Engine Knock at high rpm

[jd250r]

Went out riding this past weekend and notice my engine started to make a knocking noise, but only at high rpms. Seems to still have good power. Any ideas on what it might be? Thanks in advance.

[bwamos]

Is it loosing power at the same time? Is it more ping or a deeper knock?

If your pinging (not your standard 2-stroke ping of course).. your most likley running lean on the jets.

Try turning you choke on 1/4 of the way and see if it runs any better. If it does you need a bigger main jet.

[jd250r]

It doesnt seem to losing any power. Its a knock, not a ping. Would it make a noise when the counterbalance bearing goes out?

[Quadude32]

A word of the wise trust me they always run great just before they BLOW UP:eek2: I had a counter balancer bearing go outon me and it took out both case halves cracked it right wear the bearing was and some of the bearings went to the otherside inwhich it scared and F*ckup that half too....Best bet would be pull the counter balancer out and see if there is any extra play in the bearing........Knocking i take it is coming from the front of the motor ? You could be starting to get a crank bearing going out.....There is a ton of things trust me i ve had them all happen to me i ve raced the R for 15 yrs now.

[MR.BIG]

Your rod bearings or crank bearings are on the way out. Fix it now or it might take something else out.

[jgracing]

i know what your problem is.... you need to be running a higher octane gas

I have this problem at the MX track after they till it, when there is drag on the back tires and your pushing the bike, it needs to have some good quality gas to keep the engine crisp

[jd250r]

I've ran the same gas/oil (brand) mixture now for 3 years and never had this problem. I think its down to the rod or crank bearings.