having owned many brands & sizes I can say I have found no real difference in reliability between OS and TT engines. for the price TT is hard to beat.the OLD series Magnum was nothing more than a copy of the OS FSR series & ran very very well. OS priced themselves out of many peoples pockets years ago. thats not to say they are not great engines , just their ARE alternatives depending on what you want. many of these are good copies of other designs .repairs to OS will be costly for beginners & there are other motors that will serve VERY admirally for the first few planes. the old K&B FRONT ROTOR .40 was a very much used design & for sport flying served well. carburators make or break even a good design.