View Full Version : How to power valve your Tri-Z

Derrick Adams
01-31-2005, 09:24 PM
Well, I thought i'll go ahead and start this thread for anyone that's curious.

I've started my engine assembly and i've been documenting it.

In case anyone wonders why you would do this, it has been said that this drastically improves overall performance of your engine, giving it more torque thru-out the powerband.

First your going to need to locate a complete 83-87 YZ250 engine. You can either use the whole YZ engine or just the components related to the power valve, which is what I did. It works the same either way.

The first part neccessary to swap is the crank gear, if you choose to use the Tri-Z lower engine. The gear off the YZ is a double gear used to operate the power valve governer.

Next you need to install a bearing in the Tri-Z case for the governer. These are still available from Yamaha for $11.00

Derrick Adams
01-31-2005, 09:28 PM
Here's a couple shots of the YZ and Tri-Z cylinders beside each other. Notice the volume difference in the intake.

The intake is also angled slightly to the left, which is an issue we will deal with later.

Derrick Adams
01-31-2005, 09:37 PM
Now we'll address the modifications neccessary to adapt the Tri-Z clutch cover for the power valve governer.

First a bearing needs to be installed in the clutch cover to support the governer. These are still available from Yamaha for $11.

Then you must knock out a punch plug from the Tri-Z cover. All of the casting and machining to accept the power valve equipment is done from the factory. You need to simply install it.

Once the plug is out you'll need a seal to replace it. This is still available from Yamaha for $6.00. Then just install the rod assembly and governer from the YZ engine and cover into the Tri-Z cover.

01-31-2005, 09:44 PM
This thread has been done before. Can't wait too see the finished product!!! Wish i had one.

Derrick Adams
01-31-2005, 09:44 PM
That's where i'm at so far. I'll install the cylinder and finish it up later this week. Still waiting on the piston. I'll also cover how the install goes into the bike.

01-31-2005, 09:55 PM
Very informative Derrick! Great thread!

01-31-2005, 10:11 PM
I do not suppose you have a printable form of instruction sheet.

Red Rider
01-31-2005, 10:12 PM
Looks much easier to adapt the YZ cylinder & governor to the Tri-Z, than it was to adapt the CR cylinder & governor to my ATC 250R. Now every Tri-Z's gonna be powervalved! Cool thread Derrick!

01-31-2005, 10:14 PM
Which way does the stock YZ kicker go? Front or rear?

Derrick Adams
01-31-2005, 10:47 PM
Kicks rear. When I do my other YZ engine, I'm going to do it the opposite way and use the YZ bottom end. So, i'll be switching the kicker gears. It will be a couple weeks before I get to that though. I'll add all that info to this thread as well.

01-31-2005, 11:15 PM
So it is not neccassary to use the whole Tri Z side cover on a YZ bottom end?

01-31-2005, 11:22 PM
the easiest thing to do ,like i did, was swap the whole top/ bottom in place, my intake is straight in, yours it at an angle..mmmm....great information for the ones with questions with this swap, next i think im going for the 426 or 450 thumper in one , problem is those engines cost way too much

01-31-2005, 11:27 PM
What year motor you got Derrick? Mine is an 87 and its slanted to. I know 88 on up went back to 6 pedal reeds, and had a straight intake.

Derrick Adams
02-01-2005, 12:47 AM
Both of mine are 87's.

02-01-2005, 01:02 AM
Good stuff Derrick! Now hurry and finish it! :p

02-01-2005, 01:17 AM
Man, that is an awsome thread. I love technical stuff.

Derrick Adams
02-02-2005, 10:40 PM
I received my new piston kit today. The rest of the parts should be in by friday, so i'll add to this post sometime this weekend.

Derrick Adams
02-04-2005, 10:02 PM
Ok. Here's the cylinder installed. Notice the vacuum port installed in the cylinder for the fuel pump. I chose to use a standard threaded one from Napa, just tapped it and screwed it in.

Derrick Adams
02-04-2005, 10:10 PM
Now here's the first real "Problem" I've ran into.

My engine didn't come with an intake or reedcage, so I picked one up on ebay...well this is supposedly off an 83, which obviously won't work on the 87. (the intake would fit but there was NO WAY that reed cage was fitting!)

Next Picture: Here's my quick solution. I carved an adapter out of some plate aluminum and just reused the stock Tri-Z intake and reed cage. Wonder how it will work with the boost box hooked up?!?

Last Picture: Here's another shot of the adapter. I will probably move this to my trail bike later and use something else on this bike. You can see in the picture the nest issue of fitting a filter on the carb!

I'll finish up the engine on Monday. Watch for more pics.

02-05-2005, 12:23 AM
ill buy that part from you , the 83, like mine, has that huge 8 petal reed cage, and a 38-40mm carb willl not fit in the little 32mm intake,if it does by chance, be forewarned, you WILL run lean on top end,even with a 580 main!

Derrick Adams
02-05-2005, 09:49 AM
What's the theory behind the intake making the engine run lean? I'm running a 37mm in the stock intake right now with no issues. I'll keep that in mind, but I'm going to see if it fits in my other engine first. I may be able to just switch them around.

I can see right now, that a custom intake will have to be built to run the stock airbox set-up on the trail bike. That thing is seriously kicked over to the left.

02-05-2005, 08:53 PM
i see , i thought you might have a 32mm carb going on that intake, a 37 will be fine

Derrick Adams
02-13-2005, 06:43 PM
Just an update. I fired the bike friday night, seemed to run fine. Today I did a soft 1/2hr ride to break in the rings and it seems to be doing well. I'm working on getting an air filter installed and will post up some more pictures tomorrow. I have had 2 intakes on it now. Still not satisfied so I am going to build a custom aluminum one, soon.

Derrick Adams
02-26-2005, 01:57 PM
Here's the last two pictures of the air filter and adaptor I went with.

All in all, I spent $250 total on the engine swap, and don't feel it was a worthwhile investment. I guess it really only cost me about $150 extra, because I needed to freshen the top end anyhow.

I wouldn't recommend spending extra cash just to do this swap, because it really didn't show me any performance gains. Unless something changes it was a big disappointment.

I already had the DG pipe and silencer, 36mm carb, Uni filter, and Boyessen reeds. Everything stayed the same with the exeption of the powervalve topend and it feels the same.

The only thing left to try would be to swap the flywheel, as the Tri-Z flywheel is huge compared to the YZ.

This thread is officially done!

02-26-2005, 11:53 PM
thats very odd... they have 8 hp more than a stock z, maybe the 83 motor like mine has more hp, i noticed a night and day difference, my stock motored z had a new top end and i went up two teeth on the front sprocket with the powervalved z , and the powervavled z still out runs the stock z on bottom end pull and alot more on top, you must not have it dialed in right, i run a 40.5 mm carb, i tried a 38mm, and it had NO POWER!!

02-27-2005, 12:02 AM
Yeah man, you got something seriously wrong. My 87 is almost completly stock, and it will walk all over most anything its up against (besides all out high dollar drag banshees)

I agree with 03 orange shee, you dont have something dialed in right. I was running a 38mm carb on mine, but it also has the pvl style ignition.
My Z with the 87 YZ motor is a good 10-12 bike lengths ahead of a stock 85 Z in the 300 ft drag races... if your not seeing the same, you got something not working correctly.

02-27-2005, 12:16 AM
so 03 orangeshee...is yours an 87 top end then?

Derrick Adams
02-27-2005, 12:45 PM
Here's what i'm saying guys, I only changed to the powervalve set-up. Nothing else. So it's probable that the whole YZ engine has many different benifits over the Tri-Z, not all in the powervalve assembly. I think that I'll switch to a bigger carb next, since that's an easy swap. Then i'll try the flywheel/ ignition swap.

Brandon and I are going to go race them today, so i'll have a better idea. Before his R and my Z were dead even. It was 50/50. 10-12 bike lengths in 300 ft is HUGE! I'm sure I would be able to feel that. I'll let you know how that goes, as well as any differences in carb swaps and flywheel/ignition swaps. Then we'll know exactly where all the power is coming from.

02-27-2005, 03:09 PM
10-12 bike lengths in 300 ft is HUGE! I'm sure I would be able to feel that.

Oh yeah, you'll be able to feel it!! And your face will show it!! The smile will be permanent for a few days... If all else fails, yank that top end off, and drop that YZ motor in like I said you should of in the first place. If it still runs like the Z motor, something is messed with the top end.

02-27-2005, 03:23 PM
mine is a 83 stock yz motor, no porting what so ever, and like chainsaw says, very big grin on your face after riding, it feels like i went from a blaster to a banshee, there is that much difference, 8 hp is alot on a light three wheeler 32 vs. 40 , i went up two teeth on the front sprocket(15/40) and it i still cant keep the front end down through 4th unless i let off the gas , the 13 tooth has too much tire spin, or i couldnt crack it for fear of flipping over backwards

02-27-2005, 06:25 PM
dang, sounds wicked, but then you have to run the backwards kicker dont ya? or can you use the tri-z case on it??

02-27-2005, 07:02 PM
Use the Tri Z kick gears, or mod the YZ ones and wah-lah.

Derrick Adams
02-27-2005, 09:14 PM
I ran Brandon 9 times. Everytime I beat him by a couple bike lengths, but he was having traction problems and I wasn't. I'm running a 13 tooth front sprocket, and you have to slip the clutch to take off. So obviously there are some tuning issues.

I'm going to swap out my DG pipe next. Every since I put that damn thing on it has no low-end sack. I have that other pipe I just bought, i'm going to try on it. As well as a real nice stocker. When I ran my stock pipe on the Tri-Z engine, it ripped! TONS of torque, but I stuck with the DG because it cost me soo much...

I used my Tri-Z bottom end because I know the tranny is good, as far as I can tell the crank and gears are all the same, so if I swap out the flywheel and ignition I should be right back to stock YZ. I also need to find a bigger carb, I'm sure that 36mm is too small.

Both of you guys are running the YZ ignition right? I know on the 250R the big upgrade is the CR ignition, so that maybe the same case here. Also, there is a HUGE difference in size of the flywheels. I'll get that swapped out toom and see what it does.

I'll do some testing tommorrow. See if I can get this thing running better.

02-27-2005, 09:48 PM
i have the yz ignition setup, but run a lightened z flywheel, i ride at night sometimes, and the dg is all bottom end, they are good for bottom to mid, try a jemco pipe for top end, they are left side outframe for top end hit, and they are in houston texas,the only drag pipe for a z still made TODAY!!!!

Derrick Adams
02-27-2005, 10:42 PM
I'll tell you what, everybody says the DG pipe is low-end to mid. That's why I bought one. But mine isn't! I think someone forgot to add the low-end to it! LOL.. It bogs down low, no matter how I set up the carb and hits like gang busters in the mid range, then peters off again up top. (although I did notice more top end with the PV motor)

The pipe actually isn't too bad for drag racing, because it's real predictable off take off. I can pretty much lean forward, revv it alittle and dump the clutch. By the time the pipe hits, the bike is rolling fast enough not to spin and it just carries the wheel in 2nd. Never has a problem spinning, although it does hook too good some times.

We'll see how this other pipe works out. I really need more low-end to race MX with this thing. It just doesn't pull out of the turns at all.

How are you running at night with no headlight wiring? The YZ doesn't have any of that does it?

02-27-2005, 10:54 PM
Im running a tryke ignition on mine.. its a PVL style, no provision for lights, and if you ever come across one..... get it! I wish I had a couple more.

02-27-2005, 10:55 PM
You werent on it much at Galion, but did you think mine had any low end?

Derrick Adams
02-28-2005, 08:44 AM
I don't want to talk about it!!!!!

02-28-2005, 10:19 AM
I don't want to talk about it!!!!!

LOL! I give all the credit to a top end job done at Wiseco by people who really know what they are doing, and do a job complete and right. I had no "performance" work done, but they cleaned up the porting as a standard part of a resleeving job. When I rode yours I thought it was pretty good at the bottom, but that was after riding mine with a shot top end for quite a while. Most DG pipes for most models are pretty much stock replacements. I sure wouldnt characterize it as "low end pipe" though I did see some low end gains on my TriZ, nothing drastic though.

I probably should have rode a lap on yours at the HS. If you werent getting low end, I dont think it was a pipe problem for your original TriZ motor. I dont know much about the powervalve motor, but I do understand how they work, (basically a varaible exhaust) and just based on theory, I would think that a pipe designed for a non-powervalved motor would give different results on a powervalved motor. Since a powervalve cannot increase exhaust flow, and can only restrict it, which is where your low end comes from, I would think a top end pipe would be a better place to work from on a powervalved motor for overall best results. Again, I have no experience with it but it sounds logical to me. Id give that unidentified pipe a try, just to see what happens. It appears to be low end/midrange oriented. I would then try the stock pipe, which is petty much a top end pipe and see what happens. Only experimeentation will tell, but I think your going to get your best results from a top end pipe, even on low end.

02-28-2005, 11:15 AM
has any one tried just usin the YZ pipe on the PV YZ motor?

02-28-2005, 12:23 PM
has any one tried just usin the YZ pipe on the PV YZ motor?

Works great on a YZ, but its not an option as soon as you put that motor in the TriZ chassis.

02-28-2005, 09:20 PM
i did, it fits, it rubs the frame alittle, bolts to the muffler, but i didnt like the paint on my frame getting rubbed off

03-01-2005, 12:42 AM
so then what do you guys run on the PV motor? top end pipes?

Derrick Adams
03-01-2005, 08:50 AM
We all run the same DG pipe. Probably the only stock shape pipe still made for the Z.

03-01-2005, 07:23 PM
for woods i run dg, for drag i run jemco, this is tri-shees' bike , not mine

03-01-2005, 08:08 PM
I ran a hybrid on my YZ motor. It was a cross between a PSI and something else that I cant remeber the name of. It was actually made for a 370 motor I had.

08-26-2005, 11:16 PM
Dose anyone know if you can use the YZ side case and kick backwards on the tri-z without hitting the frame? also, where did you manage to find a 40.5 mm carb? flatslide? bored out i would assume?

Jason Hall
08-27-2005, 02:36 PM
Eddie sanders racing sells a 40.5mm carb. It is a pwk d-slide bored to 40.5mm. I have 2 of them on my old srx sled, they are sweet carbs. From my experiance with my honda's they work better on the big bore motors.

08-27-2005, 04:25 PM
why not just put the whole YZ engine in there?

1985 TriZz GuyY
12-30-2019, 12:39 PM
How did you get your intake to line up. If your just swapping the top end? I want to keep my headlights

El Camexican
12-30-2019, 07:15 PM
How did you get your intake to line up. If your just swapping the top end? I want to keep my headlights

Regarding the intake angle, you would need to find an older cylinder if you want it to line up with the existing plumbing. I think it’s only the 1983 YZ 250 that has a straight intake and still bolts to the Tri-Z cases. If you have a 84 or newer cylinder you’ll either have to run a pod filter, or plum something up like Neverlift did on his PV build. You can find that build with the site's search feature.

As far as the lights are concerned, if you have a Tri-Z crank and bottom end you’re good to go, but if you’re using a YZ bottom end and must have lights, you’ll have to either install a Tri-Z crank, or at the very least the left side of the crankshaft which accommodates the Tri-Z's electrical system.