Originally posted by TRAJ
If it is a "small block" meaning the crankcase is the same size as a .12 crankcase then you can fit the NS12 3/5port internals.
TRAJ, I think that is incorrect. Looking at the Novarossi site, the only thing that the NS15 engine has in common with the NSR12 is the following;
Conrod
Main Bearing
Front Bearing
Back Plate
Carb Locking Pin
The piston sleeve and the crankshaft is definitely not the same...