Bill: I purchased an older engine from a club memeber, in a box that is labeled OS FS-91* Surpass 14.96c.c. . After getting it back from Hobby Services for their review (Parts too old ,go to any on-line service guy for parts) I decided to tear it apart myself and notice the exploded view of the engine is NOT what I have! The back plate says" O.S. FS-90 model 1901. So I need to know, how old is this model and if I can get a diagram showing me the parts. ps. I also bought a guide from the RCM library for "OS model 4/strokes for engines pre 1991. NO help. My engine has the glow plug up-front near the prop! Thanks for any assistance. Mikel-T.