Bike will not start or run right.

I have a 01 YZ426 and i just pulled it out of the garage the other day. it was about 40 degrees outside. for one thing, the bike will never start inside a warm garage unless you kick it over about 20 times. Today when i got it out i pulled the choke out, and i didn't touch the fired up after 10 kicks or so and sat and spit and sputtered until it just wouldn't run anymore and it died and it would not start again. I pulled the plug out and it was black and sutty. I've read on how the CDI's have been going bad on them. could this be my problem or am i doing something wrong cause i am really getting fed up with the bike the way it is running. it will be fun once i get it going but until then someone please help.

thanks so much.


Pete- if you haven't yet, try changing the plug. I've spent alot of time working on bikes with some kind of problem and ended up solving the whole problem by changing the plug. If this doesn't do it post back and some of the guru's around here should be able to fix you up...


I purchased a 01' 426 that would act the same way. After three rides on the same plug it would sputter and not run well. I would change the plug and it was like a new bike. Went to the dealer where I got it and He replaced the CDI with a new bike he was assembling, no change. Then he replaced the mapping circut in the carb. This solved the plug problem, but the bike didnt feel as good as it did with a new plug, so he is replacing the carb to fix the soot on the plug. Hope your dealer is as good as mine!

Start with a fresh plug - then be very careful not to apply quick bursts of throttle until the bike is fully warmed up (let idle for at least 2 minutes, then only apply throttle slowly). When you blip the throttle you shoot straight gas into the engine, which when the engine is cold is more than the plug can handle. The natural reaction when a bike starts to miss is to blip the throttle to warm it up, but this actually makes it worse with these pumper carbs! I have not fouled a plug in 2 years on my 98 WR400 since I started paying careful attention to that. Have a stack of about 10 plugs before I figured it out. I also switched to a CR7E plug (hotter) but not sure about that for a 426?



98 WR400F, YZ'd cam, YZ muffler

I just fouled my thrid plug this same way. I rode it a couple of times, then I started it in my garage and it ran for a 30 seconds then died plug fouled.

The bliping the throttle makes sence. If it is not warm it will be getting a alot of fuel while cold.

I have a hard time believing the CDI is bad. It could have bad mapping, but then all the 01 should have the same problem.

I do like the idea of the CR7E plug. I am going to try and find some.



01 YZ426F #85 Vet C

One more thing - I see you mentioned 40 degree weather - when it is that cold I usually cover one radiator with a piece of cardboard. There is no thermostat so the whole engine (and the plug) run too cold in cold weather (in my opinion). I have not had any overheating trouble, but only do this when the temps are around 50 or lower. One more thing to try .... Hope you have some luck I know I am waaay hapier with my bike after fixing the fouling thing. Very frustrating at first - I am very good at removing the seat/tank though!



98 WR400F, YZ'd cam, YZ muffler

Pete: I hope you aren't leaving the choke on for an extended period. About 20 seconds should be the maximum...and less as the ambient temperature rises. I doubt that I've ever left my choke on for more than 10 seconds...even when it was in the low 30's out.

[This message has been edited by Boit (edited 03-15-2001).]

Good comments by everyone.

Be sure to use a slightly faster idle too. This will allow turning off the choke early ( less than 20 seconds) and helps avoid the need to twist the throttle to keep it running.

How many turns out is the pilot screw?


I think I may have killed the last plug leaving the choke on too long. Since, I fouled the second plug, I have been letting it run longer with the choke on to get it too warm up and not die.

I will turn the idle up a tad and use less choke.




01 YZ426F #85 Vet C

[This message has been edited by forloop (edited 03-15-2001).]


best thing to do is leave the bike with me for a few months and I will sort things out for you. I may even be able to diagnose a bad midvalve in the forks........

Thanks for the help everybody. I picked up some plugs today and i will see tomorrow if i can't keep the thing running. I really hope i do not have to get the carb replaced like a lot of people are talking. When you guys first start the bike up do you usually pull the choke out and that's it or do you give the throttle a few turns? just curious on that. Thanks again.


P.S. DhLaw- i'll keep that in mind :)


This routine has worked for me since I have had my 98 YZ400. It works on my 01 too.

1. turn gas on

2. pull choke out all the way

3. using comp. rel., kick through 3-5 times

4. kick to start

5. leave choke on for no more than 10-15 secs

6. shut off choke and let warm up (may need

to turn idle up a bit)

7. go ride!!

This starting routine was given to me by a pro who has raced 4-strokes for many years. I have used this technique since I got my 98 YZ400 at the end of 97. I have never had a problem starting the bike this way (either one).


Something just occured to me that was told to me by my riding buddy. He said he has noticed that if he closes the petcock at the end of a ride and let the engine run about 20 seconds or so before shutting it off, that his bike starts much easier the next time. I have ALWAYS done this with my 426 and my bike starts easily no matter what the temperature is outside. I only do this to prevent fuel from dripping out of the carb float vent line while being transported in my truck. Coincidence? I can't imagine how any excess fuel could possibly slosh pass the pilot jet and into the engine during transport...and even if it could, it would be such a miniscule amount as to be inconsequential. Maybe there is something else going on by leaving the float bowl full?¿

[This message has been edited by Boit (edited 03-16-2001).]

Thanks yzernie, i used your suggestions and after i put a new plug in it the thing runs AWESOME. i think i've the the procedure down now. This thing is very fun. thanks for all your guy's help.


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