man that sounds real familiar.....before i ripped mine completely apart I had the nearly exact same symptoms as you are experiencing....dejavu or what......It was a mystery that I could not solve, My carb was getting fuel, but I noticed that my spark was weak, and sometimes non existant.....the only conclusion that made sense was the coil had crapped out at the end but from sitting for a while the wires looked corroded at the plug ends and maybe the wires were also shot, I just turfed them. I ended up in the end to just completely rip into the motor and make it race ready....I never did resolve that issue, but your problem is the same as I was having......if you are running the hei, might be the coil and or the wires. When I park mine for the winter I noe remove the wires and the cap and rotor and put it in the house to keep the moisture away from it......When you find the culprit please let us know...thanks