KLR engine knock

[monchopper]

Just replaced the barrel and piston on a mates '86 KLR600.
The bike fired first time, ran sweetly for about 30 seconds then it started knocking.
Took off the cover and the timing now seems to be out.
Cam chain seems to have slipped on the crank.
Pulling apart tomorrow.

Any ideas of cause ie cam chain tensioner not working properly.

Sorry for the vague description, but someone might have had a similar experience and can share some wisdom!!

cheers

[Crisis management]

I don't know that particular motor but if the camchain jumps a tooth that is usually indicative of a worn chain and tensioner / slider. Replace both.
Check what the "knock" noise was....if it was valves hitting the piston you may have bent valves, pull the head off and check for any marks on the piston crown or other evidence of damage.