jdavies300s

ok, i just got an o.s. .61 fx, i need to tune the engine, but i can't seem to do it by sound. i have a tach, and am curiouse as to what the perfect, or ideal rpm should be at idle. at all settings the plane will go through the rpm range cleanly with a good transition, so it is hard to tell if it is lean or rich. please help!!!!

thank you in advance.

-james

<~~in the plane you see there, hopefully plenty of power

FHHuber

Which prop is on it? The longer (and heavier) the prop, the lower the idle can get.

The better the engine is broken in the lower the speed it will idle (until the thing starts to wear out...)

I've gotten a O.S. .61 SF to idle as low as 1400 rpm and be stable, without glow hooked up. With glow I've gotten one down to 900.

Generally... 2200 is considered doing good with a relatively new engine.

If the engine is idling smoothly... and not pulling the plane along at 20 mph... its probably OK, based on what you have said.

jdavies300s

it's got a 12x7 prop on it right now. it's not a new engine. i didin't do the break in either. last time it ran hot regardless of setting, but then again we hada 4 stroke plug in it. i'm just trying to find a good rpm for it. 2200 sounds about right tho. thanks.

jaka

Hi!
12x7 is a bit large.... try a 12x6 APC for general sportflying or a 13x4-5 for a scale warbird or a or a 14x4 for a slowflying bipe or highwinged airplane or a 11x71/2 - 11x8 for a old style pattern bird.
This is for sea-level conditions.
Regards!
Jan K
Sweden

jdavies300s

i am basically at sea level right now. i don't think you get much closer than what i am at. i am flying full aerobatics. the engine is in a segull models 300s. that was the recommended prop for the plane/engine combo. i will need the extra thrust for the aerobatics n e way.i found out the high rpm on it. or at least what some guys said it would turn w/this prop. he said it'll turn up to 12,500rpm with a 12x7. he didn't know the low though. i want to make sure it is set right so that i don't burn the engine up in the first month which i have seen done before. i might switch down to a 12x6 just to try it out. but i want to fly it with the 12x7 a few times first to get used to it, and then i will have something to compare the flight characteristics to.
thanks for the advice.

daven

My Feedback: (1)

I have an O.S. .61 FX that runs absolutely perfect. Probably one of the best running engines that I own. I also like the APC 12x6 prop for it.