Scooterotica

hello mick.
im not super technical with port timings in degrees although i have checked them with a degree disc in the past
i generally get the piston at btc to line up with the bottom edge of the transfer ports and the exhaust port and use packers/gaskets to achieve this...then worry about getting the squish correct by either the head gasket thickness or in my latest engine i had to alter a head to sit into the barrel
its a bit basic this way and the techno guys will no doubt have an input
but it should be a good starting point for you....
just wouldnt like to to start welding ports if you didnt need too

Sorry should have been clearer.

Is your crank a 60mm with a 110mm rod?

That might explain a 2mm overlap. The piston will be 1mm lower at BDC compared to a 107 rod in the same barrel.

I think the standard barrel is 101.5mm between the gasket faces, but remember that some casings can vary in the face height which can cause problems in trying to get the timings right. Ideally assemble with no gaskets then work out what packers and gaskets you need to get the desired timings and squish.