Well I Pulled the head. All looked good and clean so I disassembled the intake valve and inspected the situation. The stem looks like a mirror with no ware on it or deposits. I can’t feel any resistance to the valve sliding through the guide and there is little or no wear in the guide. I polish all parties involved cleaned the dickens out of the head, guide and stem then put all back together with lots of lube. I set the clearances to both intake and exhaust.
I still have the same issue @#%!! The engine will start and run fine at slow speed (throttle 10% open) It is smooth and sounds good. If I open the throttle I get bang, bang, bang, from the carb. The report that emits from the carb is quite loud not hot, it is a popping issuance of gas not fire or exhaust. It is also noted that the engine has not sped-up to do this it just does it because the throttle has been opened and it does it on the first single revolution after the throttle is opened. It is not related to RPM.
A test I preformed was to start the engine with the valve cover off and while this back firing of the intake is going on I used a small pry bar the give a significant lift to the bottom of the intake valve spring , it made no difference at all to the sound of the engine as it continued to do what ever it is doing.
Is it possible that the ignition system is causing this like the plug is firing half way down the intake stroke? Also, though I have not seen it happen since this condition has worsened,, this issue origional would come and go. When this happened it required that I open the throttle at least half way and now it only takes a little throttle opening.
Any help would be great if you have any ideas, this could drive me crazy and I will have to take to drink and then the grass will over grow in the yard.
Thanks for your help already, Bruce