low rpm/idle knock
 

:confused: I'm just getting my 06 250 set up and the engine seems to be knocking while at it's lowest rpm/idle and at the very first crack of the throttle. It goes away if I pull the clutch in and it revs and rides great with one exception. This knock occurs while the engine is at idle on downhills or hard braking. It may just be the engine, but it does not sound right. I am going to change the tranny oil to Rotella today and try it again. I've had at least 10 seasoned riders (not mechanics) look at it and they are all dumbfounded. Comments range from "I've never heard one do that before." to "I don't know if it's an engine problem or a clutch problem." Any ideas fellas. Thanks in advance.

imo it sounds like a clutch prob. i have an unidentified noise with mine too. im pretty sure my clutch isnt adjusted right, and im switching to rotella this oil change to see if that helps
i actually jush went to get some, but its 419 at the local parts store and i only have 405 lol :)

Does it only happen when you're moving? If so it's the chain slapping the chain slider on the swingarm. It's un-nerving when you don't know what it is, but it does no harm.

+1 for what speedy said. I have found the newer chain sliders to be a bit quiter than the older ones but they still make some noise. Someone suggested gluing the slider down to the swingarm to limit noise but I have yet to try it.

Paul B

The knock is present when it is running and sitting in neutral. It is also present when it is being ridden as I crack the throttle or when I am decending a steep hill. I have the LTR chain guide and I am positive it is not the problem. My mechanic, who use to carry gasgas, said it sounds like a clutch problem too, Speedy.So last night I drained the oil, which looked pretty bad, and had a bunch of stuff on the drain plug magnet, and I took all the plates out of the clutch and inspected everything. No wear that was unusual and no cracks that I could see in the plates. These clutches are nearly bullet proof so I didn't expect to see the problem there. I'm hoping that it is not the crank going bad. Could that be a posibility. I am going to fill it with syn Rotella tonight, and see how it does. It also has a BR9ES plug in it. I have always ran 8's in my 250's, including my 03. Could this by chance effect low end idle? Thanks for your help guys. I have an enduro this weekend and I hope to get it figured out by then, or I'll have to give the 03 a go.

If all else checks out, possibly the dampers in the clutch basket, or loose rivits? VERY uncommon but that would add driveline lash and make noise when the load changes on/off throttle.

I'm not sure what the dampers in the clutch basket are or the rivits, but I'll have my mechanic check them. How could I rule out the crank as a problem Glenn?

I also forgot to mention, and this probably does not have anything to do with anything, but I was told my bike has an MC ignition. Could there be a problem with that causing it to not run right at low rpms since the MC ignition is more of a high strung igniton. Like I said, it runs great at all rpms except the lowest idle.

I just spoke to a guy who sells gasgas and husky locally and he said he just had one do the same thing I described. The owner tried everything and installed a Wisco piston and it still did nothing to correct the problem. He installed a Athena piston with less than 2 thousandths clearance of the cylinder wall and the problem was fixed. He said wisecos are forged and have more clearance due to swelling when hot (?) I may give this a try since the bike is on the original top end. Any thoughts?

Just an update. I'm still sorting out the source of the low rpm knock. I installed an Athena piston kit and all new gaskets and the problem persisits. I called a gasgas shop and they claim it is the clutch (which Glenn suggested also) so I took the basket out and there is play when you put the gear in the vise and try to spin the basket itself. Almost a half inch of play. They said something about rubber bushings or washers (which glenn may be referring to as dampers) that get chewed up in there. It looks like the rivots on the back of the basket would hold everything in place, but I guess not. Hopefully when I get my basket back from being rebuilt, this problem will be squashed. Its been about a month of chasing my tail to figure this out. :mad: Has anyone else had this problem with the newer bikes? My 03 has way more hrs and its fine.

i have a similar noise just as you get on the throttle even in nutrel someone here told me it could be pv tention or pipe rattle on the spigot mine has had it since new