I was given a plane that has an older ASP 1.20 2 stroke. I was test running the engine and it ran real nice and smooth however, the muffler seemed way to small for a 1.20. I checked out the muffler part number on line and discovered it's for an OS 60. So my question is how bad is it to run the engine with a muffle made for 1/2 its displacement. I was thinking of opening the muffler port to at least match the engine exhaust..

I am not even sure how well the plane will fly since it a scratch build, so I don't want to dump a lot of time into it until I can test it out in the air.

Thoughts appreciated!

Dave