Hi Rob and Bob
Sounds like an old radio show. But any way couple of diagnostic questions some of which you answered Bob.
- The vacuum advance is working - you confirmed that bob
- Is the centrifugal advance working, it should advance as you take the engine from idle to about 1000 rpm
- You say that the engine doesn't back fire but runs rough - have you checked to see if it is a particular cylinder
Like your method of checking for spark, I generally try to get somebody else to hold the plug wires.
The running rough once the engine starts reminds me a little of the starting problems I've had with my HUP when it has not run for a couple weeks, once it would catch it would run rough for several minutes before finally smoothing out it did this fairly consistently if the engine had not been run for about two weeks, never did find the cause. This is one of the reasons I plan to put the HUP engine on the test stand see if I can track down the cause.
Keep us posted on you progress
Cheers Phil