We fitted new mains bearings in my mates Gas Gas pro 250 as he said it was knocking, he has just finished rebuilding it and started it for the first time-but he says it is still knocking! I have not been to see it yet but what else could it be? Little end bearings were ok, we checked for any up and down play there. Could it be piston/rings? Help please we just want to get out on bikes again.

check the teeth for ware and tear on the kickstart idle gear. if its knocking as you rev engine and goes faster and slower with the rev fluctuations it could well be that.

Does the rattle go when you pull the clutch in???

Benz

Hi this may be a completely unrelated topic to your problem my 2005 Gas Gas txt pro had a knock and i showed it to my friend who has 15 years in the motorcycle trade and he said it needed new piston and rings. I bought a S3 piston kit from trialenduro.com on line and bingo problem solved i think the kit was about 90ish quid plus p and p.

check the teeth for ware and tear on the kickstart idle gear. if its knocking as you rev engine and goes faster and slower with the rev fluctuations it could well be that.

More of a rumble than a knock,maybe?

yes but its down to peoples perception of a knock chap!.

yes but its down to peoples perception of a knock chap!.

More of a unga,unga than a dukka,dukka?

More of a rumble than a knock,maybe?

No, it sounds like a knock even if the damage is vey slight to a tooth. Easily and cheaply resolved.

Update on Knocking Pro, we had a good listen to bike and knocking noise seems to be coming from clutch area, also noise changes when the clutch is pulled in-but knocking noise still slightly evident. When we tipped bike on its side and took off side casing we noticed that we could lift basket of cluch up and down 9may be 0.3mm movement) even though centre screw was tight. Should this movement be there and if not how can it be repaired.