I am going to be buying a YS 91 here in the next month or so for a Great Planes Giles 202 45-60 size. I am wondering what would be the best fuel to use in a YS that size? I use Byron YS fuel for my YS 63 and it runs like a charm. Stick with the Fuel??? Got any suggestions??

Jake

From memory (don't have the manual handy), I think the recommended fuel is between 10 and 30% nitro, 20% oil.....don't quote me on the oil content though. I mix my own fuel and run 20% Klotz (totally synthetic), 20% nitro and remainder methanol. The engine sings on it......no need for higher nitro at all. I'm getting ~9000rpm on the ground with an APC 15x8 prop. Heaps of grunt for the 120 sized Ultimate Bipe it's attached to.

Run powermaster YS 20/20 or Wildcat YS fuel. They both have 20% notro and 20% synthetic oil. Castor will run but clogs things in the regulator up.

Scott

YS engines love high oil, namely 20%. They also like higher nitro amounts than most other 4-strokes. I like 20% to 25% nitro in YS 4-strokes.
Don't be afraid to run a fuel with just a touch of castor in it. Through hundreds of gallons of running YS 4-stroke test engines, I found that 18% synthetic and 2% castor will not gum anything up in the regulator or coke up the valves. Any more than 2% castor over an extended period of time, the valves will start building up deposits and the regulator gets gummy if they sit for long periods.
All synthetic is fine too as long as you run it at 20% by volume.

In addition to the Wildcat and Powermaster, Cooper's and S&W fuels are also compliant with YS warranty requirements.


Fuelman

YS recommends 15 to 20% nitro. They run great on 20%. Too little nitro and your throttle response is poor and the power is way down.

I run Powermaster 20/20 in mine. 20%oil 20%nitro. The oil residue out the exhaust is clear and clean. They must use some high quality oil! By the way it is all synthetic. A pattern flier told me to stay away from castor. I do believe that 2% will not hurt anything though.

That YS will REALLY love 30% heli fuel . It is high oil content and high nitro. The engine starts better, ldles longer transitions flawlessly and puts out great power. The fuel literally RUNS through he engine, keeping everything cool. You'll burn a tank faster - watch your time - but your engine will LOVE it.

-Cheech