RCU Forums - Roto Motor

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Building a Bruce Tharpe "Flyin' King". WS 80.5.... WT 9.5-10 lbs. Thinking of putting this Gas Roto Motor 25cc in her. This would be my first gaser. Anybody have thoughts good or bad about this motor. Thanks

I bought the 50V2 also and I think it's a good engine for that plane. Shosho was probably going gentle on you. Not forcing you to go too big since you're new on the gas engines.
I think you'd be happy with either one.
It is only your choice how much power you want and how comfortable you feel with all the power.
He's good with guaranteed statisfaction.</p>

Good luck with your flying!
Jack</p>

I had a Roto 35, it was reliable and quieter than most of the glow planes at the field. I measured the db's and it was 92db at 9 ft with the stock muffler.

Feb 19 2013

I have a brand new Roto motor 25cc I can't tune the motor to run as expected.
Facts:
Non-othanol 90 0ctane with a 50:1 oil mix.
Have run both 17x10 two blade prop, and 16x10 three blades.
Ignition battery is a 4.8 Volt with the heavier duty servo wire. Reasonable wire run no extra extentions.
Motor will not turn over 7000/7200 rpm. Mfg'r says should be 9000!
Motor starts fine, but when given the full throttle (even after warm-up) the motor dies.
Carb has been set from factory specs to really rich on the low end, with still the same result, and I have tuned the high-end from factory specs to really rich to barely lean and the motor runs the same. NOW there is some differences with tuning this much like sputters, stalls , and such. But it doesn't improve to run as expected.

My thoughts are that the gas being 90 octane non-ethanol may be not high enough?
Or! that the carb needs some special setting beyond the mfgr's settings.

OR ??? Someone out here will be able to help me.

Steve

Steve, those props seem really large for a 25cc. A G-62 runs a 22X10 and you are running a 17X10 on less then half that displacement.

Steve yes indeed I really agree with SRT and those props seam way too course for that 25cc, diameter perhaps but pitch no thats pretty darn course. I definately would avoid the three blade prop as well.

John