426 jetting

8 replies to this topic
  • MountainManic

Posted June 07, 2004 - 12:33 PM


My 426 is fouling plugs as often as twice to five times a month, usually just after sitting for a week till I can ride on the weekend. I have the full system fmf Ti 4 exhaust and an external air/fuel adjustment screw and no matter how I adjust it, it still fowls plugs and its getting old. Should I get it rejetted? Any suggestions welcome. Thanks

  • roktoy

Posted June 07, 2004 - 01:01 PM


Can't get you pic link to work.....

  • Fastest1

Posted June 07, 2004 - 05:02 PM


First of all always turn the fuel off at the end of a ride and let it burn up the fuel til it dies. I would suspect a high float level since it seems to do it after sitting. Maybe too big of a pilot also. :thumbsup:

  • ltrosson

Posted June 08, 2004 - 09:36 AM


You may think this is stupid. My 426 fouled plugs everytime I rode it. I changed air filters ( twin air ) and it not not foul another plug until I put the stock filter back on, I did that because it was clean and it was race time. AS soon as I tried to start it, it fouled the plug. The stock filter is in the trash and no more problems. I was told it had to do with air flow.

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  • RJB

Posted June 08, 2004 - 11:34 AM


How long does the bike normally run with the fuel turned off? Mine seems to go on forever.

  • MountainManic

Posted June 08, 2004 - 02:20 PM


fix pic link, thanks for letting me know!

  • Fastest1

Posted June 08, 2004 - 03:15 PM


1 minute or so, maybe a little longer.

  • Razman27

Posted June 09, 2004 - 06:45 AM


I had the same problem for a long time and would foul plugs non-stop. I read all the posts about air filters etc. They all had some positive effect, but non like what I finally did last. I took a few hours aside from riding to remove the carb to do a complete cleaning. If you've never done this, read a few posts about it and you'll be a master. I put it all back togther with the stock settings and jettings. Then I implemented a storage procedure I came accross on an old post a long time ago. It is as follows. When I come off the track or finish trail riding, I turn the gas off on my way back to the pits. I take a few turns in the pits and goose it a few times to get the gas burned out. If it is still running, I just let it idle there until it stalls. Then I push on the kick starter until it wont move anymore. It is the point where on my 01 426 you'd have to hit the decompression lever. What this does I guess is keeps it at top dead center and prevents fuel from migrating into the engine compartment. I swear on my mother's life, I did this a year and a half ago and have not changed a plug since. I was so frustrated because I would have to change a plug before every ride.

I hope this helps, but one negative result of this fix is - I don't clean my air filter after every ride like I used to. Shame!!!! - Shame!!!!

  • Matt96xr6

Posted June 09, 2004 - 05:05 PM


Check your AC pump timing.

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