ORIGINAL: T28RON
I have a ST-75 and am getting 8220 RPMs with a attached to a Astro Hog Bipe. 13 X6 prop. I can barely get it up. I would think that I should be getting at least 9/10,000. I have no leaks, new fuel, and new plug. I am useing omega 15% with 16% synthetic. I was told a long time ago by a flyer that works for Hobby bench in Phx that all 15% has 16% synthetic oil. should I drop to a 12 X 8 to get more RPMs??????? Thanks.
Ron
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My ASP (first generation) .61 ABC would swing a 13x6 at a little above 10k rpm and an 11x7 at over 12.5k rpm utilizing the stock muffler. Something doesn't sound right about your ST.75. Not broken-in sufficiently? Seriously, it should do much better than that. The ST.75 is a good engine.
You might want to drop back to an 11x8 for a while. Don't want the engine overheating. Also, a bad glow plug can put the crunch on the upper numbers too. ST engines tend to run with the ignition too far advanced when running 10% or higher nitro and a warm plug in warm weather. Backing off the prop load should help considerably. The 11x8 is not too small, by the way.