Originally Posted by TNC

#4--I took from your first question that you already have a good, serviceable 331 kit. If so, it wouldn't be worth what is likely an imperceptible difference between a good 331 kit and a 351 kit. If you don't actually already possess a 331 kit, well, I'd probably go 351.

#5--I think I'd pass on using that carb unless you get some really clear direction from Yosh on how to jet it for the KLX...and the jets to do the job.

#6--Yes, sounds like the cam chain guides. That's not a common failure in such a catastrophic manner. You're going to have to break that engine down to splitting the cases IMO to insure what you're dealing with. The crank may need some professional inspection.

#7--The KLX drivetrain and cooling system are more than adequate to handle any big bore kit we've dealt with here. If abused, the clutch might be weakest link but not to any concerning degree.

Clarification: I'm taking it that the 300 head you have is complete and in good order, and the head that had valve/piston contact is the original 250 head???

Originally Posted by GBAUTO

Guaranteed that the engine was run low on oil-although the bottom end and trans use ball bearings I would look for another motor to rebuild. I can tell you from experience that it doesn't take much to get a rod knock. Any pics of the carb?