Thanks for the info guys.

Does Hatori make 4-stroke "tuned mufflers" for the smaller engines I have in mind (OS 40-48 & YS 53-63's)? If so, what are the model numbers?

Kris, I've come across an older Hatori tuned pipe which is designated to go with 120 size 4-strokes. The pipe is about 8-10" long and looks just about right for a 10-12 sized 2-stroke! When I saw it I immediately thought of using it on a Webra 12 that I have but now I'm wondering what performance loss and/or noise silencing effect it would have on a 48-53 size 4-stroke. I guess I should go to my LHS and pick up that rare little pipe.

David.