I have a new OS 120 III with pump mounted inverted on new GP Ryan STA. Engine cranks/runs well on ground in the air any sudden movement causing G force; snap roll, spin etc. it dies and smokes like it rich after clearing it throat back to running normal. Last Sunday it happened. Just after take off I banked and pulled a hard right turn; total shut down! Got her back to the runway at the cost of 2 smashed wheel pants and bent axle. This engine has 2 tanks break-in per instructions and about 10 flights. HELP! I hate to destroy my Ryan because of a new engine flame out. I am running Sig 10%, 20% oil, OS F type plug, Fuel filter, vented tank, 90 degree OS header, 6 inch extention with 45 degree turn down. I tuned 1/4 turn rich from max setting because of cowled engine, don't want to over heat. Any suggestions? This thing has about got my goat! How do you set this engine up?

Thanks guys,

BobHH

Is your engine quiting only at idle speed, like when you do a spin or randomly at any time on full or part throttle use?

If it's quiting at idle , try leaning out the idle mixture screw a little screw. If it's quiting at part or full throttle (and you seem to be runing at a rich setting), it might be over heating. A cause of over heating could be insifficient EXIT area in the bottom of the cowl. In order to ensure proper air flow thru the cowl, the air EXIT area has to be between 2 and 3 times the area of the openings at the front of the cowl. Open up the bottom of the cowl w/ a Dremmel sanding drum, if necessary.

One other thing, these pumped engines have to be setup differently from non-pumped fourstrokes. If you check the manual (huh, what manual you say? ), you'll see that OS recommends peaking the engine and pretty much leaving the main needle valve at that setting. The fuel pressure from the pump ensures adequate fuel flow to the engine. If you still want to be conservative, you can run it a little on the rich side of peak rpm, but IMO 1/4 turn is too much.

One final thought, you ARE leaving the tank's vent line unplugged and open to the atmosphere, right? If you aren't that would explain the engine quiting from fuel starvation.

FWIW, I have the same engine with over 100 flights in a hard flying aerobatic plane and it's never quit on me yet.

LuvBipes
Are you running your engine inverted?

Luvbipes, I am running at about 2/3 thottle. I have opened up the cowl ring with scalloping the ring and increasing the intake opening. I will try leaning it out a bit. I had leaned the low end where it knocked during transition then richen it up until it quit. Idle is good. Tank is vented. During these test I have run engine in pits with no overheating evidence. Thanks for the help.

BobHH

I dont think is overheating because just happens with , high load manouvers

Take the cowl off and try flying it to see what happens.

Does the same thing. No change in performance.

BobHH

Well at least you've outruled over-heating. Filter is clean and your clunk is not doubled back, OS "F" hmmm.....
How bout hooking up the pressure from the muffler to the tank and give it a whirl. I know it shouldn't make a difference but......

The engine is pretty new, maybe it'll work itself out after a bit.

My OS 120 III is on its second plane and I've run it both sidewise and inverted w/ equally good results.

Bob, pls reread what I wrote above, by opening the air ENTRY hole you are doing the opposite of what I'm suggesting. To improve flow thru a cowl, you can EITHER restrict the air entering OR increase the area in which the air EXITS.

For example, in my 1/4 scale Giles, I help cool the Moki 1.35 (side mounted) by completely closing off the left side air entrance into the cowl. Why? because, the air entering the cowl on the side opposite the engine, is only creating turbulence in the cowl and doing very little, if anything, to cool the engine. By only leaving the right side hole open, all the air entering the cowl is directed (in this case) directly over the cylinder's cooling fins.

Before you risk your plane again, I would suggest pulling the engine and running on a stand where you can more easily adjust it and observe its operation. If it runs well on the stand, then it's obviously something in the setup in the Ryan that's amiss. If it still acts up on the stand, then it's an engine related problem.

Just an idea, but very rarely it does occur that vibration will cause the fuel to foam in the tank and cause the engine to surge and eventually quit. Is there any way to wrap the tank in 1/4 foam rubber in that plane???

I wouldn't hook-up a muffler pressure line on this engine, by the way, because it wasn't designed to run that way, and second guessing the manufacturer is never very smart - it could very well void your warranty. I imagine your engine is less than 2 years old, so, if all else fails, why don't you pack it up and send it back to Hobby Services w/ a detailed note explaining what's going on.

Bobhh , I had a similar problem with a bipe with an OSFS120SP supercharged engine.This engine has a gear pump and a pressure regulator before the carb. It also used to either cut or sag and blow a trail of smoke then recover after violent manuevers. Tested engine on bench , and used the same tank and fuel line from the plane. No problems! I shook the tank to simulate vibration and sudden manuevers , big problem! Turns out that when i shake the tank i,m getting massive fuel foaming which the pump does not like. Engine would sag blow smoke as if it were rich which in reality is massive leanout under load causing instant vaporisation of my oil fuel mix(mix my own fuel) The fix was simple i started adding a couple of drops of Armour oil vinyl protectant to my 4 litre fuel jug on completion of fuel mixing.This stuff contains silicone which helps lower the surface tension of the fuel virtually eliminating the foaming. Guess 'cause i mix my own fuel that i'm missing some of the additives of commercially produced fuel. I also added extra vibration absorbtion mounting/padding to my fuel tank (mounted on C.G ) to dampen a bit more of the vibration from the airframe. Test flew the next weekend , result , best flight i've ever had with my CG Ultimate! The engine ran basically as it ran on the bench , awesome top end and excellent idle , not one hiccup since. Just my two cents , but id try looking for vibration isolation of the tank or an anti foaming additive to your fuel if you mix it yourself.These fuel pumps have temendous flow and pressure but have very little tolerance to aerated fuel and you can't see that happening in flight !Leon.

You guys just sparked something in my head. The fuel tank is mounted in 1/4 foam but, the outlet come out a very small hole in the firewall. It fits quit tightly around the neck of the tank. This would cancel out a majority of the isolation from the foam. I will revisit the tank issue and let you know.

Thanks,

BobHH

Change fuel from SIG ........... its bad !!
beleive me........... borrow some fuel from a freind BYRON FUEL .................that would do the trick !!

SIG's BAD

cheers