ORIGINAL: Valve floater
I had the same thing with the plug last week. I went from the org. plug to the NGK cm-6 and had the gap at .020.
The plane ran good but it kicked my butt to start it. It was hard to start and i would flood it if i didn`t get it on the first 6 turns while hot. I may try another plug and gap it a tight .018 or .019? Or just put the org. plug back in.
I gaped mine .019-.02 . Have one gallon through it . Never a problem starting it . My buddy showed me how and it works great . When cold go full throttle with full choke . Flip it till it pops . Then turn off choke and go 2 clicks up from idle . Should start in a couple or few flips .
When the motors hot go 3-4 clicks up from idle . Flip it and if it starts cool , if it pops but doesn't start flip it 3-4 more times for kicks and giggles and then repeat cold start .