I rebuilt my 48 in exactly the same manner. I used a Frank Bowman ring, new bearings and a Magnum carb. It has now been rebuilt about a year and I have about 50, ten or twelve minute flights on it now. I have always run it rich and have finally leaned it out to just below max rpm's. Wow, does this thing run good. I have it in a Kyosho spitfire and it is really moving out now. It's performance was sufficient when it was rich but now it is awesome set just at max. My suggestion is to leave it rich for a long time to really break it in right. Franks' rings are great and will give you excellent performance from your engine. The Magnum carb will let you get a really good slow idle out of it and is really necessary if you invert the engine. Even now I tried the original carb and it doesn't like to idle to well inverted.