after I took the pics I put the saw back where I found it so he woudnt notice I had played with it
The bore might be 76mm as you can see a 66mm sitting in it,
It appears to be a original bottom end but can not confirm without a further tear down.
The only diff from a stock saw looks like the cylinder and piston.
as you can see in these pics there is a lot of finger porting done to this custom built cylinder.
the piston's single L ring configuration is not common in saws and could be from bike or other source.
this saw does look like it would still run but I could not locate a gas can to try it
Thank you for the info!!!
Scaling down the picture )referring to 66 mm piston) my result is about 70 mm bore.
What do you mean with "finger porting", I don't know the translation in Italian but what i know, working on motorbike 2 stroke engines is that there are porting/waste windows and channels in the cylinders.
Have you got a broken 090 cylinder (or, better, a 10 cu inches kit, but i think is rare as platinum) or how to find it? I'll try to overbore an original broken 090 and obtain a 10 cu inches one. Here in Italy 090, like contras or 070 are very rare, mines came from Germany....