Wingspam

I have been using Os motors for around 5 years now, and have Never had any problems until now...

THis is my 5th Os 55 Ax, this motor now has 2 gallons of fuel ran thru it, I am having a problem with it quitting on me. I put this motor brand new motor on my new Seagull edge 540, the 40 size plane. I now have had 6 dead sticks on this plane the last one was this past Saturday.
I had about 4 flights on the plane that day, in a rotation of 3 planes. All the prior flights had been fine, the last flight the motor died about 20 feet off the ground and resulted in a hard landing. The canopy ejected (breaking the mounting tabs) and the gear ripped of the plane. Checked the fuel level it was about half full.

Everything for this motor was new, tank, tubing and of course the glow plug.

The first couple of dead stick's was because the motor didn't have enough cooling, so I opened up the bottom of the cowl. (a suggestion from my LHS)

Where should I go from here?

Thanks

Jeff Boyd 2

If I can just add to this (as I don't want to post again for the SAME problem . . please don't delete me :-).

Mine has had the same problem from new . . not every flight, but MORE than enough. The motor suddenly quits at about half tank. This can even be with the throttle open say 1/2 to 3/4. Virtually wrote off one model (rebuilt it).

It's not a cooling issue as I have mine fitted on a profile, and it's never 'hot' to touch . . and it's not tuning, as I have run mine every where from perfect needle setting to backed off slightly rich (i.e. bring high end needle to max revs, then back it off to drop 3 or 400rpm), with the low needle adjusted from slightly lean on the bottom, to rich (slowing quickly at idle with a burbling transition) . . and it still happens.

I have tried different plugs, replaced fuel lines twice, still does it.

It runs beautifully on the ground. Starts easy, idles smoothly, transitions cleanly, power is nice and smooth, it runs very quietly . . then BAM . . dead stick. FRUSTRATING :-(

One thing I noticed though . . it always seems to dead stick with the piston at top dead centre . . i.e. the piston is at the top with the prop able to rock slightly back and forth. I am wondering whether it's a tolerance thing and at a certain temperature it 'nips' at TDC (as it is an ABC engine ??

I have a friend with one and his is fine . . no tuning issues . . set and forget.

I don't get it . .

Cheers, JB

Bax

My Feedback: (11)

When an engine quits a few minutes into a flight, it's almost always due to it going lean. The most common reason is called "fuel foaming". That means that air is being agitated into the fuel that's in the tank. Adding air to any fuel mixture makes it go lean. You need to make sure the fuel tank is as well-isolated from the engine's vibration as possible.

Another thing that causes quitting a few minutes into flight is a cracked fuel line where the flex tubing in the tank meets the hard tubing. The fuel level comes down to that point and then the engine starts sucking air as well as fuel. Again, the engine goes lean.

If all else fails, put the engine on a test stand with a new tank and new fuel line (flush out the new tank and fuel lines with absolutely-clean fuel BEFORE you start to use them). If the engine will run "all day" on the test stand, then it's not the engine that has a problem, but something in the engine/airframe/fuel system combination.

Jeff Boyd 2

Thanks Bax . . I will look at those things.

Cheers, JB

yaronr

Jeff,

The AX55 is the most disappointing engine I had , out of my over 20 glow engines and 35 years of RC flying.
I had the same experiences as you have.
Tried it all: changing fuel, glow plugs, props, even different airplanes. Took off the deflector, than the muffler baffle. Nothing helped.

Finally, I replaces the bearings, sealed the back plate and carb seating with a sealant, use a 11x6 prop and added 2% oil to my fuel.
Now it runs.
Not with the intended 3d airframe and the big 13" prop as I planed.
I do not trust it , yet.

This came after a fantastic one year of 3d flying with a 13x6 prop without any problem with the AX55.
I run it carefully with a lot of experience as you may expect from 35 extensive RC flying.
Once the dead sticks started, there was no relief until the major rebuild.
There was no sign of ware or tare, nor any slack. The engine was practically new with only 50 flights, before the problem started.
I suspect that there is some air leak issue in the engine.

I must say, that I have other OS engines and they all run perfectly for many years.
I know some other members in my club, that suffer the same problem,
While, some others have no problem with the AX55, (same as me, in the first year).

I think it is about time, OS take responsibility for the AX55 "mystery".
These "mishaps can happen, I expect more support from a top Japan maker as OS.

Bax,

I am a big fan of OS engines.
Currently I own 7 of them.
I have years of RC modeling and glow engine running experience.
This issue with the AX55 dieing is beyond simple tuning or fuel system problems.
It is not generated by external factor, as I had tried changing all.
And, Yes! it will run all day on the stand, but still quit after few minutes in the air.
Please save us the grief and frustration and look seriously into the AX55 problem.
We all prefere spend our time flying, rather than writing these letters.

I will appreciate your frank and sincere advice.

Thanks,
Yaron.

evanspa

Anyone ever find a solid fix for this deadstick problem with the 55AX? Luck of the draw when you buy these motors? Unsat.
I don't buy the "tunning" crap, there is definitely and issue with this motor or exhaust. Don't find the same issues with the 46AX.

Bax

My Feedback: (11)

First off, there is no "deadstick problem" with the O.S. Max .55AX engine. If your engine is quitting at odd times, we'd bet that it's not the engine, but something in the engine/airframe/fuel system/settings...in other words, something external. In almost all cases, we've seen that the setup is the major difficulty. A too-large propeller, a restrictive fuel system, a dirty fuel system, leaking fuel lines, bad cooling, and on and on. If the engine is not turning in the mid-12,000's when at full throttle on the ground, then you may have difficulties. Turning a big, 13-inch propeller is asking for problems. An APC 12.25 x 3.75 prop would be good for 3D, and possibly their 12 x 4 prop. You need to get something to allow the engine to turn up. Use a good-quality fuel with NO LESS than 18% oil content. The more castor in the oil, the better.

One thing to check: If the engine is on a test stand, and you can run it "all day" with no difficulties, then your problem is not the engine, but something to do with the installation in the model.

yaronr

Thanks Bax,

Appreciate your hard work and fast response.

I guess it is only a question of expectations.
I got used to a very robust design of OS engines.

Never I had that sort of sensitivity/instability in any of my model engines.

Definitely, the environment changes from the test stand and the flaying model.
It's just that I can not simulate a model in the air to tune the AX 55.

My conclusion is:
"This is it"
I should accept the AX 55 as it is -Far less than I expect from OS.

Yaron.

evanspa

Okay, good to know there is no "Deadstick Problem" with the 55AX.

Bax

My Feedback: (11)

The O.S. Max .55AX IS robust. It is no more difficult to get it set up than any other engine, either now or in the past. We'd not know what "expectations" would be. NO engine has ever been "set and forget", not even O.S. engines. Also, modern airframes tend to be very light because so many flyers seem to expect "3D"-type of performance. The light airframes just don't absorb engines' vibrations like more robust aiframes do.

We've had this type of "complaint" ever since we started servicing O.S. engines over 20 years ago...then, the engines were the .50 FSR, .61 FSR, and .90/.91 FSR engines. We'd get the same types of complaints then that we do now.

jordisr

I have an OS 55 AX for almost 3 years and it has been running very well until it started to quit in the air some weeks ago. I looked at everything, fuel tank, fuel lines, and it continued to quit. Then I just replaced it with an OS 46 AX and same fuel, fuel tank, fuel lines and even same glow plug, and no problems at all.
I tried again with the 55 replacing the glow plug and I could fly one weekend without problems, the following weekend it starting to quit again.
But this weekend it has been impossible to fly, the engine quits on the ground. I tried different glow plugs, but the same result, the engine quits when you retire the glow plug igniter.
There is one thing that I do not like and this is that the exhaust is very dark. Maybe the engine is worn out and it has lost compression?
Any ideas?
The only good thing for that is that my daughter has learnt to land dead stick.
Thanks and best regards
Jordi

fourmaki

My Feedback: (1)

Same here with new O.S. Max .55AX engine. 3 gallons through. Dead stick every time mostly from half throttle to full. Installed on board glow works fine now.

The only trouble now won't stop, barrel closes to stop then takes a good 30 seconds to stop. I know it now and start shut down as I taxi back to pits. I even put finger over carb still won't stop quickly. I know must be an air leak. Do I take off the back cover and seal better and carb to body O ring replace? internal carb leak? Only 3 months old.

Bax

My Feedback: (11)

OK. Time to close this thread. It's getting too long, and turning into a discussion. If INDIVIDUALS have specific questions, please post them in their own thread. This forum is for people to ask us for help and get answers. IT IS NOT A DISCUSSION FORUM.

Thank you.

Again, if an engine (ANY engine) quits after a few minutes, it's either going lean or overheating from another reason. You'll need to check the entire fuel system and the cooling system. Many cowled engines just don't get cooling because the airflow goes from the air inlet to the air outlet without passing through the engine's cooling fins. You may need to make baffles to get the air to pass through the fins.

Fuel systems are common locations for problems...air leaks, dirt in the system, bad connections, air agitated into the fuel by vibrations, and so forth. If you keep having dead sticks, then put the engine on a test stand and see what's going on. If it will run "all day" on a test stand, then there's nothing wrong with the engine, regardless of how it's performing in the airplane. The problem isn't the engine, but in the combination of the airframe/engine/mount/fuel system combination.