OS FS40 idle help
 

I have a used FS 40 mounted in a cub @ 90'. I have Cool Power 4 stroke fuel, new OS F plug and a MAS 11 - 5 prop. It starts great, revs great but wants to bark, spit and die at lower speeds with the glow clip removed.
What else can I try so I will be able to land this with the engine still running. Now the most reliable idle is too high for a good landing.
I forgot to mention that my engine only has the header pipe and therefore I have no muffler pressure to the tank.
Thanks,

ZB

OS FS40 idle help
 

Jimmy,

I don't have one of these, but it sounds like your mixture is too lean at idle? Doesn't it have the air bleed idle carb? Is there a way you can enrichen the mixture at idle?

Most people don't use 4 stroke fuel in a 4 stroke. They use regular Omega or Cool Power Heli types?

War Eagle, Go Tigers etc

OS FS40 idle help
 

w8ye;

I'm not saying that you are wrong, but I think the low end is too rich. :D

IMHO, spitting fuel and the tendency to quit when the glow clip is removed both indicate that the low end is too rich...?

OS FS40 idle help
 

Sandal,

You are correct. I must have had a brain fade?

Jim

OS FS40 idle help
 

Perhaps check the valve clearance. May be loosing compression?

OS FS40 idle help
 

Hello!
I run one of these OS FS. 40 20 years ago ,it was a fine performer, As a matter of fact I still have one of these new in box, never run.
At sea level were I fly I used 5% nitro and 20% castor oil (of course an OS F plug) and an 11x6 APC prop. If you fly at sea level I would think the 11x5 is way to small for this engine. I used my Os in low winged airplane designed by myself with a span of 160 cm weighting 1,8kg and I could nearly do vertical takeoffs using the above combo.

Regards!
Jan K
Sweden

os120fs
 

HELLO ZB50,IM HAVING THE SAME PROBLEM WITH A OS 120FS IF YOU FIND OUT PLEASE LET ME NO. EDDIE