RE: Hanno MKI and MKII
Gene,
It might be faster to post the diagrams here. As for the crankcase differences - they are dimensionally the same. The exhaust port is relieved for the hanno. The early RFs had a smaller rear bearing, but that is only apparent if you take the engine apart.
I have run lots of different combinations of OS parts (as well Shadel parts). It is pretty easy to relieve the exhaust port on the stock case with a dremel tool.
Can you post some photos of the exhaust porting in your engine?
My first YS AR only lasted 55 flights before a catastrophic crash. Bent the crank and deformed the case. I sent the engine in for repair; it was returned with a short note: cheaper to buy a new one. I found one well used for $100. Rebuilt it with all the good parts from my crashed engine (piston and liner were still virtually perfect) and ran it for a long time without a hiccup - still have it!
Will Bartlett