Hey Guys,

Just looking for some advice. Fuel and Props for my OS 120FS. For some good 3D, what would you suggest for a prop size for this bird? And what % of fuel would you recomend? I'll be using morgan fuel. I'm pretty new to 4strokes, so bear with me.

Thanks for the help
Greg

APC 16x4W or regular APC 16x6,maybe 17x5 or 17x6 if available.I use a wooden JFX 16x6 on my non pupmped 120 and it does best with it.

I have been using 30% heli on mine,many said i was wasting my time,but I had some improvement as i was borderline on power with Funtana X100.
Try some 15 -20% that should work for you.if the motor is new,avoid prolonged lean runs and use fuel with good oil content.

Somebody told me he went through too many glow plugs on 30%, have you had any issues with that?

I've read other opinions that "the OS 120 4 stroke doesn't gain from anything over 20% nitro content"

Your 120 sounds good, I may try the 30% too

What fuel do you use?

I did buy a gallon of "Cool Power High Performance Heli 30%" but don't care to replace the glow plug excessively

Thanks for the input. I was thinking somewhere along the lines of cool power pro pattern 20%. I think I have a gallon too, so bonus. I'll try the 16x6 and 16x4w too. Whats a reasonable RPM to shoot for?

I think its coolpower,never replaced the glowplug,but in my flying style,i dont ask too much from the engine,like hard lean runs.
Any full power runs are short lived during my 3 D flying.
Also I only use 1/2 tank of fuel in 10 minutes,because most stuff is done at 1/2 power.
I am at sea level.

I hear you about "short lived" on the "full power runs"

I have a goldberg ultimate with the same motor and throttle management makes that plane fly so sweet

It actually took some practice

I have a 15/8 graupner on the ultimate and back when I was flying that (on 10% coolpower) I didn't practice alot of hovering but flat spins, especially upright, were as good as it gets

I managed 2 elevator servos mounted under the stab[8D]

I forgot about the Graupner 15X8 .Its a nice prop and sounds real cool too ,when you wind it up.I strictly used that prop when I flew sport aerobatic and used the 14x7 on my OS 91FS

Ya'll aren't gonna believe this

I just brought down my ultimate with a os 120 mark III and after 6 years of sitting and with no after run oil I took out the plug and valve cover and sprayed wd-40 in cylinder and down valve push-rod guides and fueled it up turned it over for 30 seconds,,, put plug back in and it started on the first compression[X(]

I opened both needles 1/4 turn and then just tweeked them a bit and the motor runs PURRRFECT

I have a 3 position idle switch and the highspeed idle sounds good as well as the landing idle and the kill position still works[X(]

I'll say this much

The OS 120's sure seem reliable[8D]

yes,they may not be the most powerful kid on the block,but they are always reliable and put out when asked to.