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Engine won't keep running.

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Engine won't keep running.

Old 07-03-2021, 03:26 PM
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Thumbs down Engine won't keep running.

A friend at the field has a OS 40 engine on his trainer. Its a 40 size Kadet high wing trainer with a 60" wing span. He flew the plane earlier with no engine problems. When he went to fly it again, he refueled the plane and started the engine. No problems You could hold the nose up then down and the engine kept on running. But when his flight trainer carried the plane with the engine running to the runway and sat it down the engine stopped running. This happened 6 or 7 times. They changed the glow plug numerous times. Pulled the glow fuel tank and found that the fuel chunk was rubbing against the back of the inside of the tank. So we shorted the chunk glow fuel pickup line 3/16". Replaced all the glow fuels lines including the glow fuel pickup line as well. Put it all back together. Filled the tank and started the engine. The engine sounded a lot better. Nose up, Nose down it kept running. Walked over to the runway and put the plane and and it quick running again. So gentlemen what seams to be the problem. We are thinking it's the carburetor or the engine itself.
Old 07-03-2021, 07:59 PM
A. J. Clark
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Have you tried with the idle a little richer?
Old 07-03-2021, 08:51 PM
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Do the "pinch test" when at idle. Use whatever tool or fingers that will safely pinch closed the fuel line going to the carb. If it continues to run, but picks up speed before dyeing, the idle mixture is too rich. If it dies quickly and abruptly, it is too lean. You should be able to get several seconds of run, without it picking up rpm before it dies. A bit of going too rich, then backing it down, will get you to the ideal point.
I'm guessing it currently is a bit too rich, and the time at idle to get it out to the runway was longer than the in the pits testing - so it built up too much fuel, and stalled.
You can also use this method to test the top end needle setting, with point-it-up-and-down as the final verification. I'd then back off a click or two to the rich side, just to be conservative.
Old 07-04-2021, 05:38 AM
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Seems the engine is afraid of flying
Old 07-04-2021, 06:07 AM
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It’s very possible that the clunk rubbing could have flaked off some of the plastic from inside the tank that got into the filter or carburetor.
Old 07-04-2021, 08:42 AM
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OS engines are dead proof (like all other glow engines)! So...if the engine is not working properly you have done something wrong.
First the tank.Tank size is important as a too large tank will make the fuel setting more difficult (engine will have more difficult to cope with varying fuel pressure) so you should use a 240cc (8 oz tank) at most!
Tank placement: It is vital that the tank is mounted correctly. That means that the tank center should be placed in line with the carb intake orifice when the plane its horizontal! And also the tank as close to the engine as possible.
Glow plug: OS 8 or Enya 3...but there are others that work fine too, like Rossi 3 or Nova Rossi 4.
Glow fuel: OS engines run fine on nearly all percentages of fuel, 0-10 % nitro and 20% oil work fine and the rest methanol. I run 5% nitro in all my glow engines.
Old 07-04-2021, 10:36 AM
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Default Which OS 40 engine model is it?

I would agree with post #2 and #5 as my first step to get this adjusted. I would richen the idle air bleed screw 1/8 of a turn at a time between test runs to see what you get IF THIS IS A FP or LA air bleed carb. See photo.
If the OS 40 is a FSR, SF, or FX, then it's not an air bleed carb and your low speed is made richer by turning the screw counter clockwise to richen it. If it flames out after making these adjustments, then you likely have a blockage in the line, but I wouldn't expect it to even run if that was the case. It wouldn't hurt to remove the needle to clear it out, some tank debris could be blocking it.
How many seasons are on this engine? What model engine is it? Filter all fuel going into the tank. Don't use a filter on board, they usually are too restrictive.

Finally, you could also remove the bolts to the head on these engines and inspect the liner. The nickel liner can peel and give you running problems as well. ​​​​​​ OS is not dead proof. All depends on what abuse it's endured in it's history. I often buy second hand engines and always deal with problems they gave up on troubleshooting.

Last edited by J330; 07-04-2021 at 10:48 AM.
Old 07-04-2021, 03:18 PM
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Also, check that all bolts are tight - front, rear, head and that the carb is firmly seated compressing the o-ring. Little leaks can be bedeviling, but usually make the engine very erratic, and not consistently badly behaved like reported.
But, an easy thing to check. Just don't use your "Hulk" strength on them, as they can be easily stripped.

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