I had a chain come off on my XT500 and break the left hand engine case.
I got a new case and rebuilt the motor, when I started it, it had a knock.
I could feel a knock through the crank so figured it was main bearings
I pulled the motor out replaced the mains, re-fit run and the knock is still there!
Ok it’s the big end
I pulled the motor out replaced the rod, bearing and pin, re-fit run and the knock is still there!
Pulled it put again! Stripped it and checked the endfloat on the crank and replaced the clutch shaft bearing
Re-fit and hang on, the bike won’t move.
I pulled the motor out and found I had put a selector fork in BESIDE the groove on the gear which jammed it in two gears at once
Re-fit, run and the knock is still there!
By this time two of us were getting the motor out and on the bench in 12 minutes. I was removing the entire clutch to cut down on the weight. Each of us did the same job each time.
This time I started very slowly, I removed the motor complete and put it on the bench.
Removed the plug and turned it over, it had a knock.
Removed the tappet cover and cam, it had a knock
Removed the head, it had a knock
Removed the cylinder and piston, it had a knock
Removed the side cover and clutch, it had NO knock!
When I checked the primary drive gears I found a mark on the clutch drive gear.
Every time the motor turned about 2.5 turns it went clunk!
I was a bit peeved but happy at the same time.
Re-fit, run and no knock!