Gerry

The Sach's as you mention is most likely a Sachs cylinder/piston assembly built into an aero engine and or a Chainsaw engine converted to aero use. Do you know the manufacturer? Sachs/Mahle/Makita/Dahlmer and others are all of the same cylinder assembly manufacturer.

I would suggest a Menz S. There are many manufacturer's out there, many are built and offered for a variety of different applications.

Look for a maximum around 6500rpm. Anywhere between 5500-6500 should work fine without causing problems.