GoBucks

I have an OS .55ax that has dead sticked the last 4 flights. It's in an Aeroworks profile and I'm running Magnum DS30 heli fuel. I noticed air bubbles in the fuel line so I replaced all the fuel lines and installed a Dubro bubble less clunk but still get some air in the fuel line. Yesterday when playing with the high needle I couldn't get it to run "too rich". We had the high at least 4 turns out and it never sputtered or acted rich. This tells me it's sucking air from somewhere. It's less than a year old and has less than 1 gallon through it. Should I just send it back to OS?

1QwkSport2.5r

Richening the needle way out and not getting the engine to run any richer tells me there's a fuel restriction or there's a lot of air bubbles getting through to the engine. I would be ensuring the carburetor is clean - namely the needle valve holder. I'd also make sure the tank is padded well. A tank that isn't isolated well will allow the fuel to foam up and the engine to pull those air bubbles in. Any air in the fuel line will lean the fuel mixture - in some cases considerably.

TFF

Is the prop in balance?

jeffie8696

Yea, what they said

LSP972

My Feedback: (13)

I've had the same problem. I broke it in on the stand, as they described, two 10 ounces of 15% Cool Power, ran fine. I installed it on a Sig SE, good tank, good lines, everything looked good... and the engine quits suddenly, for no apparent reason. Doesn't matter whether the mixture is rich, lean, or right; it just quits. Sometime in a couple of minutes, sometimes in half a tank (10 ounce in the model).

A fellow flier has the exact same issues with a .65AX; and we checked everything out in detail. Nothing seems to be wrong; but it quits too for no apparent reason.

So much for el cheapo Chinese OS engines. Well, the PRICE isn't cheap, but I also have a couple of 25 year old .46 SF and one .40SF on some old kits I built back in the day... and they still run quite fine. I'll never buy a new OS engine again, thats for sure.

I'm looking now for an OS .61SF I'd like to find new or near-new... lots of luck there, nobody with any sense who has one is letting go of it.

.

aspeed

I don't think it makes any difference what country it comes from. The machines that make them are the same. It is likely something simple like a hole in the pickup line inside the tank, or a leaky O ring on the needle, carb hold down or some other similar air leak

jeffie8696

Did you replace the engine on the plane and the problem went away?

LSP972

My Feedback: (13)

I do. And for what it's worth, both of the engines I was talking about in my post here had EVERYTHING checked, on the engines and the airplanes, by two people. Both of us have been in this hobby for over 30 years each... So we've had a bit of experience with these simple glow engines.

The guy who started this thread is not the only person I've heard who has had trouble with these particular engines- not counting the two I've seen personally.

Apparently, some folks have good luck with these; and some folks don't (through no fault of their own). I won't try any of them again, that's for darn sure.

.

Mr Cox

To me this sounds like the low-end needle is too far in, it will then restrict the fuel flow even at full throttle and the main-needle cannot correct for that, no matter how far out you put it.

So back to square one, set the low-end needle well rich, then tune the high-end needle at full throttle (it should now give the appropriate respons). Then go back to the low-end and lean it just enough so that you have a good throttle response from a high idle (about 1/4 throttle) and up to full throttle. The idle it-self will then depend or how well they made the carb, just live with what you get there, you cannot tune the low-end needle for a super clean running at a low idle.

Ideally one should have three adjustments, low-end, mid-range and high end. But most engine manufactures have settle for just two, the "low-end" one covering the mid-range (potentially affecting even the full throttle needle setting) and a main needle setting. The only way to tune the low and midranges independently on these carbs is through the taper of the needle. So in principle they should provide a few different needles with the engine...

Keep in mind that the settings are affected by the fuel and propeller choice too, so a Helicopter fuel might not be the best choice for the engine.

jaka

Hi!
30% nitro?
Try 5-10% instead.
Too much nitro gives the sympthoms you describe where an engine suddenly stops when the glowignitor is removed. Engine runs and throttles perfect but. stops at low rpm or at idle.

As for the bubbles in the tank, is is most due to a tank leak.This is my experience from flying pylonracing
for nearly 40 years.

spaceworm

IMHO, bubbles in the fuel line cannot be OS's problem, it is yours. There must be a hole or crack in the fuel line(s) from the tank to the engine for this to happen, or not enough vibration isolation for the tank so that it foams up. Is the prop well balanced? You say you replaced everything, but apparently you missed something. I suggest you recheck everything, and also do what others have suggested re. the needle settings and percent nitro. Good luck. Please report back after you find the problem, even if it is something you missed. It happens to all of us. I have probably a dozen OS engines from CL era to recent production, and although my preference is Saito 4S, the OS have never given me problems. I have been flying and running engines since 1953. Good luck.

jaka

Hi!
As I said earlier! The symptoms you describe is due to too much nitro!
Why use 15% nitro when all glow engines run as good on 10%...or 5%.
As I have some decades experience of running MVVS glow engines I can say that some of them cannot even be run on 10% nitro. And some 10-15cc (older ones) cannot even tolerate 5% nitro.

blw

My Feedback: (3)

Make a shim and your 15% nitro problems will vanish, Jaka. You already know this.

Bax

My Feedback: (11)

If the engine is trending lean and you can open the high-speed needle a lot and it still is running too lean until it suddenly drops into a very rich setting, you have vibration-induced fuel foaming. That means that the engine's vibrations are agitating the fuel enough so that air gets into it. This essentially leans the mixture. The engine won't richen until you have it so rich that the amount of fuel entering the engine makes it drop down the the lower RPM and then the vibrations are enough less that the air comes out of the fuel. As you re-lean the engine it will lean gradually until it will suddenly become lean and jump to a high RPM.

This problem is especially noticeable on profile-type models, where the fuel tank is hard-mounted to the side of the plank-type fuselage. You have to use some kind of vibration isolation to get the fuel tank away from the vibrating wood. A good layer of foam rubber can do this.

1QwkSport2.5r

A Tettra or BubbleJett fuel tank may be worth a try if fuel foaming is indeed the problem. Running the engine on the test stand with a known good fuel system (padded tank and rigid mounting of engine) should be in order to isolate where exactly the problem lies.

jaka

Hi!
Agree BLW, Putting in a 0,1mm head shim can fix it.
Yes! A Tettra "Bubbleless" tank is the best fuel tank there is.

Bax you are correct, it could be due to vibration or...a hole in the fuel tubing or tank, but my recommendation is worth trying. I know that all OS engine could be run on anything from 0% to 15% (or more nitro) without problems but why use 15% nitro when all engines run as good on just 10% nitro...or 5% as I use.

Bax

My Feedback: (11)

Jan,

I agree.

For the most part, unless the utmost in performance is wanted, lower nitro is better. The engine usually handles better, and the fuel has lower cost. 5%-10% for almost all users is the most needed.

jeffie8696

You cant even sell 5% to my club members, except me and my buddy Jeurg. Everyone at my club uses 15% as a minimum. Just the other day I ran my rebuilt OS46FX and tried some 5% and it ran just great. The better quality engines will tolerate low nitro while poor quality engines like higher nitro , also poor tuning gets covered up by lots of nitro.

1QwkSport2.5r

On the bold - I agree. That's probably why everyone uses it. The tuning window is a mile wide - you may have half turn from rich to lean.... Of course then the operator/pilot wonders why his plane always deadsticks.

jeffie8696

Seems most flyers want to "tune it and forget it" not understanding that the engine changes during breakin and the tuning changes with atmospheric changes . I give mine a tweak every flying session , it takes a few seconds.

1QwkSport2.5r

I do the same. Oftentimes both needles need a tweak. I always Richen the main needle 1/4 turn before firing the engine up and readjust after getting warmed up. That's another issue - setting the needle before the engine is fully warmed up. These engines lean out as they heat up, so if you set the needle too lean before its fully warmed up, it'll be too lean when it is warmed up.

aspeed

It is over a month now, have you got it going yet? Maybe a cheek cowl for strengthening is in the works. I have a flimsy motor mount on a plane that shakes and makes the tank foam up like crazy. It does not seem like it shakes that much but that is the problem. It clears up in the air because of the centrifugal force as it is control line, but an RC would get no better in the air.

jeffie8696

My Nexstar had issues with fuel foaming, I replaced the tank and isolated it with foam and changed the metal mount to a nylon, problem solved

J330

My Feedback: (3)

Funny posts. I remember reading people complain about Fox, Perry carb equipped K&B engines, Webra Dynamix carbs, and Super Tigre.

They're all gone, and what company survived?

O.S.
I have seasons of AX 55 and AX 65 flight time,
never a problem. I use 10% fuel, and a hot plug, McCoy 59.

Plenty of 61SF engines around, keep looking, but what would you do if the SF gave you the same symptoms?
It's not the engine.
It's only got a crank, rod, and piston,
and the best carbs in the world, their claim to fame, and for it's user friendly nature, outlasted the rest. Certainly not as fast as a YS, or a Rossi, but clearly far more mainstream with sport pilots.

Did you replace the glow plug?
Where do you suppose air is leaking, and did you seal it?
Carb hold down screws, o ring to the needle, o ring at the base, or even the backplate can't give you an air leak.
Did you remove the needles and flush fuel through the carb?

ASP/Magnum, MDS, and a Mecoa engine are the only junk engines, that gave me deadsticks, and I sold them all and never went back. But Saito, OS, HP, Rossi, and Irvine are all I choose to buy, and always second hand.

Declare your issue in your ad, sell that OS,
and this one looks healthy enough.
Good luck tuning this carb, looks like a 7M with mid range adjustment. http://www.ebay.com/itm/201645695100...MakeTrack=true

http://manuals.hobbico.com/osm/27481000-manual.pdf

Don't blame an OS, blame the lack of troubleshooting the basics.

SF for sale might be a ringed engine, hopefully. SF nickel isn't that durable. As soon as it comes in, pull the head, pull the sleeve and check for a peeling nickel liner.

I can't count the engines I've had to put a piece of fuel line over the needle to seal an air leak as the o ring didn't do the job well.
Check the pressure line to the tank too.
Put the SF on and try things in flight before you sell the .55.