I am looking to buy a used YS engine in the 110 to 140 size.There seem to be a lot of suffixes such as AC,SC,L,Z,etc. Can anyone explain to me what they mean? Thanks!
Rusty

AC originally meant, Air Chamber. SC was known by some a Super Charged. This is somewhat incorrect though as all YS 4-strokes are super charged. The rest of the letters mean nothing just as the current OS 2-stroke engine designations don't mean anything. FX, VX, SF, S.

John

Thanks John. What does "air chamber" mean? What is the purpose of it?
Rusty

The air chamber us a box between the carb and head. It is used as a plenum to increase intake volume. If the engine is designed for it, it will result in more power. See the diagram of the YS .91 at http://www.ysperformance.com/prod91.htm and you will note the square box on the back of the engine. I'm not familiar with all of the engineering behind the AC, but the .91 is the only engine which currently has one. There was a 1.20AC model in the past, but the chamber was removed on later models.

John

Thanks John.