Poor running XR400

[Bobby S]

I have a 2002 XR400 with a Baja Kit installed. The bike has been running perfectly until recently. The symptoms are missing, backfiring, running rough, won't idle, etc. I drained and replaced the fuel, checked and cleaned the jets in the carb and replaced the spark plug with no improvement.

I was wondering if this could be caused by one of the baja kit components, voltage regulator, battery, etc.

Any suggestions would be appreciated.

 

[XRpredator]

not to call someone out for lack of maintenance, but did you clean the air filter?

valve adjustment may also be in order. Sometimes just a couple tweaks on the air screw helps too.

 

[UFS207]

A friend of mine just bought a clean 1996 model XR400R about a month ago. Ran very similar to how you discribe once it was warmed up: backfiring, barely would idle, missing and all. Turns out the rubber intake manifold/boot that the carb "plugs" into was cracked almost in half on one side....the bike was sucking in so much extra air that the fuel mixture was going waaay lean.

Anyways, not sure if that is your problem but I`d check that first as it`s pretty easy to get at. If you see any cracks whatsoever I`d replace it; the part is about $50 unfortunately, but the bike will never run right unless it makes a perfect seal. My buddy managed to fix his with some fuel resistant liquid silicone while he waits for a new intake boot to be delivered. Bike ran perfectly after the fix.

Also make sure the air adjustment screw hasn`t worked it`s way loose and fallen out, I`ve seen that happen as well. Good luck.

 

[Bobby S]

Thanks, I'll check it out.