Ok, I'll go with Fontyyy to a point. Avgas will go a size too lean without nipping up, whereas ULG might not, but........what is it we're trying to achieve here?

If you don't want your bike to seize then put it all back to stock, run the manufacturer's recomended settings, stick pump fuel in it and ride around all day having fun.

If you are running lean (as is), then by adding avgas you will reduce the risk of seizing mainly thanks to the avgas requiring a leaner mixture for complete burn compared to pump fuel, in effect a richer mixture. Also, the higher octane will reduce the chance of detonation.

If you're running rich now, mixing avgas will make it richer. Not a good idea.

Are you racing the bike? Do you need every last pony that can be squeezed out?

If not then pump fuel, correct carb settings and a quality 2 stroke oil will give you all the pleasure you need.

So many times engine problems can be traced back to bad carb settings.