B

1000yds · Jul 28, 2011

What would be the valve "lift" of the cam in a 39 B? Just trying to determine if the cam is worn enough to replace. Keep getting a puff back through the carb once in awhile and it runs rough. New springs,valves,carb AND mag. Just about out of things to try. HELP!

Kurt_JDB · Jul 28, 2011

Are you pretty certain you have it timed correctly?

Kurt

1000yds · Jul 28, 2011

Well I THINK so. I agree it would seem not to be though. Everyone seems to have their own technique. What's the foolproof way? 4 valves and two cylinders, you wouldn't think it would be rocket science.

BushogPapa · Jul 28, 2011

Have you checked the inside of the Mag cap for Moisture or Carbon-Tracking..?

Both can and WILL cause what you describe...to the point they will NOT run..

You do know that these early JD's do run somewhat erratic by Nature..

Ron..

gtx1967jewison · Jul 29, 2011

its the carb.

B

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