Scooterotica

It's your coil I've had the same thing when it warms up it starts to break down.

Could it be the wrong heat range plug? Just guessing as you mentioned it was previously eating plugs?

i had an issue with my varitronic kit as was frying plugs, did 6 in a 40mile round trip. i tried differnt brands of plug and grades. in the end i think it was a plug cap, one of them soft rubber ones changed to a ngk bakerlite type which when fitted you could feel it click over the thread on the end of the plug. worth a try and a cheap try.

I've had a similar problem whereas on a long run the ignition seems to hold back as if too far retarded around 3.5 to 4.5k revs and I have to wait for the revs to climb out of this rev range then it revs out to max. I bought a new stator after trying other CDI s(still the same) but after being fine for a while it started doing the same.One day I will f@@k it off and buy something better like the motorcycle conversions.

Having spent days replacing ignition systems on scoots over numerous IOW weekends, the most reliable set-up appears to be a BGM stator with an Indian flywheel, and Ducati CDI's and Regs. Can you borrow what you need to try this?
Of course, Im not saying other set-ups won't function properly, its just in the majority of cases the pairing above achieves the best results first time. Later on, you could go DC, lighten the flywheel to approx 2 kg and weld the centre boss to give a system that should last for miles.

we used to have a lot of problems with the rubber caps on the tiny 23cc engines I used to race, I used to jubilee clip them tight to the ceramic.

the best are the ones described above, the "plastic" burgandy NGK caps

the rubber ones in my experience seemed to walk themselves off the plugs, creating an air gap to the plug, it would still run, but with a much higher HT voltage hence killing the plug.

dont know if it was a combination of heat and cold,then vibration etc????

try a plug with a resistor like a ngk br8es