OS 46LA engine stops when throttle is fully open

by Vivek
(INDIA)

I have OS 46LA engine. Fuel mixing : 75% methanol,20% oil, 5% Nitro.

I have new OS 46LA engine and I need to break in and set the high speed needle at a good position.
But when I try to start the engine, initially engine starts at low RPM with 1 and 1/2 high speed needle valve opened and 1/3 throttle opened.

Then I gradually start opening the throttle. Engine RPM is increases up to 85% throttle open but after that around 90-95% throttle open the engine stops.

So I never get a chance to start the engine and run with fully open throttle and then set the high speed needle valve. Please provide me some of your experience to solve my problem,

Yet I have not burn a single tank of fuel yet.

I really appreciate your help,

Thanks,
Vivek

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OS 46LA engine stops when throttle is fully open

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Too Lean.
by: Michael from Oz

G'day.

One and a half turns open on the high speed needle is probably too lean. I would start with the needle about three turns open. This should allow the engine to run quite rich at full throttle.

Run a part of a tank through it then pinch the fuel line closed. (When it is running rich, you may need to leave the glow driver connected. This will not cause problems so long as it is running rich.)

When you pinch and hold the tube, the engine should speed up (run leaner) so once it does, release the tube and let the engine go back to running rich.

This is an easy way to give the engine a range of running conditions - rich and lean.

After a couple of tanks like this you can lean the high speed needle to the point where the engine just starts to run at a two stroke.

Like this it is slightly rich and you can fly it like this for several tanks and then slightly lean it for more power.

Never fly it absolutely at its peak - always richen it about a quarter of a turn and it will last forever.

Mike

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It works!
by: Anonymous

Hey Matt,
Thanks much for your comments.
It really works. It was happing as information you were provided me.
Now i can start my engine at high speed needle open about 2 and 1/2 turn open and it runs at low RPM and it will not stop when throttle is fully open. I burn 2-3 tanks at this rich settings. So now i can gradually close the high speed needle for subsequent flight but I will take care as you told me about lean settings.

Thanks,
Vivek

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Thank Michael
by: Matt

Hi Vivek,

I am glad you got your engine running properly!

However, you should thank Michael for the assistance, not me!

Happy flying!

Matt

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os91
by: Anonymous

hi mattt.i have a problem.when i throttle up my os91fx it quits.when i leaned a bit the low speed and i opened the high spedd i worked much better.i would like some straight forward answers because i hear a lot of solutions....please....

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Have you tired Michael 's advice?
by: Matt

Hi Vivek,

I think Michael's advice above is just about a straight as an answer as you're going to get.

Are you still having problems after trying the advice he has given? If so, more specifics of how your engine is behaving will help to answer you better.

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Engine Works Fine
by: Vivek

Hi Matt,
Yes! i follow Michael's instruction and engine works fine.

Actually Yet I have not get a chance to fly my 1st air craft due to bad weather. I start the engine with 3 turns open on the high speed needle. After that throttle is fully open and close the high speed needle about 1/2 turn. So it is not too lean.

I measure the RPM and Lowest RPM i can achieved is about 4000 and Max is 9800. I can increase but engine is very new so i do not want to run it on high RPM. So i think this setting should work well.

One thing i am wondering that according to the Company manual of OS 46LA engine, the practical RPM are 2000 to 15000. So how can i get this range, more prissily the lower range like 2000 RPM.

Should i increase the Nitro instead of 5% to 10% ?

I really welcome your suggestions and experience tips!

Thanks,
Vivek

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Same sort of problems
by: Jason T.

I'm having the same kind of problems as described by other people in here.

I'm running (attempting to run) a Tower Hobbies .75 with a 12X8 prop. 20 % nitro fuel, and OS glow plug.

I've run countless number of tanks of fuel through the engine and I cannot get it to go past 1/3 to 1/2 throttle with out dieing.

I've tried the high speed needle valve at several different settings and even the pinch test at different times.

As I sit here I'm running yet another tank through the engine with the needle 3 turns from close and the glow plug starter still on the plug. The engine just dropped in rpms for no reason and then went back up .

This is the second time that the engine has done this on this particular tank of fuel. Any help will be greatly appreciated.

It's now warm weather here And I've got the bug to get back into the air.

Now for a third time the engine is dropping in rpms without killing the engine completely.

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a little more info
by: Jason T.

I just ried the pinch test again and the engine tried to quit immediatley.

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Does it die immediately with the pinch test?
by: Matt

Hi Jason,

When you try the pinch test does the engine die right away? Or does it stumble, cough, and putter for a second first?

If it does immediately just a soon as you pinch the tubing then it's too lean. If it stumbles and carries on first then its probably too lean.

Focus on getting the high speed needle set first. Once it runs good at high speed then start concentrating on the low speed-transition.

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thanks
by: Jason T.

Thanks Matt, The engine dies as soon as I pinch the line. no coughing or anything. I'm already at 3 turns from close. surely I don't need to go with more. I can't get past the 1/3 to 1/2 open on the throttle so I'm not able to really set the needle.

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Open the high speed more
by: Matt

Hi Jason,

Sounds like your engine is definitely lean. These means it needs more fuel. So you need to open the high speed needle even more.

Just keep opening it further and further until the engine actually increases in RPMs when you pinch the fuel line.

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