Unidentified engine/gearbox noise

[PBWR450]

I finally had a chance this weekend to air out the 01 EC250 I bought last fall. Recent maintenance includes a cylinder replate to A specs with a Vertex piston, bottom con rod side to side clearance was within spec and there appeared to be no up/down play. Clutch has recently started to rattle some at idle, possibly dampers because it goes away when clutch lever pulled in.

Anyway, while at a poker run this weekend part of the course was a good clear uphill section. While climbing this section in 4th gear about 1/2 throttle I began to hear a squeling almost grinding type noise that appeared to be coming from the right side. It immediately went away after dropping the revs. I ran the section again in 3rd gear at the same RPM range and did not hear any noise. I then tried it again in 4th and the noise came back at about the same RPM range as before. Anyone have a clue what may be causing this?

 

[jostby]

Are you sure the clutch isn't starting to slip a little and is growling? Mine will make quite a chatter/growl when I get it real hot. If your clutch is about done it could be the cause. A bad clutch will often start slipping in the higher gears while under load and isn't always very noticeable. Good luck.

 

[PBWR450]

Thanks for the quick reply jostby. My initial thought was the clutch slipping but frankly, I never had a dirt bike long enough to wear out a clutch so have never heard one slip . Growling is a good description of the sound it made. Thanks again.

 

[jostby]

I should clarify, I have not had to replace my clutch. This happens when I don't change the oil as I should (and then abuse it). You might check and make sure the level is good or try doing a oil change before condemning the clutch.