The 4-cycle engines create more torque and take a more speacle kind of fuel. the kickbacks are caused becaused it is such a large cylinder and since it has to compress alot more air it can kickback and actully run backwards but if you start it right (witch is not hard to do) you should not have to worry about it. plus the Magnum 91 is a great 4 cycle engine, i got mine (also my 1st 4 cycle) about 10 months ago and it has been a great little engine.