Gentlemen, thanks for all your replies! I've been away all week on business and this is the first time since last weekend I've had to view the thread

I'm going to have a go at porting an older Leo 25 engine but I've also taken on board the other stuff about bearings, carbs, fuel and exhausts etc!

To answer a few of the posts....

Ed Cregger you mentioned that I didn't state the use for the engine - I did in post 13! They are used in r/c spad combat where the rules allow stock motors of .30 or below with NO tuned pipes because of noise. If I was a little cryptic it's because I'd like to keep it quiet that I'm going to modify my engines! This isn't because it's against the rules, it's purely because I'd like an edge in combat. I've been using an MVVS 26 with a mini pipe and it's making about 17.5 rpm on an APC 9x4, however it runs on a pipe which isn't now allowed.

Kweasel cheating is out of the question, I want to do this legitimately or not at all.

Keep the discussion coming!! I'll post back when I've done some modifications and got some results.