Backfire under loads

[kazoocruiser]

I went back through the thread and didn't see that an oil change has been done.

You could pull the dip stick and see if the oil smells like gas.

I seem to recall that if the fuel pump develops a pinhole in the diaphragm, it can allow raw gas into the oil sump. There should be a small hole on the bottom of the pump you can look at to see if there is evidence of leakage, or wrap a rag around it and let the motor run for awhile, and take the rag off and smell for gas.

Diluted gas ruins oil sealing at the rings, and might account for your low compression readings.

ps, Thanks, geezer#99