I bought a 426 a few months ago, and love it when it will start. Some times it will start good and others it will foul a plug. I have done the blue wire mode and tried to richen the piolt next size up. Some times it still wont start. What should i do?


I feel like I've posted this message about 50 times. :)

My '01 started fouling plugs. It would run great all day, but the next weekend it wouldn't start without a new plug (everything on the motor is stock). To make a long story short, the fix for my bike was to change brands of gas. I switched from Mobil to Cheveron (now a Sunoco station) and the problem has been gone completely.

PS-> When mine was fouling plugs I found that I could clean them with carb cleaner and typically they would run fine after that.

it seems that all i read on these posts are how the 426 fouls plugs. i bought a 2002 back in jan. and i haven't had any problems with this. i think it has to be the rider[ the way the person is starting it ]. after reading about this i started to think that there was a flaw in this bike, but there cant be that many lemons out there. :):D

i think it has to be the rider[ the way the person is starting it ].

I don't think so. My '01 has been very dependable and I have been fairly sensitive to keeping it jetted right. But every once in a while it just decides to foul a plug - it's usually after a temperature change and I haven't adjusted the jetting. So, I always start my bike before I load it on the trailer (or the night before) to keep it honest. In 100 hours, I've had about 5 fouled plugs. I always keep a few on hand. Always starts on the first or second kick after that. At the track, I rarely kick it more than once.

I don't think these guys are doing things wrong, I just think the bikes are sensitive and need attention just like women!

i guess i will knock on wood, i hope it dosnt turn out like that. my bike is bone stock exept for new handelbars and clamp, i have not touched the engine. but i will say after reading all the posts about fouled plugs i do keep an extra one with me now. :D:D:)


First make sure everything is right

Air filter not over oiled, no air filter oil or dirt in air jets, fuel screw adjusted right

My 00YZ426 still has the orignal plug

but when it was new I would stall the bike and it would take 20 - 30 kicks to restart (flooded)

then I did the BK Mod and changed the Accelator Pump Spray from 5-6 seconds to 1/2 second

Then when I stalled it 1 or 2 kicks to restart

My point is all that accelator pump fuel can be helping to foul the plug, it might be worth checking

FYI Also went to Steahly 14oz. Flywheel and quit stalling the bike (at my age I would rather ride then Kick)


My buddy and I both have '01 426F's. I have had no such problem while he was fouling plugs from the get go. We both did the BK mod and he has not had this problem since. My bike just runs awesome as it always did. One thing to note is that both of had longer duration accelerator pump sprays than the reccomended 0.35 sec. I went from about 2.5 sec and Jeff went from about 3.5 sec. Like I said, both bikes run awesome, its just the rider now. You can get a good rundown on this mod off motoman393's website. Hope this helps.

Those are my thoughts......


Try these things to help. It sounds like your rich in the pilot circuit and/or some how your getting fuel into the motor pre-maturely.

When starting:

Don't prime the bike. Turn the fuel on, choke on, Right hand on the brake master (not on throttle) find TDC, move kicker one inch and back to the top. Now kick like a one-legged mule. Put the old pilot back in.

When you stop riding for the day:

Turn the fuel off and let the bike run until it uses all the fuel in the bowl (dies on it's own).

let's us know if this makes any difference.



Rich causes carbon fouling. Going richer on the pilot would make it worse.

If this started out of the blue, my suggestion would be to clean the pilot jet. They are frequently plugged and oddly make the pilot richer instead of what you would think. It seems filter oil is always the source of plugging.

Next suggestion is to jet bike top to bottom. It could be fouling from needle or main too rich.

The blue wire is a maybe. I can't personally vouch for it because mine doesn't need it.

Don't ignore the fuel types. Try different brands if nothing else works.

Good luck,


my bike fouled plugs like hell, it was brand new, the dealer dropped the needle, adjusted the floats, turned out the air fuel screw, and I did the blue wire mod. Now I am not fouling plugs as often ( I only have a couple hours on the plug though)

mike,i guess you finally got bike to start.

hey war, shouldn't of done that buddy! thats what i said after 2 months of owning my '01 i was happy it wasnt a plug fouler. then BAM! 3 plugs in 4 weeks. :)

I have a 426 and have never once had any problem with fouling the spark plug. Ha Ha

Thanks for all the ideas! I went riding today and it started just fine i adjusted the bk mod screw so that might have helped it. Also it seems to me that the decopress lever is trying to stick that could be why it would not start.

thanks again

Youd know if the decomp. was haning open, you wouldnt have anything to kick against.

Id recomend, before you kick yourself into a coma, get some race fuel and ride your bike on that for a tank. Just to see. I bet your starting and fouling issues magically disappear. Try any kind of race gas, Trick is fine, VP red will work fine, although C-12 seems to most available. The high octane isnt the goal with the race fuel, correct formulation is. Your bike may not "need" high octane fuel, but it doesnt need all the oxygentates and ethanols that "pollute" pump gas either. Most people dont realize that pump gas now is formulated to NOT evaporate. The MTBE thats in it prevents it from atomizing in carburerated applications, as opposed to fuel injected ones, where the fuel is mechanically atomized.

Shawn, sometimes i would not have anything to kick i could push the kick lever down numurous times without pulling in the lever.

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