OS .25 and .46 problems
 

I have an OS .25 and a .46 LA that I am having some trouble with. I am very new, so even if it is obvious to you, I would appreciate it if you mention it. When I run them up, they become very hot, but when I richen them up it doesn't seem to make any difference. I have checked the fuel lines for junk or cracks, but I have found none. Does anyone have any suggestions?
I would appreciate any help.

Thanks,

Matthew

RE: OS .25 and .46 problems
 

What kind of fuel are you running ? If you have the wrong fuel, and too big
a prop....the engine will overheat. [:o]

FBD.

RE: OS .25 and .46 problems
 

I'm running Omega 5% on both. The .46 has a 10x6 prop, and the .25 has a 9x4.
Thanks

RE: OS .25 and .46 problems
 

Do they have remote needle valves ? The fuel and props are good. ;)

RE: OS .25 and .46 problems
 

Just to be sure, do you have the mufflers on them, and are you running a line from the nipple on the muffler to the fuel tank? This pressurizes the fuel in the tank.

RE: OS .25 and .46 problems
 

I have a muffler on both engines, with the pressurization line running to the fuel tank. The .46 has a remote needle valve, and the .25 does not.
Thanks

RE: OS .25 and .46 problems
 

Doing good so far, prop sizes are in the right range and mufflers and pressure are being used. The next thing I'm wondering is how you define running hot? All engines run "hot". Is your assessment of hot based on a comparison to other engines, or just that they feel hot when you're finished running them?

You said richening the engine doesn't make any difference. Is it possible that you've got the needle set too rich? How many turns out is the needle? Have you tried setting it leaner?

Typically what you should do is start with the manufacturer's suggested setting. For most engines, this will be too rich. Once you get the engine running you want to gradually lean it until it's on the slightly rich side of peak RPMs. The way to determine this setting is to gradually screw in the needle. The engine will get faster and faster, but then will begin to slow. When it begins to slow, you've gone past the peak setting. Immediately screw the needle back out through peak to the somewhat rich side.

Note, you should not set the engine so close to lean when you're breaking it in. Also, the setting I described above is not ready for flying, it's just for running the engine on the ground or on the bench. To confirm the high speed needle is set appropriate for flight, you need to hold the plane firmly with two hands and have someone else run the throttle up to full speed. Once it's at a steady speed, point the nose of the plane straight up. If the engine slows down, it's too lean. Lower it and set it richer and try again. If the engine stays at about the same speed, it's also too lean. If the engine speeds up a little and holds this speed, it's probably about right. If it speeds up significantly, it can probably be set a bit leaner.

While doing the above, you should NEVER try to adjust the needle while you're holding the plane in the air. You also should never run the engine up, or adjust the needle while you are in front of, or beside, the prop arc. Engine adjustments should ONLY be made while behind the engine and with the airplane firmly secured.

RE: OS .25 and .46 problems
 

When I say hot, I mean I can't hold my fingers on the engine at all because it is too hot. I heard that you should be able to hold your hand on the enigne without it burning you, or it's too hot. Thanks for the tips.

RE: OS .25 and .46 problems
 

Wrong information about holding your fingers on the engine.

You will definitely NOT be able to hold your fingers on ANY part of the cylinder assembly after the engine has run at full throttle for a few seconds.

If your engine can hold maintain the same rpm at full throttle for 2 minutes on the ground it is definitely not overheating. If you have a good "ear" you will hear the engine note change as it starts to overheat. The first sign is a "harder exhaust note and the second a drop in rpm.

Get the guy at your field who turns up, never seems to have trouble starting his engines and does not fiddle with the needle and flies all day without dead sticks, to show yow hao to set it.

RE: OS .25 and .46 problems
 

I agree with this. I never (intentionally) use the sizzling finger test to determine if my engine is running right.