YZ426F Won't Wheelie

Hey Guys,

I have a YZ426F that I purchased a month ago. It had some issues with the carb when I bought it so I pulled it and changed the jetting from a 180 Main to a 168. Also changed the pilot from a 45 to a 42. Still I had issues with the carb and the bike was popping. Finally, I took it to the shop and they fixed it for a really good price. Bike runs great, sounds awesome, fair amount of power..BUT when I first bought it before touching the jets and taking it to the shop it would wheelie like crazy in several gears but it ran like shit..NOW I can feel it kinda float but definitely not popping up like it used to. Any ideas? Could it be the jetting?

Performance:

Dr D Full Exhaust

UNI

Location: Arizona

Elevation: 1200 Ft

Temp: 70 to 100 F

Thanks!

It could have someting to do with your jetting,remember these bikes are not made to wheelie.Because when you wheelie,you starve your bike of fuel by the fuel sloshing around.So I would take a look at your carb one more time to make sure you have everything right.

It could have someting to do with your jetting,remember these bikes are not made to wheelie.Because when you wheelie,you starve your bike of fuel by the fuel sloshing around.So I would take a look at your carb one more time to make sure you have everything right.

Hmm thats interesting because my bike is jetted properly and it still wheelies.

yeah thats shit because i could ride a wheelie from 1st thru 5th on mine and ride it forever and it always ran perfect

What did they do to fix the problem?

What did they do to fix the problem?

Replaced the bald rear tire ? :thumbsup:

Maybe its your technique and maybe you remember it wheelieing better than it really did. Other than that i couldnt see a valid explanation.

I agree on that one. Its like the people that ask how to get more power out of their 426s or 450s, when if you think about it, people that dont know what mods to do in the first place, dont even need all the power these bikes put out anyways- let alone trying to add more to them. :thumbsup: So changing your jetting shoudnt do that. Have you inspected the clutch?

Trust me this beast is not wheeling the same as it was before. When you flick the throttle in first that front tire should not be on the ground. Yes the rear tire is brand new. When it was in the shop the mechanic found a completely random part that was not supposed to be in the carb. (I bought this bike not running right) AND the fuel screw was missing the tension spring so it would move around when the bike was on not keeping the same mixture. Originally the bike would only run with the choke pulled out. Now the bike is running great but I'm just noticing less power. It's not a huge deal as you are saying, you dont ever need the power these things produce. I've noticed the fuel screw is backed way out..about 2.75 turns. One thing I've never looked at in the carb was the needle. I have no idea if it stock or where the clip is at..

The fuel screw isnt supposed to be that far out. Put the 45 in there that you took out earlier and you can turn the fuel screw in some.

My jetting specs are:

Model: 2000 YZ426F

Edit Revision Date:

Main Jet: 170

Pilot Jet: 45

Starter Jet: Stock

Leak Jet (if any): N/A

Fuel screw/Setting: 1.75 turns out

Needle/Position: Stock

Filter: Uni Dual Stage

Pipe/muffler: powerbomb w/ti powercore

Altitude Range:1100'

Temp Range: 70-80

Humidity Range: 30% -50%

Comments:

Boysen Quickshot is on there. Im not positive if the fuel screw is 1.75 turns out. Its normally right around there depending on the temperature outside.

You can look in the sticky for our bikes jetting and everyone has a different set up due to different conditions. Im not saying mine will work for you but its what Ive found to be best on my bike and it has more than enough power to throw my ass off the back in a heart beat

So what i would recommend is to put it back to stock jetting specs as a baseline, buy some jets that are a couple different sizes, and start putting them in. working on one circuit of the carb at a time, and get an adjustable fuel screw if you dont already have one. then see what direction it goes in, if it feels better or worse. Just like tuning suspension.

This thread is funny. I WISH I could get the front tire on my 426 to stick to the ground better!. hehehee

Good luck to the OP. Sounds like the jetting still isn't 100% right.

The fuel screw isnt supposed to be that far out. Put the 45 in there that you took out earlier and you can turn the fuel screw in some.

My jetting specs are:

Model: 2000 YZ426F

Edit Revision Date:

Main Jet: 170

Pilot Jet: 45

Starter Jet: Stock

Leak Jet (if any): N/A

Fuel screw/Setting: 1.75 turns out

Needle/Position: Stock

Filter: Uni Dual Stage

Pipe/muffler: powerbomb w/ti powercore

Altitude Range:1100'

Temp Range: 70-80

Humidity Range: 30% -50%

Comments:

Boysen Quickshot is on there. Im not positive if the fuel screw is 1.75 turns out. Its normally right around there depending on the temperature outside.

You can look in the sticky for our bikes jetting and everyone has a different set up due to different conditions. Im not saying mine will work for you but its what Ive found to be best on my bike and it has more than enough power to throw my ass off the back in a heart beat

So what i would recommend is to put it back to stock jetting specs as a baseline, buy some jets that are a couple different sizes, and start putting them in. working on one circuit of the carb at a time, and get an adjustable fuel screw if you dont already have one. then see what direction it goes in, if it feels better or worse. Just like tuning suspension.

Thanks for the input bro. The specs you have are the exact ones I was considering. I'm going to switch out my 42 for a 45 and take the 168 main to a 170. I picked up a dynojet kit for only 30 bucks so we'll see what it does. Also, I just got home from riding all weekend. I'm going to order a new clutch kit because it slips in and out of 5th gear when at full throttle..

It may not be the exact setup as mine but since you have a kit you cant just see what works and what doesnt. And my bike runs prime. Doesnt bog, starts first kick hot or cold. I actually think Ive only had to use the hot start button 3 times in the 7 years Ive owned the bike. So just look at the jetting sticky at the top of the 426/450 forum and you can get a more widespread idea of what jetting specs people are using for different locations.

Thanks for the input bro. The specs you have are the exact ones I was considering. I'm going to switch out my 42 for a 45 and take the 168 main to a 170. I picked up a dynojet kit for only 30 bucks so we'll see what it does. Also, I just got home from riding all weekend. I'm going to order a new clutch kit because it slips in and out of 5th gear when at full throttle..

Ok, the slipping in and out of gear is because the dogs are worn down on the gears, and they will need to be replaced. And do a search on the O ring mod, you will need it

Ok, the slipping in and out of gear is because the dogs are worn down on the gears, and they will need to be replaced. And do a search on the O ring mod, you will need it
True, that. 3rd and 5th on the main shaft, along with the shift fork. Clutch won't help.

So if I replace all 3 forks and the 3rd and 5th gear wheels I should be good? Sorry I'm fairly new to the transmission aspect of things.

No. The only fork that is related to this problem is the fork that slides the third pinion. The 3rd and 5th wheel gears (on the output shaft) are not involved, although you may find something wrong with them on inspection. The 3rd and 5th pinion gears (the gears on the main shaft) are the ones causing that problem.

That would be fork shift #2 correct?

Nevermind grayracer, I figured it out from one of your previous posts..thanks for your help, it's much appreciated!

Alright guys so here is what I have on order..

JETTING ISSUES:

Dynojet kit (Also looking into mods)

TRANSMISSION:

Yamaha GEAR, 5TH PINION (5JG5)

Yamaha GEAR, 3RD PINION (5JG5)

Yamaha FORK, SHIFT 2 (5JG5)

CLUTCH:

Entire Clutch Kit (Since I bought the bike used I figured I might aswell replace it)

Total: about $230

Before you start ordering parts, you need to get in there and see what's actually wrong with it. You need someone who knows what they are looking for to go over it with you. If your clutch is slipping, it is more noticable in the upper gears because there is more load on the bike. Are you sure the gears are popping out, or could the clutch just be letting go when your in the upper gears. You need to know before you start ordering parts. Could it be that you are going just a bit faster when you are trying to wheelie in first gear? 1st is so low, that you may just be running out of gear by the time that wheel wants to come up. Most use a taller gear like 2nd or 3rd to initiate a wheelie, even if started going really slow. Theres no way just slight jetting changes are preventing a 426 from wheelying. I can't believe I've allowed myself to get into a "wheelie" topic, can we go ahead and argue over the bikes top speed while we are at it?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now