OS 120fs Pumped
 

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

RE: OS 120fs Pumped
 

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.

RE: OS 120fs Pumped
 

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.

RE: OS 120fs Pumped
 

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

RE: OS 120fs Pumped
 

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?

RE: OS 120fs Pumped
 

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.

RE: OS 120fs Pumped
 

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;)

RE: OS 120fs Pumped
 

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]

RE: OS 120fs Pumped
 

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

RE: OS 120fs Pumped
 

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]

RE: OS 120fs Pumped
 

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