I would be looking at issues with carb. Needle arm setting "Should be OK" if it is holding pressure. At what pressure does it pop off? 10 -15 psi? Does it look like previous owner was in the carb? Put wrong fuel pump in or installed it wrong? Low mix needle in High mix port ( not sure if your carb will allow that).
Testing the jets and welch plugs are challenging my pay grade but IMHO there has to be a critter in there holding the flood gate open. Possibly a china carb to verify but for a few extra $ A new Walbro/Zama .
If your metering diaphragm is letting gas through (actuating the needle arm/needle) you have to be getting good impulse so a worn piston or rings or even seals would weaken the impulse which in turn would slow fuel flow not Flood the cylinder.
If you don't replace the piston I would entertain at least polishing it to minimize future aluminum transfer.
Some body with more savvy will hopefully pop in and have the "RIGHT" answer.
Testing the jets and welch plugs are challenging my pay grade but IMHO there has to be a critter in there holding the flood gate open. Possibly a china carb to verify but for a few extra $ A new Walbro/Zama .
If your metering diaphragm is letting gas through (actuating the needle arm/needle) you have to be getting good impulse so a worn piston or rings or even seals would weaken the impulse which in turn would slow fuel flow not Flood the cylinder.
If you don't replace the piston I would entertain at least polishing it to minimize future aluminum transfer.
Some body with more savvy will hopefully pop in and have the "RIGHT" answer.