2001 XC 600 runs poorly

[Heypal]

I have a buddy that is having trouble with his 600 XC. Not exactly a mountain sled, but with the great wrenches that surf this sight I have to ask. There are 4300 miles on the machine. Currently the sled runs one one cylinder at idle. Evidently if he gets on the throttle it runs just fine. Just acts up in the lower RPM range. I took the carbs off last night and the seam clean as a whistle. Plugs are brand new and providing good spark. He took the reeds out and they also look good. We are stumped and looking for answers. Can anyone provide some items to check?

 

[Heypal]

Anybody?

 

[polarisboy]

did u take a look at the pilot jet? maybe its plugged...

 

[X2Freeride]

If your carbs are good like you say check your fuel pump and your spark.

 

[retiredpop]

I see this is a fairly old post and maybe you fixed your sled already. If not have you determined which side is not firing?

Is that side getting gas at idle? No gas could be a dirty pilot jet. Too much gas could indicate a choke not seating in the bore.

Have you recently had a belt failure that could have gotten into the crank seal behind the primary clutch? You could check that by spraying WD40 or similar substance onto the crank behind the clutch with the engine running. Any change in operation would indicate the seal is shot.

Have you checked engine compression with a gauge?