1987 250x runs great then dies. Every time, the timing is off. I reset it, but when turning the motor over after one full revolution the timing gear will be off 2 teeth, then 4 after the next rotation and so on. The cam chain is tight, but I can move the cam gear and chain without turning the crankshaft. If I turn the crankshaft the cam spins but does not keep correct time. What happened?

 

First make sure piston is TDC when setting timing. There are only a few reasons why this happens. 1st-piston wasnt @TDC. 2nd-chain is loose so it throws everything off, 3rd-cam gear is wrong size, 4th-chain tensioner is not working or bad. If you can turn the cam gear/chain with out the crank moving then I would guess either bad chain or bad tensioner. That shows loose chain.

 

Just took the cylinder off, when the tensioner broke last night it allowed the chain to come off the bottom gear. Both gears are good, put it back together and reset it, runs good now.

 

thats good news. On the plus side I bet you can now do all this with your eyes closed.