OS50 XXrich@1/4 stick
03-04-2003, 09:37 PM
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OS50 XXrich@1/4 stick
Last year I had severe problems with my OS50. It has an extremely rich point at 1/4 stick, and the engine really wants to kill itself during spin-up. I dont want these problems again this year! I have standard muffler with raptor50, gear ratio 8.5.
Some people say this is a known problem, but others seem very happy with their OS50. So I wonder, do these people just never use 1/4 stick, do I have a bad OS50 (batch with bad needles or so?) or is there a known trick for this (eg, leaning out the low end needle, or whatever)???
PS I put the same question on RR, but here is a special OS-engine thread that is not on RR.
Some people say this is a known problem, but others seem very happy with their OS50. So I wonder, do these people just never use 1/4 stick, do I have a bad OS50 (batch with bad needles or so?) or is there a known trick for this (eg, leaning out the low end needle, or whatever)???
PS I put the same question on RR, but here is a special OS-engine thread that is not on RR.
03-06-2003, 04:54 PM
#2
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OS50 XXrich@1/4 stick
w.pasman,
We've not heard of any particular problems in the O.S. Max .50 SX-H engine.
Usually, model engine carburetors are not linear, and tend to exhibit richness in the midrange. The mixture in the midrange is determined to a large extent by the idle mixture setting.
If the engine is set with a very low idle, then the engine can richen up a relatively large amount as the throttle's increased. Once the engine starts to get near 1/2 or more throttle, then the setting of the high-speed needle tends to rule the mixture.
Generally, if the midrange is too rich, leaning the idle mixture a bit and possibly increasing the idle RPM a bit will help the problem.
Another thing to check is the fuel system. Is the fuel tank depressurizing when the throttle is reduced? If a check valve is used between the muffler and the fuel tank, then the tank will be holding too much pressure when the throttle is reduced, and the engine will trend rich.
This might also tend to happen if the fuel tank's a bit high in relation to the carburetor and the tank's full. Does the problem tend to become alleviated when the fuel tank level is below one-half? That would be a key.
One final check: If the engine will run perfectly when it's on a test stand with a propeller, then you'll be absolutely sure that it's not all an engine problem, but a result of the engine/airframe/fuel system combination that's contributing to the difficulty. Tracking down a problem can then be quite a task.
We've not heard of any particular problems in the O.S. Max .50 SX-H engine.
Usually, model engine carburetors are not linear, and tend to exhibit richness in the midrange. The mixture in the midrange is determined to a large extent by the idle mixture setting.
If the engine is set with a very low idle, then the engine can richen up a relatively large amount as the throttle's increased. Once the engine starts to get near 1/2 or more throttle, then the setting of the high-speed needle tends to rule the mixture.
Generally, if the midrange is too rich, leaning the idle mixture a bit and possibly increasing the idle RPM a bit will help the problem.
Another thing to check is the fuel system. Is the fuel tank depressurizing when the throttle is reduced? If a check valve is used between the muffler and the fuel tank, then the tank will be holding too much pressure when the throttle is reduced, and the engine will trend rich.
This might also tend to happen if the fuel tank's a bit high in relation to the carburetor and the tank's full. Does the problem tend to become alleviated when the fuel tank level is below one-half? That would be a key.
One final check: If the engine will run perfectly when it's on a test stand with a propeller, then you'll be absolutely sure that it's not all an engine problem, but a result of the engine/airframe/fuel system combination that's contributing to the difficulty. Tracking down a problem can then be quite a task.
03-07-2003, 07:01 PM
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OS50 XXrich@1/4 stick
Bax,
Thanks for the suggestions!
> We've not heard of any particular problems in the
> O.S. Max .50 SX-H engine.
Maybe you should check it on RR, there are quite a lot of people with this problem.
Increasing the idle RPM together with leaning out the idle? Mmm I never tried that I think, I will try thanks.
I dont have a valve, and the problem occurs right after starting, during spinup. I think the pressure is still building up at that moment.
The tank is at standard height for raptor, just below carb I think when full. I have a header tank in the middle of the main tank, so even lower (this should not matter anyway)
About the propellor check: which propellor should I use?
Thanks for the suggestions!
> We've not heard of any particular problems in the
> O.S. Max .50 SX-H engine.
Maybe you should check it on RR, there are quite a lot of people with this problem.
Increasing the idle RPM together with leaning out the idle? Mmm I never tried that I think, I will try thanks.
I dont have a valve, and the problem occurs right after starting, during spinup. I think the pressure is still building up at that moment.
The tank is at standard height for raptor, just below carb I think when full. I have a header tank in the middle of the main tank, so even lower (this should not matter anyway)
About the propellor check: which propellor should I use?
