02 YZ426F Problem?

I'm running out of ideas and need some help! Here's the low down... I installed the Hot Cams exhaust cam and installed a new piston/rings. The bike fired right up however, after it warms up it runs like crap, will stall and then not restart til cool. It almost acts like the choke is stuck open (runs very rich and fouls plugs). Ive made several attepts at leaning the pilot as well as the main circuts with no improvement. I have rechecked valve clearences several times. I even reinstalled the stock cam and it still does not run right. I'm convinced it is electrical as I yesterday I tried the "blue wire mod" and had some improvement? I did check the electrical components per the manual and everything appeared to be good. WHAT AM I MISSING HERE??? HELP!!!

I forgot to mention, the carb has been cleaned twice.

Okay, I ran it up and down the dirt road behind my house tonight. Ran good for a few minutes. Once it got hot it started loading up and running really rough... would not idle. I've been reading and searching this site for hours now and have seen several posts that talk about faulty CDI's. If anyone has any insight to this problem, I'd really appreciate it.

P.S. The bike will be for sale as soon as it is running correctly. This is due to the new 06 YZ450F parked next to it in the garage. :thumbsup:

I'm sorry I don't have an answer for you, but I do have an extra CDI box that I'll sell you pretty cheap if you want to try it. PM me if interested.

i had the same kinda problems everything tested good was able to borrow a cdi made no diffence,in the end it was a bad connection in the plug cap it comes apart from the plug end there is a resister and a spring in there each end of the spring was corroded causing a itermitant problem.

Thanks. I'll check out the plug wire/cap connection this afternoon. If that doesn't fix it, I'll get with Zique about that CDI. I really appreciate the insight as I have tried just about everything I could think of.

I also had a similar problem 01 426.I ended up finding a bad coil.I checked every electric componet and they all checked out fine bought a stick coil.Long story short coil was bad.Plug still really black but have not fouled a plug since.I'm now dropping my jetting to clean up plug hopefully.I feel your pain it took me about a month to figure it out.I was ready :thumbsup: the thing.

If your looking for a coil the Yamaha RX-1 - Apex snowmobiles coil works perfectly.Check out http://www.ty4stroke.com/viewforum.php?f=3 Always some body parting out a sled.If you can't find one in the classified put a post on the Rx-1 board that your looking for one.Don't for get to get the plug in conecter as well.

I have always had the occasional fouled plug problem, but now it won't even stay running once it's warmed up! Oh well, this little problem inspired me to buy the new bike, now I need to fix/sell the old one. Love the 450, but will miss the 426!!!

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