4 stroke Magnum engines
I have 2 magnum 91 4 stroke engines and a few of the pilots that fly with us have 91 fs and I have seen a few of mag 52 fs . They seem to do just fine . They take a little bit to break in , but if you run them rich you can fly them while you breakem in..So far mine are 2 years old and several gallons through them . Stll good comp. good rpm and sound like a honda 90 . I have a new bi-plane thats going to have the 120 fs onit .so to each his own.....