You get what you pay for!
Yes, Quality is directly propotional to cost in this case. See my post on pg 2 now under Magnum 91 tuning. The Magnum 4 strokes run ok. If you're a sport flyer Not trying to get that last rpm out of the engine, you might be happy with Magnums. Carefull though, I'd hand pick one from your local hobby shop and hope they have several to choose from. I went through a half dozen before I found one without any visible flaws, ranging from forging laps to broken valve covers. The lowest grade bearings are used and if you forget to put afterrun oil in it they'll be rusted in a day. Its hit or miss to get a good one. The money saved is in the production and the workmanship is poor. For what its worth, the magnum 91 I have runs well, I think I got lucky. Bought because it was $150 on sale and went on a 60 trainer.