ORIGINAL: Machinegun21
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.
HUH...[X(]
Four strokes do NOT require any special fuel. Are you kidding us or what.
Any decent 10% to 15% nitro with 18% oil is fine. Cool power, byrons and a host of others all work well. Do not run the oil marked for 4-stroke engines. They actually only have 16% oil and OS and Saito will not cover a warranty repair if that oil is used. Every 4-stroke engine I have ever used/worked on wants 18% oil. It does not matter if its all synthetic or a blend of synthetic/castor
I run Saitos, OS and YS engines, all 4 strokes. The only 4 stroke engine that requires anything beyond normal is the YS. The minimum nitro/oil content is 20/20 (20% nitro/20% full synthetic oil, no castor) for YS but if you have flown one you'll understand why. These are supercharged engines and love huge amounts of nitro. Saitos will also do very well on 30% nitro but OS and Magnum will start to detonate once you get over 20% nitro and will end up blowing themselves apart and backfiring thus throwing the prop
In all of my 4-strokes for normal sport flying I use Byron 15% nitro/ 20% oil which is a castor/synthetic blend (I beleive 2% castor/18% oil) I like more only than is needed because it's just the way I am. My OS's all have well over 200 flights annd one, the OS91 which is basically the same as the magnum 91, have well over 300 flights on it.