Rick ,
I have to agreed that the limited running issue is carb related . The fuel in the crankcase was not known at the beginning and the quitting after getting hot is characteristic of a bad coil . Through all this , I think I've singled out the best components that I currently have .
And , I think you may be right about the seats being messed up .
I haven't tried the four hole meter tube yet , which I think will , at least , lessen the amount of fuel in the crankcase . There was less after I soldered the holes that I drilled in the tube . So ...
Then there's always the Carpenter carb .
I've thought about a better seal at the rotary valve port in the crank . I think a better seal there would help . Something I'll have to work on . Is the crank diameter at the port the same as the inside diameter of the main bearing ? It seemed pretty close , if I remember right .