OP, klx678 isn't just trying to steer you to buying his tensioner. This is a common failure point on the KLX in all years. Your bike may indeed have some other problem, but the OEM tensioner is a weak link. I agree with klx678 on the mechanic's response...unless there's some issue in the bottom end that allows the crank to have lateral play and affect the tensioner crank sprocket. But if that's the case, you have some serious problems there.

I'm curious about your comment/question about the valve adjustment. If you don't have a manual and have never adjusted valves like these, you need to do some research. Maybe I misunderstood that part about your valve adjustment. You need a manual to check clearance values and the instructions on how to pull the cams and put the correct shims in there for proper clearance. There are torque values you'll need from the manual too.

 

im goint to check the valve clearance if anyone knows how to set torque on this wrench ?

 

If you do not know how to use that type of torque wrench you should pay to have your valves done. You seem to be not quite on par to do so.

Otherwise I'm thinking you're yanking our chains, trolling us a bit.