I took the wr426 out yesterday and the thing was running like hell. i had dropped the main one size because i was heading to the high country but did not go. I took the bike out for a ride,not thinking one size would make a diff.. It was popping and backfiring like crazy.I put the other main jet in and it still was back firing. Ichecked the plug and it was a sooooty black color.I am not sure what would cause this?

I am not sure but I know my bike will carry on for about an hour if I dont warm it up for about 5 mins.

I just remembered that i had just changed air filter,I read in dirtbike magazine a while back something about when you have freshly oiled your filter it can suck oil into a tiny orifice in the carb and not run properly unless you take carb out and clean with carb cleaner....Any help would be appreciated...

usually when the bike starts to backfire or pop on the run down it is caused by the pilot jet being blocked or two small. But as for the air filter oil causing it, it would only do so if you saturated the filter!

But with saying that im a bike mechanic and riden bikes for over 12 years and to the best of my knowledge ive never had that problem caused by the filter oil. You may have a bad batch of fuel or have you changed the brand of fuel you use?

ColoradoJim, it sounds like you need to check your air/fuel screw. The plug symptom is that the bike is running too rich. Leave the main where it is & lean or back out the air/fuel screw first to 1/8, if no change, then to 1/4 turn out. Try that.

If this has no effect find out what the correct jetting spec. for your altitude is & change to this(but set air/fuel screw to original position - you can get rid of the backfire/popping by leaning out the air/fuel screw, as described above). also, a freshly oiled air filter that has not set for at least 2-4hrs will make your bike run richer. Also do not saturate the filter with oil - squeeze out the excess.(I always have a extra air filter that is oiled, stored in a ziplock bag)Hope this helps

This might be a dumb question but is your hot start knob pulled out? This would cause your bike to backfire badly.

[This message has been edited by Jason Williams (edited 06-28-2001).]

Good point jason! My bike had a remote kit on it when I got it and after the gray wire mod the bike was stalling when I turned hard right. I looked the bike over and the cable was routed under the tank bolt but was to sort and had to be routed over the tank bolt. Every time I pulled the bars hard right the cable pulled and the bike sputtered or stalled. It sucked cause I was doing a dougnut turn around from a stop and it shut off and I fell right down in front of a bunch of people. :) Somethings wrong with my bike I said! Sure, Sure, have another cold one buddy! Dooohh! heheheh.

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