YZ426 02 Problem i would like to share?

Hi Guys,

I have recently rebuilt my 426 from top to bottom & has been running great for the last 2 weeks! But when i took her out yesterday I came across a problem which i need some guidance with as in the source - fuel or electrical?

The bike started 1st kick I made my way down the road, About 1/4 mile it started to cough & splutter like it was running out of fuel? I came to a stop engine dead tried kicking her over a few times still nothing. Pushed the bike to a garage filled the tank with fuel & tried again to start the bike which I eventually did but had to hold the throttle slightly open & as soon as i shut the throttle the bike would cut out again. I pushed the bike home checked the plug looked ok a bit of carbon, did a spark test seems to be good too? So popped the plug back in & I must of kicked the bike over 50 or more times & nothing!!

So my question is...... Have i got a dirty carb or faulty electrics? Or maybe something else?

Any help in this matter will be greatly received! :)

If the spark is fat and blue and fires consistently, I suggest checking the fuel jets next, make sure they are fully clean with open holes. Wouldn't hurt to spray some carb cleaner through the passages too.

Hi thanks for your reply, I have cleaned the carb out today checked all the jets which were all good. Put the bike back together & tried to fire her up, about 30 kicks later she fired up & struggled to keep going & eventually cut out after 30 seconds! im struggling a bit now to figure out whats wrong? :) Any suggestions or advice from the experienced members of this forum would be much appreciated! :banana:

check valve timing.... Sounds like it may have jumped on you. just a thought.

I had a similar problem recently. The small wire from the coil had come lose from its socket. It was still making contact so the bike would start and run but when the revs increased the problems similar to those you describe arose.

You will find the wire just behind the exhaust.

Hi cheers for the tip I will def have a look at that wire! Well here is an update on the problem i have. I have cleaned the carb its like new now:thumbsup: I then proceeded to adjust the valve clearances (even though the engine has just been rebuilt by myself) They are now to the looser end of the tolerance so at least there is now room for them to tighten up. After all this work i felt confident in the bike starting..... But did it? did it f%&k. Anyway at least i have narrowed the problem down to the electrics! I did another spark test & there is nothing!! so i have checked all the connections & cleaned them for a detail inspection & all seem to be good:thumbsup: So i will now get a vault meter thing to check out the amps in all logical places. When i finally solve this problem i will update this thread just incase someone on here is experiencing the same problem?

If anyone else has had any sort of electrical problem like this please let me know your solutions:banana:


hey buddy i have a 2000 yzf 426 and I’m having the same problem. the kid I bought the bike from used it for ice racing, the bike ran fine for my 1st to trips up north in Michigan. my 2 trips consisted of about 6-8 hrs on bike in cold riding (snowing 33 degrees f)total then I rode it when it was hot out but I cleaned the air intake and it had problems stalling out then i got stuck on the trail and had to kick it over till I was dead then walked out like 4 miles because my bike wouldn’t fire. when I got the bike home I saw that the harness that went to the neutral switch was split the sky blue wire didn’t connect to anything could this be my problem and yours? I made all connections again but it didn’t matter this is where I’m stuck in your shoes. I tried to kick the bike back over new plug and all and 1st kick fires up no problem then if you gas it or start to push the choke in it dies out and sputters then it won’t kick back over , almost like its flooded. Then let it sit for say an hr and same thing 1st kick starts then dies…….. anyone have any clues I was thinking cams???????

I went camping a few years ago with my 426 in the high desert. I live and usually ride at sea level and when I first got there I thought my bike was running funny due to the elevation. So after a day of riding and a few beers I sat down by lantern light and tore the carb apart to move the clip on the jet needle. Anyhow blah blah blah long story short. There is a slide plate in the carb not really sure what it is called, but it can and will go in upside down. This is what I had done and the bike ran just like you stated in your original post. Went to the quads for the rest of the trip and took it apart when I got home and found the problem. Put it together correctly and everything was back to good and has been ever since.

Good luck!

You could disconnect your neutral safety switch from the harness at the CDI. That would eliminate that as a problem.

I removed mine altogether and installed a neutral switch cover.

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