Rebuilt, now gray plug?

[yzboyx]

I just rebuilt my tri-z. I used the same jug, just honed it out. I put everything back the way it was. I ran it up the road and did a plug chop only to find the plug is a nice light gray color. Why is it running so lean? I'm using the same fuel mixture of 32:1. Is there another way to richen it up besides rejetting. Can I change the fuel mix to 20:1? Would this be enough? Any thoughts or suggestions....

[Bryan Raffa]

you can lower the clip on the needle and fine tune it with the air screw stock is one turn out the easeyst ways is to increase oil

[Kintore]

Did you fully break in the motor? Did you use a new piston or the old one with the same rings?

[Bryan Raffa]

you should increase your oil anyway with a new top end!!!!!!

[bbbanshee rider]

First off did you get it bored did you add a pipes did you do anything to get more aire in the motor if so you should rejet changing the gas/oil ratio will just be harder on the ring in youre motor. rejeting a larger main insint difficult.



1999 highly mod banshee

[yzboyx]

I have run it through about 5 or 6 heat cycles. Starting it up and driving for about 15 minutes each time, never staying at one rev. I used a new piston with new rings. The reason for the rebuild, I forgot to oil the K&N filter. Then took it out to the sand bars. It's amazing what a little sand will do to the side of a piston! Learned my lesson. ALWAYS OIL AIR FILTER!!!

I thought the needle clip and the air fuel screw would not affect wot. But I'm definately no expert! Thanks for any suggestions!

[yzboyx]

No, I already had a dg pipe on it. Nothing was changed, but a new piston and rings.

[Bryan Raffa]

moveing the clip down has the effect of pulling the needel further out of the jet thus richening it moveing it up leans it do it one step at a time if you get all the way down and no effect then go up on the main and put the clip back on the second groove and start over

before you start doing this make shure you run at least 2 tanks of gas mixed rich to make shure your rings are seated then go back to your mixture and then adjust.

[yzboyx]

Thanks for the tips guys, I'll drain the gas tomorrow and fill it back up with 20:1 Hopefully this will keep it from running too lean for now. I'll also try moving the clip down a notch. I'm just really worried because I have burned a hole through a piston before from running too lean after a rebuild. Less than 30 minutes on a brand new piston. I now know what an extremely lean running motor sounds like!!! The bike doesn't have that screaming sound to it, so I guess it's not too far off.

[Bryan Raffa]

no prob just rember that a fouled plug is cheeper to replace than a top end!!! good luck.

[MTS]

Thanks for the tips guys, I'll drain the gas tomorrow and fill it back up with 20:1 Hopefully this will keep it from running too lean for now. I'll also try moving the clip down a notch. I'm just really worried because I have burned a hole through a piston before from running too lean after a rebuild. Less than 30 minutes on a brand new piston. I now know what an extremely lean running motor sounds like!!! The bike doesn't have that screaming sound to it, so I guess it's not too far off.
Mixing it at 20:1 is a band-aid- and a POOR one at that, Buy the right Jets, Unless you Like doing top ends, As for sand......the redneck who had my Z before me ran it in sand with NO air filtre.......i bored it 2 size's from what it was and there where still scars below the intake.......:rolleyes:

[yzboyx]

I had one tiny scar that I couldn't see but I could just barely feel with my fingernail. It was very light and very short. Everyone I showed it to said, it should be fine. My jug is ported and polished and on the last bore, so I really wanted to reuse this one. I don't doubt you on the band aid thing, but why is it not a good idea? Doesn't it accomplish the same task as a different jet. I have no problems changing jets, I just want to know why I have to. Thanks very much for the info! I just want to learn as much as I can about jetting this thing properly. These damn pistons are expensive!

Thanks again guys!

[MTS]

I had one tiny scar that I couldn't see but I could just barely feel with my fingernail. It was very light and very short. Everyone I showed it to said, it should be fine. My jug is ported and polished and on the last bore, so I really wanted to reuse this one. I don't doubt you on the band aid thing, but why is it not a good idea? Doesn't it accomplish the same task as a different jet. I have no problems changing jets, I just want to know why I have to. Thanks very much for the info! I just want to learn as much as I can about jetting this thing properly. These damn pistons are expensive!

Thanks again guys!
Reading over the post's again, Let me say, Needle Postion and A/F screw Do NOT affect WOT, sounds to me you where Lean from the Get Go (maby why you burn so many pistons up before?), Now mixing your Gas and Jetting are 2 Diffrent things, The oil in the gas is for lubrication of the top end, Where as Mixing it a little richer Will Cause it to run a Little Cooler becuse More oil, Burns Less Intense(hard to explain what im thinking) Now jetting controls the Air/Fuel Flow into the motor, a Lean motor Has too much air Going though it, More air=HOT.....and vice versa..........Know what i mean vern?:beer

[Bryan Raffa]

what are you running for a main? stock carb?

[yzboyx]

I think I'm starting to finally understand! Thanks Mytrikesucks! Very good explanation! Bike ran great with this exact setup before. I sand blasted the original piston in this jug, but had many, many hours on it before the blasting! he he!! The only reason the other piston got burned was I used a smaller bore jug without rejetting. Don't know what I was thinking, just was exited to get her running again, forgot to do a chop!

I'm running the stock carb, but not sure exactly what jet size, because it was bubba'd out! By that I mean the ole "let's jus stick a drill bet thru er!" That's one reason I haven't tried changing jets yet. I'm not sure where to start.
Awsome info! You guy's rock!

[yzboyx]

This is assuming that a gray plug is a lean condition. I just read that it is normal for a plug to be light tan or gray in color. What the hell?

*However* this info came from a clymer manual.

[MTS]

I think I'm starting to finally understand! Thanks Mytrikesucks! Very good explanation! Bike ran great with this exact setup before. I sand blasted the original piston in this jug, but had many, many hours on it before the blasting! he he!! The only reason the other piston got burned was I used a smaller bore jug without rejetting. Don't know what I was thinking, just was exited to get her running again, forgot to do a chop!

I'm running the stock carb, but not sure exactly what jet size, because it was bubba'd out! By that I mean the ole "let's jus stick a drill bet thru er!" That's one reason I haven't tried changing jets yet. I'm not sure where to start.
Awsome info! You guy's rock!
How extinsive is your port job on it? if yu have the stock 32mm on it you may wana opt for a 36 or 38mm carb......Open it up a bit more...just snatch one off another 250, then at least the jetting is close and you can do chops and get it figued out from there. if you dont want to get a bigger carb, pop out your old jets and see what numbers are on there, you can then Assume to go Bigger.....on them....;)

[MTS]

This is assuming that a gray plug is a lean condition. I just read that it is normal for a plug to be light tan or gray in color. What the hell?

*However* this info came from a clymer manual.
Light-Dark tan is the colour you want, a Gray-white plug Is That colour becuse it burns hotter, burns more of the fuel and Is a More complete burn, Most 4 strokes are a gray-whiteish plugs............Anyways.....What kind of premix are you using too? some of them (such as Blue marble ) cause the plug to burn gray no matter what and make it somewhat of a Pain to jet accordingly by plug Chops....(which are not all THAT reliable in the first place, sice they dont use lead in the gas anymore......)

[Bryan Raffa]

lol!!! I got you now stock is a #470 the air screw 1 turn out pilot jet is a #45 And the clip on the second groove these are stock settings so you can start there checking whats in it.

[yzboyx]

It is a full drag port and polish. Head is milled, nationals pipe, and cobra silencer. Very extensive.

[yzboyx]

I'm using Mobil 1 full synthetic for premix.

[MTS]

It is a full drag port and polish. Head is milled, nationals pipe, and cobra silencer. Very extensive.
Hell...Throw that Stock carb in the Trash, Get a nice PWK 39mm......:beer it will be a whole nother animal....:w00t:

[Bryan Raffa]

hell ya throw that thing right in the garbage!! bigger carb then worrie about jeting it!!! could of saved on some typeing if we knew that lol!!

[yzboyx]

I'm sure there are better oil's out there, but I have like 6 cases of this stuff I got for free! I used yamalube before, with no problems. Could this also be a cause of a leaner running motor. I'm sorry forgot to mention I changed premix oil's. But the tank was probable 1/2 full of the yamalube gas if not more.

You really think I can go up that big in carb sizes? Quite a bit of a gain in performance huh? Is the carb you suggested aftermarket, or can I find one on another bike? I have access to a nice salvage lot.

[MTS]

I'm sure there are better oil's out there, but I have like 6 cases of this stuff I got for free! I used yamalube before, with no problems. Could this also be a cause of a leaner running motor. I'm sorry forgot to mention I changed premix oil's. But the tank was probable 1/2 full of the yamalube gas if not more.

You really think I can go up that big in carb sizes? Quite a bit of a gain in performance huh? Is the carb you suggested aftermarket, or can I find one on another bike? I have access to a nice salvage lot.
The 39mm Keien PWK is a Aftermarkt Set up- mine ran me 250$ CND i think, if you dont wana spend that kinda cash, you can hunt at the junkyard for an older Flatslide 38mm Off an 92-05 YZ,CR,RM, 250,.....will all work fine,,,,and are alot cheaper most of the time....But at the sacrifice of performance.....;) as for the Oil, i would just Run it, I have never used Mobile One so i dont know what its like, Yamalube is Bottem line performance but Gives good Protection....i run Amsoil or motoul and Like them both......

[yzboyx]

I've also used the yz250 head gasket to boost compression a little more, heard it was good for another 15 to 20 psi. Not sure yet, I'm going to run a compression test this weekend. Do I need to be running a higher octane fuel? I'm still running 87 in her.

[Bryan Raffa]

I'm sure there are better oil's out there, but I have like 6 cases of this stuff I got for free! I used yamalube before, with no problems. Could this also be a cause of a leaner running motor. I'm sorry forgot to mention I changed premix oil's. But the tank was probable 1/2 full of the yamalube gas if not more.

You really think I can go up that big in carb sizes? Quite a bit of a gain in performance huh? Is the carb you suggested aftermarket, or can I find one on another bike? I have access to a nice salvage lot.


I got a 38 on mine Ive seen 40s on them, no problem look for a 38-39 get one with the choke in the right tho i just burnt the crap out of my finger tonight trying to shut the choke off , its on the left right by the pipe!!! lol newer used will work fine, ebay if you got access, yz head gaskit does nothing, its same as a z

[MTS]

I've also used the yz250 head gasket to boost compression a little more, heard it was good for another 15 to 20 psi. Not sure yet, I'm going to run a compression test this weekend. Do I need to be running a higher octane fuel? I'm still running 87 in her.
Depends what kind of compression you have...over 200 PSI you need to run Some VP110 or c12 at at least 50/50 mix with 91 octane...

[Bryan Raffa]

run the best you can get. i run 112oc

[yzboyx]

Thanks guys so much for the help! I'll give ebay a scan real quick. What will the motor sound like if it needs higher octane?

[yzboyx]

Would a higher octane allow the motor to run cooler since it is retarding the fuel?

[MTS]

Thanks guys so much for the help! I'll give ebay a scan real quick. What will the motor sound like if it needs higher octane?
Very Pingy....Poping crackling on Decel....and Running VERY hot.......

[Bryan Raffa]

I wouldnt go by what it sounds like alone with your mods I would just run the best gas you can get.youll get pinging just like a car.

[Bryan Raffa]

is there a echo!!! lol

[MTS]

is there a echo!!! lol
I think just maby!!! :lol: It will run cooler with the proper Octane fuel in it,

[yzboyx]

Item number 4626430841 Is this what I'm looking for?

[MTS]

That looks like an old roundslide....i wouldnt bother with it....leme see what i can find on ebay for ya...

[Bryan Raffa]

that will work I personaly wouldnt use the twist you will have to re jet to your machine

[Bryan Raffa]

keep looking for a flat slide it will work though

[Bryan Raffa]

That looks like an old roundslide....i wouldnt bother with it....leme see what i can find on ebay for ya...


hook um up i gotta go to bed!:naughty:

[MTS]

http://cgi.ebay.com/ebaymotors/NEW-39MM-PWK-KEIHIN-CARBURETOR_W0QQitemZ4626572906QQcategoryZ43979QQtc ZphotoQQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Thats what you need right there......Not sure what kinda money You want to spend tho...

[yzboyx]

Awsome, I was just talking with a buddy of mine, and he just offered me 300 bucks for an old 200x I had! Looks like that bad boy carb is gonna be sittin on my Z. Thanks so much for everything! Everyone's been a great help. I'll keep ya posted on which one I put on her. I just can't imagine my Z being faster, I'll probably be glad I have the Westcoast +4 on it, and I was thinking about taking it off.

[BigGreenMachine]

You need to get some pics up of this Z man.

Anyone else thinking the change is oil brands is what is causing the plug colour to be grey?

[Bryan Raffa]

so did you find one?

[yzboyx]

Ya, I'm watching one on ebay right now, it's off a 2000 yz250. I'll post some pics of the bike in a few minutes, as soon as I resize them.

Thanks again for your help bryan.

[yzboyx]

Here's a couple pics of the beast!

The bike has also been changed to a six speed.

[yzboyx]

Well, I went out and moved the needle clip down one notch. The bike seems to run alot smoother. There's not quite as much pop in the exhaust sound. I also went one step cooler on the plug. Now the plug is a whiteish color. Is this good, or do I need to still go a little richer? I will still be putting a bigger carb on, but I want to ride now! I start vacation tomorrow and want to find the biggest mudhole I can throw her in.

[Bryan Raffa]

what plug are you running?b7es

[Bryan Raffa]

what size main is it? its stamped on the bottom of the jet if you spin the carb and take off the float boal nut look up in there with a flashlight you can see the # what grove are you on?

[yzboyx]

I'm using B8es. The needle is in the second grove from the bottom now. I don't think it would matter on the main jet, because it was drilled out unfortunately.

[Bryan Raffa]

b8es is a stock plug thats good, ouch on the main go all the way down with the clip and screw your air screw in all the way till its lightly seated and turn it back out 1 turn then check it. really cant do more than that with out changeing the main you want a light coffie color you might get away by screwing in the air screw a half turn if you really need to

[yzboyx]

I have a two stage uni air filter clamped onto the carb. What would happen if I were to put the stock air box back on with a K&N filter. I have it all setting right here. I know this would hurt my performance a little, but would the jetting be closer? Just a thought. I am a little worried about getting water in the carb with the uni.

[Bryan Raffa]

throw it on, you can do what i did with 1 inch uni vents, I added 6 more after the pictures were taken