.45 MagnumPRO won't run at full throttle

by Keith
(Philly)

Hi, I have a .45 MagnumPRO glow 2-cycle engine. I got it very used.. it has been crashed at least once, but it seemed to run OK for a while.

Now, I can start it easily and it idles great, but when I increase the throttle it will only run up to about half throttle. When I go any further, either it dies completely or slows down a lot.

When it dies, it dies instantly. I tried moving the high-speed needle in and out quite a bit with almost no change.

Is it possible I'm super rich on the low-speed needle and it floods when I open the throttle?

Another possible clue: after running for even a short time i see a lot of fuel and oil dripping off of the outside of the muffler... seems like it's coming from around the muffler/engine mating surface?

Oh, this is mounted inverted in a Banshee.

Thanks for any advice before I just start turning needles with no plan!

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.45 MagnumPRO won't run at full throttle

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Nov 18, 2009
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tank position
by: Keith

Hi Keith,

Let me address your last question first.

When "tuning" an engine you are basically tweaking the fuel/air mixture going to the engine. As you are fully aware, if this ratio is not correct you will have problems.

Since glow engines (most of them at least) don't use fuel pumps, they rely on the mechanics of the engine to pull the fuel from the tank. If the center line of your tank is pretty much center with the carburetor then it probably doesn't make much difference what position the airplane is sitting when tuning.

But if your fuel tank is an inch below the carb, it will be an inch above the carb when upside down. This could be enough to mess up your tuning a little bit.

I would recommend tuning it the way you plan to fly it. But I can't imagine it would make a huge difference the other way around unless your tank is mounted way off center.

AS far as the exact RPM's that define low speed vs. transition vs. high speed, I'm not sure.

But I suggest working on the high end first. Get it to where it runs reliable at high speed, then come back and tweak the low speed.

Once you get it idling correctly, go back and readjust the high speed if necessary, then double check idle again.

It's like a viscous circle sometimes, but you always want to work on getting your high speed correct, then tweaking the low speed.

So yes, for the time you are adjusting the high end, ignore the low end. And vice versa. But they do affect one another so you have to keep adjusting them both separately until you get it lined out.

Some people like to get their glow engines to idle as slowly as possible. It definitely doe sound cool to hear a 4-stroke idling slow.

Personally, I adjust my throttle trim to idle as fast as possible, just under the point to where airplane begins to roll. Its much easier to adjust the low speed when then engine is running a bit faster.

I hope this helps. Let us know how it turns out or if you have any more questions.

Thanks,

Matt

That being said, I would recommend tuning the engine the engine in the position it will be flying.

I am not sure if it's that big of a deal. But if your

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Nov 18, 2009
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Submitted by: Keith

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Hi Keith, Let me address your last question first. When "tuning" an engine you are basically tweaking the fuel/air mixture going to the engine. As you are fully aware, if this ratio is not correct you will have problems. Since glow engines (most of them at least) don't use fuel pumps, they rely on the mechanics of the engine to pull the fuel from the tank. If the center line of your tank is pretty much center with the carburetor then it probably doesn't make much difference what position the airplane is sitting when tuning. But if your fuel tank is an inch below the carb, it will be an inch above the carb when upside down. This could be enough to mess up your tuning a little bit. I would recommend tuning it the way you plan to fly it. But I can't imagine it would make a huge difference the other way around unless your tank is mounted way off center. AS far as the exact RPM's that define low speed vs. transition vs. high speed, I'm not sure. But I suggest working on the high end first. Get it to where it runs reliable at high speed, then come back and tweak the low speed. Once you get it idling correctly, go back and readjust the high speed if necessary, then double check idle again. It's like a viscous circle sometimes, but you always want to work on getting your high speed correct, then tweaking the low speed. So yes, for the time you are adjusting the high end, ignore the low end. And vice versa. But they do affect one another so you have to keep adjusting them both separately until you get it lined out. Some people like to get their glow engines to idle as slowly as possible. It definitely doe sound cool to hear a 4-stroke idling slow. Personally, I adjust my throttle trim to idle as fast as possible, just under the point to where airplane begins to roll. Its much easier to adjust the low speed when then engine is running a bit faster. I hope this helps. Let us know how it turns out or if you have any more questions. Thanks, Matt That being said, I would recommend tuning the engine the engine in the position it will be flying. I am not sure if it's that big of a deal. But if your

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Nov 18, 2009
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adjust upright, run inverted?
by: Keith

Oh, one other perplexing question (to me): the engine is mounted inverted in the airplane, but is impossible to adjust that way. So, I invert the airplane (engine now upright) to make adjustments and then upright the airplane (engine inverted) to see how I did. Is it OK to just adjust everything with the engine upright? When I invert the engine after adjusting everything, will I have new problems that need further adjustment?

Thanks,

Nov 18, 2009
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A few more questions
by: Keith

Thanks, matt. I'll try the pinch test. I guess I'm struggling because I've always run new engines before and I've never had to adjust the low-speed screw ever. With this older/used engine, the low-speed adjustment seems to need something but I'm unsure about when the high-speed and low-speed adjustments matter.

Maybe you could offer some advice on 2 specific questions?
The engine idles at ~3000rpm, and it dies between 6000-7000rpm. At that speed, is the high-speed needle even doing anything yet? Is it in the transition area, or is the low-speed adjustment the one to work on?

At idle, does the high-speed needle even do anything? Should I completely ignore the high-speed needle when adjusting the idle and then ignore the low-speed adjustment above 10,000rpm?

Thanks for the help. I'll try out a few things this weekend and let you know how I make out!

Nov 18, 2009
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sounds kind of rich
by: Matt

Hi Keith,

It's really hard to say, but it sound like the high end needle may be a little rich.

If the high end was too lean the engine would just die abruptly. If it's rich, it will stumble/slow down before dying.

Have you tried the pinch test?

Run the throttle up just shy of the point where it normally quits and try to pinch test to see how it reacts.

If the RPM's increase significantly then the high end is too rich.

It really concerns me that you say moving the high end does nothing...

If moving the high end doesn't change how the engine reacts to the pinch test then you may have something wrong with your high end needles.