2001 426 Electrical or Fuel Issue

They will idle more or less normally sometimes, and be OK above 1/2 or 3/4 throttle, but in between they will be very rich.

hi . my 01 wr 426 has a 1/4 to half throt pop too, driving me nuts !! i also lost voltage out put from stator.pulled stator talked to B.D. checked stator ,ohmed out .7.so figured good .reinstalled no out put.bike seems to pop more than before, did you find your prob yet?

Well I am back with more questions!!! :busted:

I replaced a lot of carb parts last spring, along with the boots going to the airbox and engine. I took the bike back to the mechanic in April and he got it running OK, but there was still some popping on acceleration. Later this summer I installed a WR400 stator, flywheel, CDI, and wiring harness and had ridden the bike six or seven times with this setup without issue. I rode the bike all summer and lived with the slight problems, then we ran into big problems.

October 20th I went to the White Knuckle hare scrambles (where WIZ636 ate the engine on his 06) and rode the night poker run in preparation for the 24 Hour at Goldendale the following week. At the end of lap two I got into a deep (5 foot) silt rut and had to hammer the throttle getting out. Once I was out the bike would hardly run. I had to limp back on the hot start to the pits about 2 miles away. I shut the bike down and called it good.

The next week I cleaned out the air filter and carb and still had the popping on accel issues. Thinking I may have had an exhaust leak I borrowed a buddy's pipe and headed out to the 24 hour race in Goldendale. I rode the first lap and had nothing from zero to half throttle, then the bike ran like a raped ape. I brought the bike in and we went through the carb again, but everything appeared great. My buddy took the bike out on a night lap wanting to test out the 8 inch HID and ran into the same issues. Upon Mike's return we took off his carb and put it on my bike, nothing! I have also tried a different coil with no results.

So, two weeks ago I took the bike up to the Yamaha mechanic and had him give it another look. He pulled the head and found the center intake valve severely tuliped (and tight) and another intake starting to tulip. His solution to my problems is to replace all of the valves which he stated would be $700 with labor and the Ti valves.

Last week I ordered 2000 SS valves, springs etc., piston and rings, cam chain, and a hot cams auto decomp exhaust cam and will be spending $700 on the rebuild including labor.

My question: Is this really the problem that I am experiencing? I should have asked this question 2 weeks ago :banghead: The bike is definitely due for a rebuild, but I am gonna be severely depressed if this isn't the issue.

What else is left?

I forgot to mention that the bike was backfiring severely and shooting big fire balls on acceleration and deceleration. The bike felt like it was running lean, but smelled very rich. I was also having a difficult time starting cold and going through a lot of sparkplugs as of late.

replacing the coil and carb didn't move the problem. What's left is the the stator, CDI and harness. I'm assuming these were used components, but even if not, the problem was gone and is now back, so you have to start troubleshooting your current problem, not your last one, as if it were completely new. Start by checking all the grounds and connections, if the bike acts up when it goes back together.

And yes, a badly worn and tight intake can do what you're talking about here, so don't worry over it until after you get it back together.

YES!!! This will fix it... Yamaha does NOT have issues with CDI stators or coils for that matter.. You will be a happy Man when they're done!! Let us know... Good Luck!!!!

I forgot to mention that the bike was backfiring severely and shooting big fire balls on acceleration and deceleration.

Is that what all that flashing was at the 24 hour race? I thought a UFO was doing a fly-by. :banghead:

Hope your problem is solved with the top end rebuild!

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