what type of fuel is everyone running in this engine? I have a 46 fx that dosnt like the castor oil from what I see. I didnt know if this was true with os or if its just me. I have some 30% nitro would that be to much?

For the O.S. Max 1.20 AX engine, you'd normally use a fuel with 5%-10% nitro and at least 18% oil content.

For the non-ringed engines, such as the .46 FX or AX engines, you'd use a fuel with 5%-15% nitro content and 18% oil content. In these engines, though, you'd want the oil mixture to contain castor oil. Non-ringed engines do best when the oil content contains a goodly portion of castor oil.

With nitro content above 20%, you may need to adjust the compression ratio of the engine by adding additional cylinder head gaskets to eliminate detonation. That's common with high-nitro fuels, and may be why your engine "doesn't like" the castor oil...the high-nitro fuel's the problem, not the castor oil.

my 46 fx likes the 30 % nitro but wont run good with the 15% nitro and caster mix?

Non-ringed engines will take a "set", depending upon the fuel used. If you go from a high-nitro fuel, like your 30%, and then go to a low-nitro fuel, like 10% or 15%, then the engine may not respond well. Some will take some running time, others won't "come in" at all on the lower fuel. Usually, with non-ringed engines, you can go up in nitro, but not down. That's for large changes in percentage, and for percentages over 15%-20%. You can usually go back and forth between 5%-15% nitro fuels with no problems. It's not the oil, but the nitro content that's causing your engine's difficulties.

Ringed engines can usually take wider changes in nitro content, but you'll have to account for the need to change the compression ratio to suit the fuel.

I Have 2 OS 46 FX's, 3 OS 50 SX's, 2 OS 55 AX's, OS 61 FX, OS 91 FX, and 3 OS 120 AX's. I run all My Engines on Morgans COOL POWER "Green Colored" 15% Nitro Fuel ONLY. NEVER use Other Fuels or Higher Nitro Content. I only occassional put some After Run Oil in them if I'm not going to run them for long while. I break all My Motors in the Way OS Engine Manual says and they All Run Super. Propping and running Slightly Rich like manuals recommends seems keep them performing better than other 2 Stroke Glow Engines. I Have allot Props in all different Sizes and Pitches. Propping How I get Better Performance out of My Engines. Experment abite and You'll be Happily Surprised. Also Your Engines will Run and last longer. The 120 AX with APC 16 X 4 Wide Prop works great on My 3D Airplanes. Use Tach see which slghtly rich gives close 10,000 RPM recommended RPM for that engine. They Lean some in Air And Turn More RPM. I think can Gain close 800 RPM More in Air with many Props. So I like set My 120 AX at about 9000 to 9500 RPM on Ground and in Air They Fly Supper with those APC WIDE BLADE 3D Props. Happy Flying. richgrow