift]

I didn't drill out the tee but last time I was testing I used a raptor tank in my lap to bypass all the fuel circuit to rule that out.

[onformula1]

Wow, that is a nice Tri-Z. Nice swing arm, Tyler makes some great products.

I would try dropping the compression 220 is very high and will take away upper mid, top end and over rev. Look at a modern YZ250 the PSI is 156 and that was reduced recently from 160 and the engine is faster. I would stay around 180 or less. I think you would like that motor with a stock head. Those reeds will start to fludder on the top end a pair of carbon Tech hi tension reed would be great in there. If you start at the stock timing and then retard at 1mm increments you will find the sweet spot where you will be happy, too much of a good thing can be a bad thing. :lol: It sounds like you are following the correct power valve adjustment, there maybe new found power in the jetting. I would also test the stock air box with no lid a air box can give you more velocity and will often out perform a POD. Check the fuel delivery the Tri-Z has been known for a few issues a top mounted tank can work wonders too. Try testing a spark plug one heat range colder as well, you may be surprised.

[nstyle73]

Just a question, as I have some experience with the Spock heads and the momentous compression, could you have a touch of detonation causing it to break up? I didn't see whether you were running the Sprock head the entire time or not. I have a Spock head on my Tecate, with around 215psi, and running 50/50 110 made my life a lot simpler.

[cr480r]

Years back I had a Suzuki LT250 that had similar symptoms. RM cylinder, RM single ring piston and light pin, head cut 215psi, 'early style reed cage(big) w/ medium carbon techs, PT rev pipe, 39 PWK, clamp-on, lightened flywheel..... Bike started and ran flawless at part throttle, but once on main circuit it ran flat and sounded like lean bog. Tried jets from 150-200 with little change.. I messed with floats, petcock mods, vent etc.. No change. I finally swapped the complete ignition system from a friends bike.. Instantly had a rich condition.. Started dropping jets till it cleaned up.. 168-170 I think.. Bike was now fast, had fantastic mid-top power that didn't end.... until it broke a rod a few rides later.. It had been losing spark when it came on the pipe, and it got worse as I added more powerful components .. Caused me fits. I isolated the ignition problem down to the stator, even though it still tested OK by the book. Every since then I always suspect ignition trouble when a bike is unresponsive to jet changes.. High compression will show you a weak ignition everytime. .018 plug gap can help. I know lower compression can give gains up top, but high compression bikes will rev just fine when everything is right.. And pull better "off pipe"

[NeverLift]

onformula1,
Tyler did a fantastic job great guy to deal with. I love the swingarm. For the head i wanted it to be pump gas 180 PSI but that didn't happen. I would like to have it turned in a lathe to lower the compression. What should the clearance be between the head and piston to bring me back to the 180psi range? I did run with the stock head and still had this problem. The only difference i noticed with the Sprock head is that it pulls much harder down low now. Carbon tech reeds are on the shopping list i knew before i posted that you were going to recommend them. Now with this Intake setup i'll have to get a top mount from John.
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Last night I eliminated the long intake tube and came up with this. Hopefully it works better, it was well after dark when i finished. I tried to make the airbox work but with the different carb angle it's a no go at least with what i had on hand. Next time out i will adjust my timing in 1mm increments as you suggested.

nstyle73,
I am running 110 in her so i don't believe it's detonating. I have ran the stock head and sprock head with the same issue. I think i bought these triples from you.

cr480r,
Sounds like You had my exact problem. I am going to test these other suggestions this weekend. If nothing comes of it i will source some "new" used ignition components. Everything i have is within spec of my factory service manual.

Thanks for all the advise guys, I've got some work ahead of me this weekend. Hopefully the wife doesn't bombard me with honey do's.

[yaegerb]

onformula1,
For the head i wanted it to be pump gas 180 PSI but that didn't happen. I would like to have it turned in a lathe to lower the compression. What should the clearance be between the head and piston to bring me back to the 180psi range?

Need to figure out with the volume of your current head is. My guess is its 18CC or below...possibly even 15. I agree with Milner, those are some high numbers you are playing with. I see you are using 110....dunno if that's high enough for the comp's you are running. You need to perform a UCCR to gauge your octane rating. I can tell you my 250R was running like crap about 2 years ago and I performed the UCCR and found my uncorrected compression ratio to be 16:1 and should have been using 116 or higher octane...food for thought. My comp at the time was 218. My head ended up being 15cc's. That was a time bomb waiting to go off. BKM gave me an 89 TRX head to try and solved all my problems. The 89TRX head was stock at 23cc's.

To drop that comp back down you need to get the bowl re chambered, I am only guessing here, but 23-25 CC's should be sufficient.

[El Camexican]

Perhaps its as simple as adding a second base gasket? Raise the ports and lower the compression all at once, should equate to more top end RPM, no?

[yaegerb]

Perhaps its as simple as adding a second base gasket? Raise the ports and lower the compression all at once, should equate to more top end RPM, no?

That will definitely help...that's an oldschool fix. It will come on the pipe in the upper RPM's since you are raising the ports though. I like my power low-mid. All depends on preference.

[NeverLift]

Need to figure out with the volume of your current head is. My guess is its 18CC or below...possibly even 15. I agree with Milner, those are some high numbers you are playing with. I see you are using 110....dunno if that's high enough for the comp's you are running. You need to perform a UCCR to gauge your octane rating. I can tell you my 250R was running like crap about 2 years ago and I performed the UCCR and found my uncorrected compression ratio to be 16:1 and should have been using 116 or higher octane...food for thought. My comp at the time was 218. My head ended up being 15cc's. That was a time bomb waiting to go off. BKM gave me an 89 TRX head to try and solved all my problems. The 89TRX head was stock at 23cc's.

To drop that comp back down you need to get the bowl re chambered, I am only guessing here, but 23-25 CC's should be sufficient.

My dome was engraved with the CC on it but i can't remember what it says. i'll pull it off and take a look.

[NeverLift]

Perhaps its as simple as adding a second base gasket? Raise the ports and lower the compression all at once, should equate to more top end RPM, no?

I seem to remember that someone sent you a thick base gasket for your engine build. If you didn't use it maybe you'd be willing to part with it? I'm a little weary of using 2 base gaskets might be inviting a vacuum leak.

[yaegerb]

My dome was engraved with the CC on it but i can't remember what it says. i'll pull it off and take a look.

If you can give me the bore, stroke and CC numbers off that head I can do a quick and dirty comp ratio for you.

This will be "ball park" only because it won't take into consideration any gasket thickness or decking on the cylinder.

are you still running this crank and bore and is that a stock stroke crank? If so, then all I need are the CC's off the head.

85 YZ250 crank shaft Hot Rods connecting rod & bearings
Wiseco YZ250 piston 68.5mm

[onformula1]

Cometic gaskets will make you any thickness you want.

Sent from my SM-G386T1 using Tapatalk

[El Camexican]

I seem to remember that someone sent you a thick base gasket for your engine build. If you didn't use it maybe you'd be willing to part with it? I'm a little weary of using 2 base gaskets might be inviting a vacuum leak.

Yes, that was courtesy of the esteemed Mr. 3 Wheel Drive, but it measured out to be the same thickness as the ones Versa puts in their kits. I would not be scared at all to lightly coat two with Yamabond and see what happens. At the very least you'll be able to determine if it revs higher and then you can go back to one gasket and get the head modified.

Speaking of nice guys, would you believe I'm wearing a Barrett Jackson shirt today?:w00t:

[NeverLift]

If you can give me the bore, stroke and CC numbers off that head I can do a quick and dirty comp ratio for you.

This will be "ball park" only because it won't take into consideration any gasket thickness or decking on the cylinder.

are you still running this crank and bore and is that a stock stroke crank? If so, then all I need are the CC's off the head.

85 YZ250 crank shaft Hot Rods connecting rod & bearings
Wiseco YZ250 piston 68.5mm

Bore is 68.5mm Stroke is 68mm it's an o-ring head so there is no gasket volume to calculate. I can hopefully pull the head tonight.

[yaegerb]

Bore is 68.5mm Stroke is 68mm it's an o-ring head so there is no gasket volume to calculate. I can hopefully pull the head tonight.

True, but I assume you are running a base gasket which effects squish, plus do you know if the base or head surface has been decked on the cylinder? That's another factor.

[NeverLift]

Yes, that was courtesy of the esteemed Mr. 3 Wheel Drive, but it measured out to be the same thickness as the ones Versa puts in their kits. I would not be scared at all to lightly coat two with Yamabond and see what happens. At the very least you'll be able to determine if it revs higher and then you can go back to one gasket and get the head modified.

Speaking of nice guys, would you believe I'm wearing a Barrett Jackson shirt today?:w00t:

I do have a spare base gasket. I figured you'd look good in red.

[NeverLift]

True, but I assume you are running a base gasket which effects squish, plus do you know if the base or head surface has been decked on the cylinder? That's another factor.

I bought the complete YZ motor and it looked like i was the first one to break it open. No silicone covering the cases, no stripped bolts and stock bore.

[cr480r]

I did run with the stock head and still had this problem.

^^I think a few missed this.

110 octane is not an issue for 15-16:1 UCCR on a two stroke.. 100 usually works from my experience.. Powervalved bikes can also trap a higher PSI for a given UCCR.. My kx250 trapped 245 with a thin base & stock dome lightly skimmed for .040 clearance.. They are around 220 stock. Cranking pressure only tells half the story unless comparing engines with fixed ports of similar duration.


You need to perform a UCCR to gauge your octane ratio. I can tell you my 250R was running like crap about 2 years ago and I performed the UCCR and found my uncorrected compression ratio to be 16:1 and should have been using 116 or higher octane...food for thought. My comp at the time was 218. My head ended up being 15cc's. That was a time bomb waiting to go off. BKM gave me an 89 TRX head to try and solved all my problems. The 89TRX head was stock at 23cc's.

All my modded 250's have been over 15:1... I have never used a dome smaller than 21cc with a domed piston. Even with a flattop piston you would have likely been over 17:1 with that 15cc dome.. that engine might have trapped 250-260psi on my gauge.. If your gauge doesn't have two functioning valves, and an adapter with 3/4" thread length it's gonna read low on a small engine.

[nstyle73]

Glad you could get the triples set up, they look great.

[NeverLift]

I rode it last night before dark. The shortened intake made it feel different like its breaking up not just flattening out. Next chance I get I'll do a plug chop and play with the jetting. Its about 40° warmer now than last time I rode.
I went from a br8es to a br9es and it was worse. Do you think its from being to rich?

[NeverLift]

This is the br8es 5 gear full throttle while its breaking up. 178 main. Before I cut the threads off I would have thought it was lean but down at the base its black. What y'all think? 230486

[onformula1]

Too lean for me, especially at WOT.

The plug trick was meant for a normal head, stock head 180 PSI MAX, not a Fuelie. :lol:

[NeverLift]

Too lean for me, especially at WOT.

The plug trick was meant for a normal head, stock head 180 PSI MAX, not a Fuelie. :lol:

If the plug trick isn't meant for high compression how do i go about jetting? Harry Klemm talks about using a tachometer. When the highest RPM is reached the jetting is correct. Whats your preferred method?

[yaegerb]

^^I think a few missed this.

110 octane is not an issue for 15-16:1 UCCR on a two stroke.. 100 usually works from my experience.. Powervalved bikes can also trap a higher PSI for a given UCCR.. My kx250 trapped 245 with a thin base & stock dome lightly skimmed for .040 clearance.. They are around 220 stock. Cranking pressure only tells half the story unless comparing engines with fixed ports of similar duration.



All my modded 250's have been over 15:1... I have never used a dome smaller than 21cc with a domed piston. Even with a flattop piston you would have likely been over 17:1 with that 15cc dome.. that engine might have trapped 250-260psi on my gauge.. If your gauge doesn't have two functioning valves, and an adapter with 3/4" thread length it's gonna read low on a small engine.



To each his own. I like running my R's around 185PSI, .080 squish, which puts me median 13:1 and using 93 at the pump.

[yaegerb]

I rode it last night before dark. The shortened intake made it feel different like its breaking up not just flattening out. Next chance I get I'll do a plug chop and play with the jetting. Its about 40° warmer now than last time I rode.
I went from a br8es to a br9es and it was worse. Do you think its from being to rich?


Got the CC's off that head yet?

[NeverLift]

Not yet I should have time this weekend.

[averysdad]

The plug is too lean? looks black to me.

I would also be interested in a way to check the jetting without cutting the plug?

How did you cut your.

[NeverLift]

Dremel and a cut off wheel.

[cr480r]

I like to measure the true volume at tdc with the head on the engine. The flat plate method of measuring the head is really only useful for comparing heads or measuring changes. Measuring the assembled engine tells the true story of what the engine really sees. The chamber, piston dome, squish, and gasket volumes are measured all at once.

[NeverLift]

I like to measure the true volume at tdc with the head on the engine. The flat plate method of measuring the head is really only useful for comparing heads or measuring changes. Measuring the assembled engine tells the true story of what the engine really sees. The chamber, piston dome, squish, and gasket volumes are measured all at once.

What method do you use to do this?

[yaegerb]

I like to measure the true volume at tdc with the head on the engine. The flat plate method of measuring the head is really only useful for comparing heads or measuring changes. Measuring the assembled engine tells the true story of what the engine really sees. The chamber, piston dome, squish, and gasket volumes are measured all at once.

So do I, but I can't do that with Neverlifts engine, unless he wants to ship it to me, thus the "ballpark" figure I mentioned earlier.

[yaegerb]

What method do you use to do this?

uncorrected compression ratio test, UCCR.

[cr480r]

What method do you use to do this?

I usually do it on the bench during assembly, but I am sure it could be done in the bike if you tore it down enough. I remove the head and rotate the piston to tdc. Usually it will stay put, but sometimes you might need to wedge the flywheel with something so crank doesn't rotate. Smear a layer of grease around the edge of piston to seal the ring lands. Install head and gasket and level engine. Pour known amount of liquid into spark plug hole from a graduated burrette and fill to bottom spark plug thread. Measure remaining liquid and subtract from initial quantity for the volume of cylinder. Add 1.2cc for spark plug and calculate compression. Example: 249+19/19=13.89

[onformula1]

If the plug trick isn't meant for high compression how do i go about jetting? Harry Klemm talks about using a tachometer. When the highest RPM is reached the jetting is correct. Whats your preferred method?

I type very, very slow...lol This info is interesting and well written it should help you out.

Eric Gorr Carb Tuning-

Carburetor tuning has the greatest effect on engine performance.

When a motorcycle manufacturer builds a bike, they usually install jets in the carb that are too rich. The manufacturers sell the same model worldwide, so they couldn't afford to install different jets in the carb to suit all the different climates and types of fuel. In addition to the climate and fuel, the manufacturer would also have to consider many other factors, such as the terrain and type of riding. And then there is the most important jetting consideration, the rider.

When I worked as a mechanic, I was in charge of jetting the bike over the course of the day. During morning practice sessions, the track was usually muddy and the air temperature was at its lowest point. I had to jet the bike rich for practice because the air density was greater and the mud put more of a load on the engine. Then I had to watch the rider and the bike perform on different sections of the track. I would go to the obstacle on the track that presented the greatest load on the bike, typically an uphill straight section. I'd listen to my engine and watch the rider. I'd listen for pinging or knocking noises or excessive smoke from the pipe. I would watch to see if the rider had to fan the clutch a lot and how my bike pulled in comparison to others. Getting feedback from the rider is difficult because they are concentrating on riding not the bike's performance. At a pro national there is one practice session, followed by a series of qualifiers and eventually two race motos. The time spacing of the riding sessions over the course of the day was such that I had to compensate the jetting two or three times. Otherwise, the bike would either seize from being too lean in the morning or run too rich for the second moto.

Race mechanics have different techniques for carb jetting. These techniques range from asking other mechanics what jets they are running to using precise measuring gauges to monitor the engine performance. In motocross races, where most of the riders are of equal skill levels, a holeshot in the start can mean the difference between a place on the podium and 30 minutes of roost in your face! The difference in horsepower between the bike that gets the holeshot and the bike that brings up the back of the pack may only be a few ponies! The race mechanic can give his rider an awesome advantage if he carefully monitors the carb jetting.

This section will give you insight into the carb tuning process, from diagnosing mechanical problems that mimic poor jetting to tuning tools such as gauges. It will also give you tips on a jetting method that I've developed called the "ride-and-feel" method," which I consider to be the best method It's a technique that I teach to all the riders I've worked with. You don't need any fancy tools, just the ability to make observations while you ride.


Identification Guide to Popular Carb Types

On two-stroke engines, several different model carbs have been used over the years, but there are basically two big carb manufacturers. Keihin and Mikuni are two popular brands of Japanese carbs used on nearly every dirt bike.

Keihin has several different models. The most popular ones are the PJ, PWK, and PWM. The PJ is used on Honda CR125, 250, and 500 models from 1985-1997 The slide is oval shaped and there are no additional pumps, its just a simple carb. In fact it's so simple that the choke and idle screw share the same jet. The PWK was the next step up from the PJ. The PWK has a crescent shaped slide and a separate idle circuit from the choke. The PWK is used on Kawasaki KX125, 250, and 500 models from 1990-97. The latest version of the PWK features a pump to supply extra fuel in the mid-range. The PWM is similar to the older PWK (no pump) and the overall length is shorter.

Mikuni has several different model carbs too. The original model VM had a round slide. There are many different parts available including needle jets of different diameters and jet needles with different taper angles and diameters. The next model was the TMX, which became available in 1987. It was a flat-slide carb, which offered a greater peak flow rate. The TMX was revised several times, becoming smaller with fewer parts. The TMS carb introduced in 1992 had no main or pilot jet. The slide and jet needle handled all the jetting. That carb worked great on 250cc bikes but never became popular. The PM is the latest Mikuni model. It features an oval crescent shaped slide and a very short body. That carb comes standard on Yamaha YZ125 and 250 1998 and newer models.

Carburetor Parts and Function
A carburetor is a device that enables fuel to mix with air in a precise ratio while being throttled over a wide range. Jets are calibrated orifices that take the form of parts such as pilot/slow jets, pilot air screw, throttle valve/slide, jet needle, needle jet/spray-bar, air jet, and main jet. Fuel jets have matching air jets, and these jets are available in many sizes to fine-tune the air-fuel mixture to the optimum ratio for a two-stroke engine, which is 12.5: 1.

Fuel Jets, Air Jets, and Throttle Positions

Three circuits control the air: the air-screw, the throttle slide, and the air jet. Four circuits control the fuel: the pilot/slow jet, the spray-bar/needle jet, the jet needle, and the main jet. The different air and fuel circuits affect the carb jetting for the different throttle-opening positions, as follows:
•
Closed to 1/8 throttle- air screw and pilot/slow jet
• 1/8 to 1/4 throttle- air-screw, pilot/slow jet, and throttle slide
• 1/4 to 1/2 throttle- throttle slide and jet needle
• 1/2 to full open- jet needle, spray-bar/needle jet, main jet, and air jet
(Note: On many modern carbs the spray-bar/needle jet and air jets are fixed-diameter passages in the carburetor body and cannot be altered.)
Basic Carb Service

Nobody likes to fiddle with a carb if they don't have to. Wedged in between the engine and frame with tubes, cables, and wires sprouting out like spaghetti, carbs are a pain to work on. Carbs require cleaning just like anything else, and some careful observations can save you big money in the long run. Start by pressure washing the bike, especially around the bottom of the carb where roost from the tires and oil from the chain accumulate. Take care when removing the carb; it's easy to damage the cable. It’s better to remove the sub-frame so as to enable unrestricted access to the carb. This will also make it easier to route the vent hoses in their proper positions too. When you remove the carb look at the vent hoses. Are they melted from heat or clogged with mud? If so that can cause a vapor-locking problem in the float bowl and make the engine bog.

Remove the top of the carb and disconnect the cable from the slide. Is the cable frayed or kinked? Is the rubber dust cover missing? If so then replace the cable. Now remove the float bowl, jet baffle (white plastic shroud around main jet), float and fuel inlet needle, and the air-screw. Shake the floats and listen for fluid that may have seeped inside. If so replace the floats otherwise the engine might suffer from constant fuel flooding. Check the fuel inlet needle. It has a Viton rubber tip and occasionally fuel additives and dirt damage the tip. Also check the spring-loaded plunger on the opposite end of the tip. If the spring doesn't push the plunger all the way out then replace it. Check the air-screw, there should be a spring and o-ring on the end of the needle. The spring provides tension to keep the air-screw from vibrating outward and the o-ring seals out dirt and water from entering the pilot circuit. Next check the bell mouth of the carb. Look for the two holes at the bottom of the bell mouth. The one in the center is the air passage for the needle jet and the other hole offset from center is the air passage for the pilot circuit. It's typical for those passages to get clogged with dirt and air filter oil. That would cause the engine to run rough because without a steady stream of air to mix with and atomize the fuel, raw fuel droplets make the jetting seem rich.

Once the carb is basically stripped down (pilot/slow and main jet still in place) you can flush the passages. Get an aerosol can of brake or carb cleaner from an auto parts store. Make sure you get the type with the small diameter plastic tube that attaches to the spray tip. Direct the tip into the airscrew passage. When you spray the cleaner you should see it flow out the pilot/slow jet and the air passage in the bell mouth. Next spray through the pilot/slow jet, look for flow through a tiny passage located between the venturi and the intake spigot. Spraying cleaner through these passages insures that the low speed air and fuel circuits are open and free flowing. The last area to flush with the carb cleaner is the slide bore and slide. Dirt tends to trap there, causing the mating surfaces to develop scratches that could cause the throttle to stick!

Just a small amount of water and dirt can get trapped in the tiny passages of the carb and cause havoc with jetting or even engine damage. How often should you service the carb? When it gets dirty! For example if you ride in muddy wet conditions you should at least check the vent hose. If the riding conditions are dusty and your air filter is covered with dirt, then it's a good idea to do a basic carb servicing.
Mechanical Problems

The process of jetting & changing air or fuel jets in order to fine-tune engines' performance is very simple. Jetting becomes complicated because mechanical problems sometimes mimic improper jetting. This causes you to waste time and money trying to correct the problem with expensive carburetor jets.

Before you ever attempt to jet a carb, make sure the engine doesn't have any of the problems in the following list. If you are in the process of jetting a carb and you are stumped with a chronic problem, use this section as a guide to enlightenment!

Crankcase air leaks & Air leaks can occur at the cylinder base, reed valve, or the magneto seal. Air leaks make the throttle response sluggish and may produce a pinging sound. That sound occurs when the air-fuel mixture is too lean.

Crankcase oil leaks & the right-side crankcase seal is submerged in the transmission oil. When this seal becomes worn out, oil can leak into the crankcase. The oil is transferred up to the combustion chamber and burned with the air-fuel mixture. The oil causes the spark plug to carbon-foul. This mechanical problem makes the jetting seem to be too rich.

Coolant-system leaks Coolant systems leaks commonly occur at the cylinder-head gasket. When the coolant leaks into the combustion chamber, it pollutes the air-fuel mixture and causes a misfire or popping sound at the exhaust pipe. Check the engine's coolant level frequently. Hondas and Kawasaki’s have characteristic coolant leaks because they use steel head gaskets. Yamahas and Suzuki’s use O-rings to seal the head and cylinder. Coolant-system leaks lower the engine's peak horsepower. It makes the engine run as if the air-fuel mixture is too rich.

Carbon-seized exhaust valves & the exhaust valves sometimes become carbon-seized in the full-open position. This mechanical problem can make the engine run flat at low rpm and make the slow-speed jetting seem lean. The carbon can be removed from the exhaust valves with oven cleaner. Clean the exhaust valves whenever you replace the piston and rings.

Blown silencer & when the fiberglass packing material blows out of the silencer, excess turbulence forms in the silencer and the turbulence causes a restriction in the exhaust system. This restriction makes the engine run flat at high rpm.

Broken reed-valve petals & the petals of the reed-valve can crack or shatter when the engine is revved too high. This mechanical problem makes the engine difficult to start and can also have a loss of torque. Expert rider should switch to carbon fiber reed petals because they resist breaking at high rpm. Novice riders should use dual-stage fiberglass reeds (Aktive or Boyesen). These types of reed petals provide an increase in torque.

Weak spark & when the ignition coils deteriorate, the engine performance will become erratic. Normally, the engine will develop a high-rpm misfire problem. Check the condition of the coils with a multimeter.

Clogged carburetor vent hoses & when the carburetor vent hoses get clogged with dirt or pinched closed, the jetting will seem to be too lean, so the engine will run sluggish. Always check the condition of your carburetor vent hoses. Make sure there is no mud in the hoses and that the hoses are not pinched between the suspension linkage.

Carburetor float level & when the float level is too low, the jetting will seem to be too lean, so the engine performance will be sluggish. When the float level is too high, the jetting will seem to be too rich.

Worn carburetor fuel-inlet needle & when the fuel-inlet needle wears out, excess fuel enters the float bowl and travels up the slow jet and into the engine. This makes the carb jetting seem to be too rich. Replace the fuel-inlet needle and seat every two years.
Jetting Shouldn't Be Scary!

Jetting is the process of making adjustments to the air and fuel jet sizes in order to fine tune the carburation to suit the load demands on the engine and make the power delivery consistent and optimum. Too much anxiety is placed on jetting. Most people just want to call me on the phone and ask what jets they should put in their carb. That's an impossible question because that the big dirt bike magazines attempt to answer just to increase readership.

People get confused because they read jetting specs in a magazine, put those jets in their bike and seize the engine. Any quoted jetting in this book is just a baseline. Most magazines don't list parameters for their jetting specs like; Brand new bike running with VP C-12 fuel with Silkolene oil mixed at 30:1 and a NGK 8 spark plug, ridden by a really slow lard-ass editor twisting the throttle on a hard-packed track. Some part numbers and jet sizes are given in the Tuning Tips section for models that definitely need certain jets in order to get the bike near the baseline. There is an old saying that says you can fish for a man and feed him for a day or teach him to fish and enable him to feed himself for life. Here is a quick lesson on how to jet your dirt bike.

The Ride and Feel Method

The most basic method of determining correct carburetor jetting is "ride and feel." This method requires you to determine if the carburetor tuning is too rich or too lean by the sound and feel of the engine. The first step is to mark the throttle body in 1/4-throttle increments, from closed to full open. Then, this method requires that you ride the motorcycle on a flat, circular course. To check the carb jetting for throttle positions up to 1/2 throttle, ride the motorcycle in second or third gear. Roll on the throttle slowly from 1/4 to 1/2 open. If the engine is slow to respond and bogs (engine makes a booooowah sound) then the carb jetting is too lean. You can verify lean jetting by engaging the carb's choke to the halfway position. This will make the air-fuel mixture richer and the engine should respond better. If the carb jetting is too rich, then the engine will make a crackling sound; the exhaust smoke will be excessive and the engine will run as if the choke is engaged. Careful engagement of the choke can help you determine if the jetting is rich or lean. Another important tip is to just change the jets one increment at a time, either rich or lean, until the engine runs better. Most people are afraid to change a jet because they think that the engine will be in danger of seizing. Believe me, one jet size won't make your engine seize but it could be the difference between running bad and running acceptable.

To check the jetting for throttle positions from 1/2 to full open, ride the motorcycle in third and fourth gear. (You may need to increase the diameter of the circular riding course for riding in the higher gears.) Check the jetting in the same manner as listed above. The carb jets that affect the jetting from 1/2 to full throttle are the jet-needle, main jet, power jet (electronic carbs) and the air jet (on four-strokes).

If you want to take this technique out to the racetrack, you can test the pilot/slow jet when accelerating out of tight hairpin turns, the needle clip position on sweeper turns and short straits, and test the main jet on the big uphill or long straits. Of course be careful if you try to use the choke technique because you could lose control when riding one handed.

Jetting for Riding Techniques

Certain types of riders require jetting to compliment their technique. For example beginner minibike riders will need slightly richer jetting on the pilot/slow jet and the needle clip position to mellow the power band and make it easier to ride. Conversely desert racers who hold the throttle wide open for long periods of time need rich main jets to compensate for the high load.

The Weather Makes The Biggest Difference!

The weather can have a profound affect on the carb jetting because of the changes in air density. When the air density increases, you will need to richen the air-fuel mixture to compensate. When the air density decreases, you will need to lean-out the air-fuel mixture leaner to compensate. Use the following as a guide to correcting your jetting when the weather changes:
Air temperature & when the air temperature increases, the air density becomes lower. This will make the air-fuel mixture richer. You must select jet sizes with a lower number to compensate for the lower air density. When the barometric pressure decreases, the opposite effect occurs.

Humidity & When the percentage of humidity in the air increases, the engine draws in a lower percentage of oxygen during each revolution because the water molecules (humidity) take the place of oxygen molecules in a given volume of air. High humidity will make the air-fuel mixture richer, so you should change to smaller jets.

Altitude & in general, the higher the altitude the lower the air density. When riding at racetracks that are at high altitude, you should change to smaller jets and increase the engine's compression ratio to compensate for the lower air density.
Track Conditions and Load

The conditions of the terrain and the soil have a great affect on jetting because of the load on the engine. Obstacles like big hills, sand, and mud place a greater load on the engine that requires more fuel and typically richer jetting. In motocross, track conditions tend to change over the course of the day. Typically in the morning the air temperature is cooler and the soil wetter requiring richer jetting. In the afternoon when the temperature rises and the track dries out, leaner jetting is needed in order to keep the engine running at peak performance. Other changes for mud and sand riding might include changing to a lower final-drive ratio (rear sprocket with more teeth) to reduce the load on the engine and help prevent it from overheating. Advancing the ignition timing will make the engine more responsive at low to middle rpm.

Fuel and Oil Mixture Ratios

When we talk about the "fuel" in the air-fuel mixture for a two-stroke engine, we are really talking about a mixture of fuel and oil. If you richen the pre-mix ratio (20:1 as opposed to 30:1) there is more oil and less fuel in the same volume of liquid, which effectively leans the air-fuel ratio. And this fact gives the clever tuner one more tool to use when the correct jet is not available or when none of the standard jets are exactly right. You can richen the jetting by slightly reducing the pre-mix ratio (less oil). You can lean the jetting by increasing the pre-mix ratio (more oil). The best part is that changes in the pre-mix ratio affect the jetting over the entire throttle-opening range, but the changes in ratio must be small to prevent excess wear from lack of lubricating oil or fouled plugs from too much oil.

Pre-mix oils are formulated for a fairly narrow range of pre-mix ratios. You should examine the oil bottle for the oil manufacturer's suggestion on the pre-mix ratio. All production two-stroke dirt bikes have a sticker on the rear fender suggesting that you set the pre-mix ratio to 20:1 That sticker is put there for legal purposes. Always refer to the oil manufacturer's suggestion on pre-mix ratios. In general, small-displacement engines require a richer pre-mix ratio than do large-displacement engines because smaller engines have a higher peak rpm than larger engines. The higher the engine revs, the more lubrication it requires.

Tuning Gauges
There are three types of gauges that professional tuners use to aid carb jetting:
1. Relative-air-density (RAD) gauge
2. Air-fuel (AF) ratio meter
3. Exhaust-gas-temperature (EGT) gauge

The following is a description of how each gauge functions and their advantages.

RAD gauge: This is the best gauge for dirt bikes because of the convenience. The gauge is no good unless you get the jetting perfect once. The RAD gauge provides you with an indication of how much the air density changes, helping you compensate for the affects of changes in the air temperature, altitude, and barometric pressure. The gauge is calibrated in percentage points. Once you set the jetting with the ride and feel method, you can set the calibration screw on the gauge so the needle is pointing to 100 percent. When the air density changes, the RAD gauge will show the relative percent of change. Using a calculator you can multiply the percentage change shown on the RAD gauge by the jet size and determine the corrected jet size for the air density. The pilot/slow and main jet have number sizes that correlate with the RAD gauge, but the needle clip position can only be estimated. Normally for every two main jet increments, the needle clip must be adjusted one notch.
AF ratio meter: The AF meter measures the percentage of oxygen in the exhaust gasses, and displays the approximate air-fuel ratio of the carb. The gauge displays AF ratios from 10-16:1 The optimum AF ratio for a two-stroke engine is 12:1. The AF gauge utilizes a lambda sensor that is inserted into the center of the exhaust stream, approximately six inches from the piston in the header pipe of a four-stroke and in the baffle cone of a two-stroke engine. A permanent female pipe fitting (1/4in.) must be welded to the side of the exhaust pipe in order to fasten the sensor. The weld-on fitting set-up is also used on the temperature gauges, and the fitting can be plugged with a 1/4in. male pipe fitting when the gauge is not in use. This gauge is ideal for four-stroke engines.

EGT gauge: The EGT gauge measures the temperature of the gasses in the exhaust pipe by means of a temperature probe fastened into the exhaust pipe, six inches from the piston. This type of gauge enables you to tune the carb jetting and the pipe together, taking advantage of the fact that exhaust pipes are designed with a precise temperature in mind.

An exhaust pipe is designed to return a compression wave to the combustion chamber just before the exhaust port closes. Most pipes are designed for a peak temperature of 1,200 degrees Fahrenheit. Most dirt bikes are jetted too rich, which prevents the exhaust gasses from reaching their design temperature, so power output suffers. Sometimes just leaning the main jet and the needle-clip position makes a dramatic difference.

Digitron is the most popular brand of EGT gauge. It measures both EGT and rpm. This gauge is designed for go-kart racing so it’s not suited for wet weather conditions. It is designed to mount on the handlebars. That way the rider can focus in on it. Once you have performed the baseline jetting, send the rider out on the bike with the EGT. The rider observes the EGT to give you feedback on the necessary jetting changes. Once the jetting is dialed, we use the tachometer to check the peak rpm of the engine on the longest straight of the racetrack. For example, if the peak rpm exceeds the point of the engine's power-peak rpm, then change the rear sprocket to a higher final-drive ratio (rear sprocket with fewer teeth) until the rpm drops into the target range. An EGT gauge is ideal for dirt track bikes and go-karts, where peak rpm temperature is critical.

[NeverLift]

She's pulling hard from top to bottom now.

My exhaust valve wasn't opening while i was riding. I took the cover off in the garage, warmed up engine, slow rev PV opens. I take it for a ride, hang my head over and watch, doesn't open, reach over and lift up and she takes off!! Back in the garage I pull the clutch cover, the gear on the PV governor is backwards. I looked at it and it was so obviously wrong i'm thinking what IDIOT put this together well that idiot was me. Back together she stumbled from mid to top, pulling the choke at both positions only made it slightly worse (182 Main). after 5-6 jetting changes I ended up with a 175 main, needle in the highest (leanest) position and 1 1/4 turns on the pilot. The last thing i did before i put it away was a 2nd gear launch up thru 5th and she pulled hard and smooth from top to bottom. It rip's right thru 1st, 2nd and 3rd. 4th, 5th seem to never end a 6th while my yard isn't big enough for that one(10 acres). Next up i'll retard the timing 1mm at a time like onformula1 suggested. A set of HT carbon tech reeds are on the shopping list.

Thanks for all the help guys it is much appreciated.

I pulled the head before all this and the engraving says YZ250 PUMP no cc listed. I have plexiglass but no way to accurately measure liquid. Graduated burrettes are only $22 on amazon so i'll order one. The piston to head clearance at the squish band is .055 inches. I did this using soldier on top of the piston and turning the crank over by hand 3 separate times.

[Red Rider]

Your Tri-Z is looking very nice. I'm glad you're getting the bugs worked out, and she's starting to perform like she looks. Keep the reports coming in.

[NeverLift]

Thanks for all the compliments guys.

[NeverLift]

I went for a ride yesterday near Turtle Lake, WI. 40 acre park with big berms, minor jumps and some long straights thru the pine trees. The Z ran great. It pulls much harder than my " phase 2 wrench report" Z motor. I can definitely tell the lighter flywheel no lugging it a gear high anymore I don't mind feathering the clutch but would prefer not to. The new forks and swing arm are fantastic soaked up everything I dished out with ease. I am very happy with the way everything turned out. Trikefest may be in my future. It will be a last minute call like everything else.
After about 3 hours my foot peg mount broke off. This had been repaired before but not well. I'll have to reach out to Raffa and see it he still sells that nice little weld in plate. In the interim I have a red frame just sitting in the shelf so I'll be swapping it out.

[NeverLift]

Steering head bearings came in for my red frame. Hopefully i can get the frame swap done tomorrow.
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hatc200x1 I seem to remember you ride Moose Lake, General Andrews area. Send me a PM next time you go i'll try to make it up. All my riding buddy's are turd's and always have an excuse why they can't ride.

[NeverLift]

Ready to ride again. I finished her up last night. I'll leave it like this for the summer and get it powder coated during winter.
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[NeverLift]

Put another 3 hours on her today and I love this thing. Front Suspension is great I need to send the rear to Milner its a little soft for my fat ass. Power is fantastic. I lined up against my 440EX and it blows it away but that's not saying much. I'm going riding next Saturday with a raptor 700 so I'll line up with him and see how it goes.

[NeverLift]

I went riding Saturday at Snake Creek Trail and everything worked flawless. Only picture I have is at the truck. These trails are fun, tight and technical with hill climbs and jumps(supposed to be speed bumps) all over the place. I was hoping to drag race my buddies Raptor 700 but there was no spot to run them. I did run into a group with 3 trikes(350X, 200s and YTM200). It was funny they walked up and were calling my trike the Unicorn.

http://www.dnr.state.mn.us/ohv/trail_detail.html?id=21

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Looking like I'll be able to make Trike Fest. I'll probably park it till then.

[NeverLift]

I went to a buddy's cabin this weekend. One of my favorite places to ride. 1000 acre property that was logged on and off so there are 10 foot wide trails through out. They just fixed their big brush mower to trim the trails so it's a little sketchy when your off the main trail. Here is a short ride I went on by myself nothing special maybe a little boring. Next time I go up we'll bring the dozer on the track and smooth it all out again. I'm want to see if he'll host a trike ride there when i finish his 200X, there's plenty of room for camping.


https://www.youtube.com/watch?v=ilkJr0ql1hk&feature=youtu.be

[El Camexican]

Sounds pretty peaky. I figured the power valve would add more the over rev. I look forward to hearing run it in person. I didn't look back through the entire thread, but do you know the cranking compression on the engine?

Now let's discuss that little doggie at the beginning of the video. What the heck are you feeding that thing! Poor little guy just wanted to go for a run and sweat a few pounds and you totally blew him off :lol:

[Red Rider]

Sounds good Neverlift! It looks & sounds like it pulls pretty hard. I'm glad you got the bugs worked out of it, so now you can enjoy the fruits of your labor, and start staining your Fruit of the Looms. :lol:

[NeverLift]

You leave jack alone, that's solid muscle if I let him come with I can't keep up.
230 psi right after I put the head on. I have 5 tanks of 110 thru her now so I'll check again tonight. That's with the "pump gas dome" my ass. I'm going to turn my other dome down to be 180psi.
I pulled the plug after that ride and it was black. Hot and humid about 80° and noticeably slower than my last ride at 65°. I'll drop her down for the hot months.



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[NeverLift]

Still at 230

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[El Camexican]

I wonder if the PV adds to that number when you're kicking it over?

[fieldy]

Wow, what a paradise! I saw 2 small rocks and 3 mud puddles. Nice video, i enjoyed that.

[NeverLift]

I wonder if the PV adds to that number when you're kicking it over?
I think it would have to. Next time I have the head off I'll measure the port height closed vs open. My piston to head clearance is .060"

It is paradise. My wife and I spent our honeymoon up there with the wheelers.


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[onformula1]

Great Video!, Thank You for sharing and it looks like a great place to camp & ride, lucky guy.

We have a area fairly close to us that reminds of that area, a bit less grass and more trees but it reminds me of it.

I would leave the jetting, any bike or trike that has that much power and snap with a black plug is a Winner! I have never been a fan of the creamy mocha colored plug quest on a two stroke.

You will have a wider spread of power with less compression and it sounds like you have a dome to play with.

The power valve has no effect on compression tests for several reasons.

[NeverLift]

Here is a picture of the plug and gauge last night.

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[/QUOTE]I would leave the jetting, any bike or trike that has that much power and snap with a black plug is a Winner! I have never been a fan of the creamy mocha colored plug quest on a two stroke.[QUOTE]
You say leave it. i'll leave it.

[NeverLift]

Sounds pretty peaky. I figured the power valve would add more the over rev.
I have not played with the timing yet. It's just a hair retarded from stock.

[The_Steve_Man]

Looking good! When you get it running right, you an juice box can come down for rampage.

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[NeverLift]

Been awhile. I've got all the kinks worked out. She handles great, pulls hard and I love it. I don't believe the PV added too much but it's fun for it's unigueness. This summer I race MX at trike fest, 2 TT races localy and trail rode a hand full of times. Currently i'm setting her up for ice racing. Here are some of the videos.

https://www.youtube.com/watch?v=5kDuCr3cNAQ
https://www.youtube.com/watch?v=QJ8YI3naozw
https://www.youtube.com/watch?v=9HH1P1Wt3jY

[brandonlowe2]

This is an amazing build.... I am going to use several of your techniques on my build... hope thats ok! I hope I get to see it in person one day

[NeverLift]

This thing just keeps changing. TT is the current flavor. I'll be lowering it 2 inches it the rear tonight. Top mount tank will be delivered Monday. I'm running the yellow plastic until I can find a left rear fender stay.
242987242988242989

[NeverLift]

Picture's of the tank Fast Eddie had designed.
https://www.spunaluminumgastanks.com/
242990242991

[NeverLift]

244768244769
Luck getting to the TT races has been horrible so back up she goes for trail riding.
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Top Mount and Clutch basket work great.

[Ghostv2]

I hope you carry extra gas trail riding with that tank lol. How much does it hold?

[NeverLift]

Tank is .9 gallons and 2 1/2 on the 6 pack rack.

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[NeverLift]

So much fun at Little Sahara. 247704247703247705

[NeverLift]

Here is a race from this summer. Souix Falls, SD this track is amazing.

https://www.youtube.com/watch?v=23teGiccxL4&t=221s

[NeverLift]

I've been swapping suspension back and forth on this thing depending on where i ride for the past 2 years. It's time to just build a second. #1 TT/Ice racer #2 will be a trail/dune machine. I've got all the parts needed the frame was my only setback. So let the fun begin. I cut off all the unneeded mounts for the race trike and i'm fixing the foot peg mounts.

248411248412248413248414248415

[NeverLift]

Little practice out on the ice yesterday.
https://www.youtube.com/watch?v=qjeBAmXt9X8&feature=youtu.be

[NeverLift]

Couple more goodies.
250260250261

[NeverLift]

Raffa foot peg mounts welded on, unneeded mounts ground off, fresh paint and shes ready for a frame swap. All 3 hubs and the rad mounts will get this same blue any little parts will get shot with black. Gonna hit all aluminum on the buffing wheel. Mount up the studded tires and i'll be ready for ice racing season.
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[NeverLift]

Racing from Haydays this fall in MN. I got 3rd both days behind Daryl Rath and Lynn Sather.
https://www.youtube.com/watch?v=WYIBtSlfu2s&feature=share

[NeverLift]

Bye Bye red frame.
256075

[Red Rider]

I like it, even though it's looking a bit Suzuki-ish!

[3Z with Fangs!]

It's going to be sweet man!

[NeverLift]

257778
Current Flavor.

[El Camexican]

Looks mean! What’s the aluminum thing on my throttle side of the bars?

[NeverLift]

257787 257788
Little brake reservoir made on my lathe. I run 09 GSXR brake master and clutch perch.

[Triptherip]

Hey. Beautiful bike you built. Can you please tell me what forks those are, how much have you shortened them, and what triple trees you are running?

[NeverLift]

85 tri-z cases
86 tri-z transmission
85 YZ250 crank shaft Hot Rods connecting rod & bearings
85 YZ250 Cylinder (ported & polished cylinder)
Sprock Head
Wiseco YZ250 piston 68.5mm
38mm Keihin PWK
Boyesen Power Reeds
LRD Pipe
Unknown silencer
Complete chassis All Balls bearings
2001 CR125 Forks
Works quadcross rear shock
Lonestar +2 axel
Metal Tech +3 Swingarm Banshee round carrier
Hall Performance Triple Tree's
2001 CR125 Forks
2001 CR125 Froks -6"
Billet Thermostat Eliminator
Unhinged ATV Foot Pegs
250R Front Hub
10" 250R Wheel
Hoosiers on All 3
Adjustable Rear Lowering Link
Top Mount Tank