What's your opinion when upgrading a 50cc 2t minarelli to 70cc - leave the autolube system as is or completely avoid and premix the fuel with 2stoke oil?
Personally I'd leave the autolube system as it is. Premixing is more haphazard as it depends on the quantity of fuel you have in the tank at any given time.
Go pre-mix.. Have a pre-measure for every full tank,better safe than sorry. Had a lot of 2t singles when younger,alot had a upend the cap measure,simple full tank & single measure.
I will have the engine fully rebuilt including new oilpump and oil pump gear, crank etc.. I will do my first tank with premix until I'm sure the pump is well primed as I'm really not sure how to prime it properly
From a pro. Do as you said, first tank gets extra oil, after run it with the oil pump, I've not seen a Yamaha oil pump fail in my years working at a dealership. You can run the first 2 tanks with extra oil if you want. And use good synth oil, not cheap mineral shit.