I just acquired an unused 91-AC. I'm trying to determine if it is the early one with the screw-in cylinder liner or the later version, without taking it apart.
It came with a small booklet with part numbers. Can anyone tell from these which one it is?
The engine is part # YS0081.
The liner is part # YS1621.

Thanks,

Larry

The liner part number is the same as the 91FZ on Central Hobbies' site. The case on the will still be stamped AC.

aircaprc ,

Sounds like it may be the later one then. Thanks for looking up the info.

Larry