Bacfiring question ?

Last weekend was my first chance of riding my wr 426 for real :D. I mean real real :D. There was an organised tour by the local organisation of dirt rider :D. 280 dirt bikes riding along 240 quads. Nice weather but a lot of mud riding in the frehly melted snow :).

The bike was superb except for one thing . While riding (first gear plowing) in a knee deep mud section for a while :D (20 min or so), I felt the bike backfiring slightly a few times. As soon as I got the chance I stopped to cool me and the bike­ :D.

I assume that the backfiring was due to the overheating of the beast and/or a faulty jetting condition. :D

I'd like to have your suggestions on that. :D

The bike is stock except for the snorkel removed and a Unifilter in place. I normally have 0 problems. It stars normally first or second kick.

Once rested I resume riding and everything went fine.

If you want to see pictures of what is done here, the adress is next :


Sounds like your carb vent hoses ended up being submerged for too long. Are you sure it was backfiring and not popping or bogging down?

Only time my bike backfires is when I forget to turn the petcock from "off" to "on" after a break :). The lean condition this generates is the source (I assume) of the subsequent backfiring. I have no idea if this is related to your scenario (doubt it, but hey!), but I figured a bit of information is better than nothing.

Thanks for the reply. :)

I will re-route the carb vent hoses to the air box. This should take care of any plugging if this was the cause .

But to tell you the truth, I was so busy trying to keep going in that Knee deep sh*t , that you are right to question me about backfiring/bogging down/popping :D.

I was barely cracking the throttle in first and the engine seemed to want to kickback every now and then :D.

That's why I tought I was experiencing backirings. At one point I was concern of breaking or burning valves, but the misfunction didn't last long. And as I said, after a few minutes of cool down, everything seemed to be OK.

Your inputs are appreciated.

Thanks to all TT members


Hi Sylvain

Where did you guys do your ride,how far was it from the Ontaio border? I'm always looking for new places to ride.

Does your local club have a web page?

Hi Bam and Sylvain,

The ride was one of the FMSQ, probably near Montréal (St Michel des Saints ).

Hey Sylvain, I had backfiring problems when the engine was hot ( we talked about that already) and just wanted to mention that following my ride of the last week end, I can confirm that I got rid of the problem with a 175 main jet over the 165. The engine was sure very hot trying to follow my buddy's XR650R in open trails :). I know you mentioned the jeting is supposed to be OK but are you still running the stock 165mj?

All good suggestions. You may also check the valve clearance.

Hi Math !

I can tell you that this was a very great ride :) . Muddy but great.

To answer your question, yes I'm still running the stock jetting. And I'll get a 175 main jet and see how it turns out. Thanks for the tips :D.

One thing I forgot to mention, the elevation at which the ride took place is about 1500 feet. Do you think it could of had an ill effect on the jetting ? Made it leaner or richer ? :D

Should the dealer have this 175 mj in stock?

Did you install the main jet yourself ? I'll study the manual tonight to see the procedure.

Well done guys. :D With this feedback, it's much easier to fine tune our bikes.



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