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Magnum 40 GP

Old 07-07-2002, 03:03 AM
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le fou
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Default Magnum 40 GP

A firend gave me a Magum 40 GP. I flew with it today. When I adjust the needle valve on the ground, everything seems to be great. When I flew the airplane, the engine doesn't give any power, it is like it is on the rich side.... I don't understand what's going on. As well, does somebody know if the Magnum can have a low idle without stalling ?

Thanks
Old 07-07-2002, 04:53 AM
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w8ye
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Default Magnum 40 GP

I would think that you have peaked the engine out as fast as it will go and engines always get a little leaner when in flight compared to the ground and the engine is going too lean.

You should adjust the high speed needle for maximum rpm and then open it back up a couple hundred rpm. (3 or 4 clicks)

The Magnum 40 GP is an excellent first engine. This one is actually a Thunder Tiger engine. It is no longer offered by Magnum or Thunder Tiger.

The idle is an air bleed. You screw it out for leaner and screw it in for richer. Normally they are real easy to set.

Your glow plug or fuel may not be the best in the world?

good luck,

Jim
Old 07-07-2002, 05:30 PM
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le fou
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Default Magnum 40 GP

My carburator is not air bleed. It is the two needle setting type. I am sure it is a Magnum 40 GP. Is something wrong?
Old 07-07-2002, 08:41 PM
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dennis
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Default Magnum 40 GP

the Magnum GP40 or TTGP 40 has an airbleed carb. More importantly it requires a break in. It is not strictly a but and fly even though it is an abc it requires about 5 runs on a slightly rich setting with a cool off after every flight. Another thing is to have fuel with a known oil content 2/3% castor wont' hurt either. do not over prop it and it should run fine
Old 08-08-2021, 11:33 AM
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Dear all
i habe 2 Magnum GP40 left from my stock and I installed them into a new Harmony from ripmax.

i dont get the engines running well.
therefor I re-installed them to put them on a test bench.
Im using Graupner 16% Methanol fuel which Is pretty nice on all my other (OS, Rossi and ST) engines.

unfortunately I disassembled them before running as the were stucked for about 10 years in a box.

I assume that I dont set the Nozzle right.

i will add a picture later on to explain it better.
Old 08-08-2021, 11:41 AM
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This is the GAP Im asking for
Old 08-08-2021, 07:48 PM
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A. J. Clark
 
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I would think the nozzle should be centered in the carburetor barrel. Open the throttle and you should be able to see where the nozzle is.
Old 08-08-2021, 10:36 PM
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This is the maximum I can put it into. If I put it more into the carburetor, the throttle doesnt move easily anymore.

Old 08-09-2021, 05:18 AM
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A. J. Clark
 
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The location of the nozzle looks ok to me. What are the symptoms of the engine running bad?
Old 08-09-2021, 06:37 AM
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First of all thank you!

The Air bleed screw dont have any impact of the engines behavior.
i have to open it fully to run the engine.
Im using a Medium Rossi R3 glow.
With a Hot one, it runs better.
but dont steady on idle.

Once the high needle is set (and one or two clicks means engine off!) I go to idle.
Then after 30 seconds or a minute I set full throttle and the engine struggles to get high position again. It takes up to 4 seconds to reach high position.

Idle shuts the engine off after some seconds of being steady.

If I try to work with the air bleed screw, the engine doesnt make any difference in his behavior.

Starting by hand is not working.

This is the first engine which are not running.
compared to old Webra Speed 40 or just 40.

Due to the fact that the model is a 2 engine one, Im afraid of using these engines in this model.

But maybe somebody has a good advise what to check.
Old 08-09-2021, 07:43 AM
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If it's to lean or to rich the air bleed screw may not have much effect on idle. I would take a piece of clean fuel tube connect it to the fuel inlet and blow into it to see if the needle passage is open. Then open the high speed needle 1 and 3/4 turn should be enough to run good a little on the rich side.
Old 08-09-2021, 09:42 AM
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Adjust the high speed needle first then the idle. Might have to go back to the speed for a small adjustment.
Old 08-09-2021, 10:24 AM
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Originally Posted by A. J. Clark View Post
Adjust the high speed needle first then the idle. Might have to go back to the speed for a small adjustment.
This is what Ive done on both engines. But they are not idling good and reliable.

therefor I adjusted now the nozzle to be centered. Maybe I will try it on Wednesday again by reporting.
Old 08-10-2021, 05:57 AM
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Hi!
The nozzle should be screwed in more! So it is in the center! of the intake opening. Why is this not possible?! The fuel nozze cannot interfere with the throttle drum in any way and if it does something is wrong and remove the drum and check it out.The low speed needle should be centered in the hole! The engine will throttle just perfect in this position.
Second the fuel: 16% oil is a bit low! Try 20% castor oil fuel instead and at least 5% nitro.
Prop: 10x6 or 11x6 preferable Graupner G-sonic, RAM; or APC.
Glow plug : OS 8 or Enya 3

Last edited by jaka54; 08-10-2021 at 05:59 AM.
Old 08-10-2021, 06:16 AM
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Originally Posted by jaka54 View Post
Hi!
The nozzle should be screwed in more! So it is in the center! of the intake opening. Why is this not possible?! The fuel nozze cannot interfere with the throttle drum in any way and if it does something is wrong and remove the drum and check it out.The low speed needle should be centered in the hole! The engine will throttle just perfect in this position.
Second the fuel: 16% oil is a bit low! Try 20% castor oil fuel instead and at least 5% nitro.
Prop: 10x6 or 11x6 preferable Graupner G-sonic, RAM; or APC.
Glow plug : OS 8 or Enya 3
hi
Im using 16% nitro.

it is impossible to screw it more to the center. It will block the drum. On both engines. I can re-check.
one engine was out of the box and it cames with the fuel inlet in the first quarter of the drum.
strange.

I will re-try by posting pictures.
Old 08-10-2021, 07:14 AM
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Hi!
Centering the fuel inlet nozzle isn't that important as the engine will be happy with the position you have now.
I would run the engine on 5% nitro as it runs just perfect with that percentage of nitro. 16% is just a waste of money and could be a part of the problem you have with the engine. Too much nitro and the engine will pre detonate and will be hard to, or nearly impossible to set.
Old 08-14-2021, 06:57 AM
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Don't forget that the idle screw of an air bleed carb is the opposite of a regular carb. Turning it in will make the idle richer not lean. Some guys take a pin and put it in the bleed hole and snug up the screw till it just touches the pin. This is about half way covering the hole and a good place to start. Then after that the normal setting procedure of getting the idle mixture is followed. More than 1 turn could be too much from that starting setting. Too rich, and the motor will sputter and spit fuel from the carb. when full throttle is given Too lean will likely just die quickly. The air bleed carbs are always a bit rougher than the newer two needle carbs but work pretty good. Oh, and the full throttle setting has nothing to do with the idle mixture.
Old 08-14-2021, 10:24 AM
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Originally Posted by aspeed View Post
Don't forget that the idle screw of an air bleed carb is the opposite of a regular carb. Turning it in will make the idle richer not lean. Some guys take a pin and put it in the bleed hole and snug up the screw till it just touches the pin. This is about half way covering the hole and a good place to start. Then after that the normal setting procedure of getting the idle mixture is followed. More than 1 turn could be too much from that starting setting. Too rich, and the motor will sputter and spit fuel from the carb. when full throttle is given Too lean will likely just die quickly. The air bleed carbs are always a bit rougher than the newer two needle carbs but work pretty good. Oh, and the full throttle setting has nothing to do with the idle mixture.
thank you.

today I had the chance to put both engines on the test bench.
Ive adjusted the air bleed screw in order that the hole is half closed.
then Ive forwarded the nozzle to the middle of the carb inlet.

the engines are running fine now on the test bench. After idling for 1 minute they quickly respond. I will put them in my plane by flying them now :-)
Old 08-14-2021, 11:16 AM
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Maybe I can save you some time and frustration.
30 years ago I had this engine (Magnum GP 40) and some friends also, and frankly, they're garbage.
We all had the same problems, get it running right on the ground, take off and dead stick.
Of coarse we wrecked a few planes doing this, not fun!
I believe they were defective, air leaks most likely, some of my friends returned them to the hobby shop.
I did get mine to run consistently on 30% nitro but at to great a cost.
I wouldn't use one again, to many other good reliable engines to be had.
That's my experience for what it's worth.

Scott

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