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having problems with tuning of O.S .61FX

Old 11-17-2003, 03:17 AM
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Default having problems with tuning of O.S .61FX

Yesterday i was down my local airfeild tuning my engine as i was not getting enough power out of it.
i am using 10% fuel and have no plumbing problems.

When i brought the engine it was running fine with 15%.

I will try and tach it some time soon after i have fixed the cowl from the crash.
could anyone help me ?

Adam
Old 11-17-2003, 10:34 AM
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Default RE: having problems with tuning of O.S .61FX

You'll need to provide more information. Prop size and type, RPM you're running, how it's installed, type of fuel (brand and blend), and so on. There could be any number of things happening.
Old 11-17-2003, 01:16 PM
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Default RE: having problems with tuning of O.S .61FX

the engine is semi inverted in the plane and the fuel system works perfectly. the fuel tank may be very slightly above the carb but not enough to make it drip when standing on the tarmac. im using a 13x10 APC. the fuel i am using is a make i bought from a medium size model show (sandown to any one who lives in the UK) and that is 10%. ( i have had no problems with this fuel as i have used it in my irvine .53 and my thunder tiger .42)

(The previous owner was running on 15% which he used for his YS 91)

I am not sure on what RPM i am running as did not get a chance to tach it!

The engine is also fitted with a purple power pipe from [link=http://www.justengines.unseen.org/pipesjen.htm]www.justengines.unseen.org[/link]

Any other info needed. please write it down and i will get it asap.

Thanks

Adam
Old 11-19-2003, 08:24 AM
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Default RE: having problems with tuning of O.S .61FX

Bax have you had any ideas of what it could be???
Old 11-19-2003, 10:33 AM
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Default RE: having problems with tuning of O.S .61FX

OK...First off, we'd consider a 13 x 10 propeller to be much, too much propeller for the O.S. Max .61 FX engine. We normally run an 11 x 7-8, or 12 x 6-8 propeller. We look or a static RPM with the stock muffler of about 12,500 RPM or so. If the pipe's not tuned correctly, then the engine will also be down on possible power.

Even if the engine's being used for the old-style F3A aircraft, we'd use a 12 x 10 prop, but it would still be a bit much for the FX engine. The FX engines are more like the old FSR-series engines in the RPM they run best at. For larger propellers, such as you mention, you really need an engine propped for the lower RPM. The old Hanno was propped for a 12 x 12 prop at about 9,600 RPM when on the O.S. pipe. That's about the same RPM you'd get with a 13 x 10.

Get your .61 FX running closer to 12,000+ RPM, and you'll likely find its handling sweetens right up.
Old 11-19-2003, 11:03 AM
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Default RE: having problems with tuning of O.S .61FX

im still confused that when i test flew the aircraft it flew fine.. plenty of power and tons of torque. i have exactly the same set up as when i test flew it apart from the fuel. would it be wise running the engine on the floor without the cowl on to tune it up?? then fly it without the cowl , or should i use some 15% fuel.

Would i need to change the length of the tuned pipe if i changed the %of the nitro ?
Old 11-19-2003, 05:25 PM
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Default RE: having problems with tuning of O.S .61FX

If changing the fuel caused all of the problems, I'd change back. Did you completely reset the engine to the new fuel. Both high-speed and low-speed needles will need resetting. Is your fuel OK? Fuel with water contamination will cause the engine to run hot, and idle and accelerate poorly.

Try fresh fuel similar to what the engine used before your purchase and see if the problems persist or go away.
Old 11-20-2003, 03:14 AM
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Default RE: having problems with tuning of O.S .61FX

thanks Bax
I will try and use some 15% fuel and see what happenes. if it still runs poorly i will reset both needles and start afresh.

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