cozment

My Feedback: (1)

I've got an OS .91FX 2 stroke on an .60 size extra 300 plane. This is the biggest 2 stroke (and first ringed engine) I've ever dealt with. I'm turning a 14X6 prop and running 15% cool power fuel. If I adjust the high end needle valve just right on the plane while it's on the ground like all other 2 strokes, it acts as if i'm running it extremely lean by the time I'm in the air. I'll give it full throttle but it will only run at 1/2 power. I have to land my plane and turn the needle value almost a full turn richer to make it perform full throttle. When I give the plane full throttle in the air or on the ground at this setting, it sputters and eventually catches up. I like to have a good throttle response and good performance in the air but I can't seem to find the right combination with this plane. Has someone else had these same problems and if so, offer any suggestions?

FHHuber

Sounds like the ring hasn't seated yet. Only a couple tanks through it?

Forget setting the idle... it won't set correctly if the ring's not seated.

Do a bench run with a 13X8 MA black nylon prop. Run at the edge of too rich. It needs to get too warm to be comfortable to touch, about 1/4 to 1/2 turn open from peak rpm. Be prepared to run a FULL 12 oz tank at constant full throttle. (maybe 2 tanks...) When the ring seats, the rpm and tone of the engine will change suddenly. IMMEDIATELY retune the way you'd normally adjust the ABC, non-ringed engine's you are used to., and run at appx 75% throttle (varying from 50% to full is OK)

The main needle setting can change by over 1 turn when the ring seats. sometimes... it takes several tanks of fuel to seat the ring.

That should cure it.

If you store the engine... make certain you clean it of all fuel residue by removing the glow plug and use a starter to turn it over, drawing from a small fuel tank with 1/2 oz of after run oil in it. Draw ALL the oil through the engine that way, and there should be no problem with the ring sticking (which can make it nearly impossible to start the engine after its been stored 3 months or more)

twostroker

My Feedback: (37)

Sounds to me like the low end needle is not adjusted properly. Since you are flying it already it's probably broke-in, maybe not all the way but close.
The low end needle is a mystery for many modelers, it shouldn't be. The next time you go to the field, tune that low end needle, here's how.
Start the engine as you always do, let it warm up, remove glow heater before tuning high end needle(always), tune the high end needle as you would anything else. Next your going to let engine idle as low as you can without stalling and pinch the fuel line off as close to the carb as you can. LISTEN..... Did it rev up before it stalled( I bet it did). That means the low end needle is to rich and throttle responce will be very poor. Lean the low end needle 1/4 turn. Restart, and tune high end needle again. Now repeat the fuel line pinch again, listen. If the engine idles with no change and quits abruptly, it's perfect. If the engine slows down and then dies you leaned the low end needle to much, richen it back up.
My guess is you will have to turn the low end needle more than 1/4 turn either way to tune it properly, just remember to retune high end needle after every adjustment. This will ensure the proper amount of fuel is being delivered to the carb in the first place, therfore giving you true readings.
Re-cap; Pinch fuel line off at idle, engine revs before stalling, low end needle is to rich.
Pinch fuel line off at idle, engine slows to a stop, low end needle is to lean.
Pinch fuel line off at idle, engine idles fine then stalls abruptly, low end needle is perfect ( haven't had one do this yet, it's hard to get one perfect).
This will improve your throttle responce to instant. And flame outs will be something of the past, it's like a whole different engine .

cozment

My Feedback: (1)

I've ran about 10 tanks of glow fuel on this engine. Would the rings still not be sealed even with that many flights on the engine?

twostroker

My Feedback: (37)

It definetly has enough fuel thru it to tune it properly. OS is one of the easiest/best engines to break-in, but is it broke-in all the way, probably not. That ring is hard, and so is the cylinder, it may take some time to be perfect. Even if you run it a bit rich after you tune the low end needle, you'll still have good throttle responce. Once you are sure it is broke-in "let it scream".

cozment

My Feedback: (1)

Thanks for the help. I'll try the low needle value setting this weekend. You're right about the breaking in part. I know this engine is no where near being broken in. I've just never seen an engine that was so hard to adjust even if it hasn't been broken in. Since this is my first ringed engine, I guess they behave different than the common ABC style engine.

bignasdy

I tell ya, its the same old thing around here. Ditch the cool power. I've been in this sport since 1970 and I have never seen a motor with cool power fuel run right. Thats just my experience. Get the castor dude! Just like the guys that burn up engines at the feild every weekend but refuse to listen to experience, "You gotta be smarter than the equiptment". I also bought an MDS .78 recently just to prove the "pencil sharpeners" at our feild wrong as usual. It runs great, broke in perfectly, and is very reliable. Never a flame out. When all my o.s.'s are finally fried, I'll be replacing them with the russian engines. I have tons of old o.s.'s that I either cant get parts for, or it cost more than a new engine to repair. Even my k and b's run great. what a joke, but true. yes, I am a rambler, but I wouldnt steer ya wrong. Try the Omega since you like morgan fuels, and you will see that your new os will run perfect, if its close to proper adustment.
david
p.s. dont flame me guys, til ya prove me wrong!