G'day

I am confused. There appears to be a four stroke exhaust in your photos? Third photo across.

That four stroke muffler is NOT for your engine. After all, there is nowhere it would fit. I think you have gotten a little accidental present which fell into the wrong box.

Or, do you also have a Magnum/ASP 52 or 61 four stroke?

I would use an 11 x 6 for running in and for initial flying. Lower load on the engine. I would also use a fuel that has some castor oil in the mix. I have had several Magnum/ASP engines and they all were easier to run initially with some castor. I use 10% nitro, 5% castor, 15% Klotz 200 and 70% methanol as my standard fuel for two and four stroke engines. With 10% nitro, I would use either an Enya #3 plug or one of the Hot Merlin plugs. My new Jett 46 came with a Merlin 2003HD which is the heavy duty version of the 2003 Hot plug. I have ordered some from Merlin's web site and am waiting for them. Very easy to do and the price is excellent.

Cheers

Mike in Oz