Hmm, re-reading my post, I might have given the impression that I think stock Irvine engines don't produce power out of the box. Actually, the ones I've seen have all produced solid power. I do think their carb has some issues, and the prices I've seen for them make them close to, or more expensive than an OS, so between an Irvine and an OS, I'd personally go OS for the same price.

The Magnum, however, is enough cheaper to make it worthwhile for me to run them. They do shed carb parts, so you have to work on the carb before running to fix it up, not at all unlike what AJ was describing for the the Irvine. First step is to remove the throttle stop and barrel retaining screws and put them back in with a generious amount of locktite. When you mount the carb to the engine, again don't skimp on the locktite. I've also been replacing those screws with slightly longer ones from the local Ace hardware. The replacements also seem to take a screwdriver better. But the key with the Magnums is putting fuel tubing over the high speed and low speed needle valves. A bit of large diameter tubing over the low speed screw will actually touch the screw where it sticks out of the black houseing a little, and prevents it from turning and stops air leaks all at once. A bit of normal fuel tubing on the high speed needle stops the air leak, and really makes the needle a lot easier to set right. With out those fixes, the Mag carb will self-destruct.

Btw, one of the really REALLY cool things about combat is that engine power is not super-critical. You can win with a little less speed and power. I've been using stock Mag .15s in A class against guys with more powerful OS CV-As, Norvels and other engines, and I do pretty well with them. It's much more important to know your engine and be sure you can start it on time, every time, and keep it running though the heat. I'd trade 1500rpm for 100% reliability any day. If I ever get my airframe problems sorted out in B class, I might actually be dangerous there too.