I've just rejetted my carbs and installed a new set of the NGK 7BES plugs. I'll be looking for some mixture information from them very soon. Having dealt with fouled plugs for too long I'm using the following protocol for starting and stopping the engine.
Open the Pingle petcock to the prime position for 20 or so seconds.
Raise the enricher lever ( make sure the friction adjustment is tight so the enricher will stay open. )
Pull clutch, touch starter. ( engine starts instantly, thankfully)
After riding I turn the petcock to the off position about a mile from home. Once home, I let it idle until the bowls are empty. (This is really important because I have no center stand and there has to be a reason why the #1 plug fouls first and worst.)
This seems to work for me.