Hi Eugene:

Thanks for the conversion numbers on the wallbros´ carbs. On the muffler... I bought the US41 at Tower Hobbies when they still sold it, and it came with a different muffler than advertised. They call it the Alluminum muffler, which is round and has the two pipes. Looks better than the can one, it is lighter and is louder too. So I am not sure if this works already for increasing final rpms.
Thanks again, I am starting to like this engine every time more, so many possibilities!!!!
Great Flying
Cris