I have a Fantic 240 & a 301 both of which are recomended to run on 2% premix ratio, but this ratio is based on the 2 stroke oils available 20 years ago when the bikes were new. How lean can I go with the amount of modern fully synthetic oil without causing any damage?

Fuel choice locally is Premium unleaded or Super unleaded, I always use Super, the 301 still pinks occasionally on a long climb on a hot day though.

If the machine surfaces are in good shape, you can try removing the head gasket to tighten up the squish clearance.

The old school method is to use metallized spraypaint to coat both surfaces and assemble while still slightly tacky.

Sometimes it says on the label if there's metal in the paint. All paint that said it gave an 'aluminum' look used to have it, and I think all of the 'chrome-in-a-can' paints have it.

I've run bikes like this for years, but if it makes you nervous as a long-term solution, it's a good test to see if it helps your problem before you start removing metal.

You should also check piston-to-head clearance to make sure nothing is going to hit.

I put 'silly putty' on top of the piston and crank the motor.