neuroza

Hi!
I have two MAGNUM GP40 engine that I use with 0% nitro (20% castol, 80% methanol).
The problem is that both engine just die on high RPM, and when the engine become warm it's impossible to start again...
I'm goin mad because i really try to adjust the neddle and the air bleed but it can't be done...

Is it possible that the reason is because I use 0%???

If I go to 10% or 15% will this solve the problem???

Thanks!

longdan

What plug are you using? Try a hotter one. Or try taking a shim out from under the head.

neuroza

Yes! I put a hot plug and take out the shim under the head. And now just start better, but on high RPM still die, and when it's warm can't start.
The engine die even when I put the nose up or down...

I have one maybe stupid question , but what do I have to do with the third out from fuel tank??? One goes to carburetor, one goes to muffler, and the third???


Thanks!

Motorboy

Difficult to start engine while the engine are warm means there are not enough compression cause hot sleeve and cold piston by fresh fuel. Let it cool before restart the engine.

Close the third fuel hose. The fuel tank must be pressurized by exhaustmuffler to give engine fuel.

neuroza

Yes I close the third opening on carburetor.

Then the only problem is that the engine can't go on full... When I put the gas to maximum the engine go down, then I have to put the gas to middle, etc...
Like that there is a point that can not be overridden...

Motorboy

Too much oil or no oil out of exhaust?

Too much oil=lean out fuel and vice versa.

Better to run the engine with a bit rich than leaned fuel mix and the engine must not be cold cause too rich fuelmix.

Adjust the engine to max rpm then turn back 1/2-3/8.

YUKONFLYR

Neuroza - Sounds to me like you have an air leak problem. If you are running a hot plug and have removed a shim then 0% nitro should not be a problem.

I have had engines that die when you go to full throttle and the high speed needle is adjusted properly. Turned out to be the glow plug.

Also what is your weather like? Cold...... I have had engines that are next to impossible to transition when the outside temp drops down to close to freezing. If you are trying to run your plane outside at like 4 deg C , with 0 nitro......well that is tough. Methanol is cold to begin with and with no nitro for heat is tougher.

If you can warm up your plane in your car first, or garage then quickly start it at full throttle and adjust the HS needle, Does it still run? If it does then its just cold and when you reduce the throttle setting the engine will get cold in about 15 seconds and will not rev up again and Die....That is if it is cold

It could also be the installation..If you have no luck with the above I would pull the engine and mount on a test stand to confirm the problem. Could be leaning out due to a pin hole in the feed line, or in the tank line to the clunk, vibration in fuel causing it to lean out.

I have run engines indoors in an industrial environment ( repair shop ) with lots of ventallation!!!! When it is cold outside, Never run indoors enclosed....I know you already know that

Let us know how you make out.

Richard

neuroza

I use an new glow plug (Try to change it but is the same...)
The weather in my place is pretty warmly (10 to 15 celz.)
I think that maybe can be some air linking problem... This is because I don't have the silicone fuel line but some kind of plastic gum fuel line that doesn't fit perfectly (it's little bit bigger)... I will try to find whats the problem...

One question:
Is there some trick to raise the compression in fuel tank???

Thanks!

YUKONFLYR

Neuroza - To help keep pressure in the fuel tank you can use a one way check valve on the exhaust pressure line to keep the tank pressure up. I like the YS check vlaves and OS has good ones as well.

If your fuel line is too large that could be where the air is getting in. Also if you do use a check valve make sure all your fuel connections are good and tight. I have had a Sullivan Flex tank enlarge like a blowfish under pressure when using a check valve, something to think about, maybe check on a test stand

Richard

neuroza

I'm so desperate, today I try again with new silicone fuel line, but it's allways the same F _ _ _ _ _ G problem...
I'm really try everything imaginable, and just doesn't want to work.
The engine start really easy, but when I try to go to full gas the engine just die...

Tommorow i'm goin to buy some fuel with 10% or 15% to give my last try, if this will not work i'm goin to some sanatorium coz i'm goin maaaaaaaaddddddd!!!!!!!!![:@][:@][:@][:@][:@]

So I have another question... Is it possible that my high needle need to be open more that 9 or 10 turns?!?!???!

Motorboy

No, it is not normal, the hi speed needle will be between 1.5 and 4 turns depent on weather and brands of model engines.

neuroza

Can please somebody tell me what is the first position of air bleed and hi needle to start the adjustment...

YUKONFLYR

neuroza, have you tried to start it at full throttle?

The air bleed screw if turned in cuts off the air for the low speed / idle circut in effect making the fuel mixture richer. So this is really not a problem to full throttle running.

The High speed needle controls the mixture for hi speed running. If your needle valve has to be out so far out like 8 to 10 turns I would be questioning if there is enough muffler pressure.

I ran a NovaRossi 50 CF last night with just a basic header, no pipe. headers do not offer much back pressure and I had the needle screwed out so far that it actually came out of the carburator[X(]

I then installed the pipe and the needle valve only needed to be screwed out about 2.5 - 3 turns. I do not know what the spec is for this engine, however if you start it at full throttle it si easy to find the proper needle tune. I was running it on a test stand.

I think that the only way you will get to the bottom of your engine problems is to remove it and install it on a test stand with a known good fuel system that you can watch when running the engine. I never run a engine on a plane that has not been run on a test stand. It is too hard to diagnose problems without having a proper baseline to start from.

Richard

downunder

I seem to recall that a few people had problems with the Magnum carb where the fuel nipple wasn't drilled correctly and that ended up limiting the fuel flow rather than the needle. With any engine you should be able to open the needle valve at full throttle to get it so rich it'll eventually just stop. Usually this is only one or two turns from the best setting.

neuroza

FINALLY!!!
I find the problem... The needle valve have some little gum gasket, that was missing... Yes the guy from e-bay sold me a new air bleed carburetor for magnum GP40. But he "forget" to tell me that this gum was missing, AND that the needle valve was slightly different (I think is for O.S. Carburetor #3A 35-40FP).
The needle fits but miss out some air, and with this different needle the little gum can not be mounted...
Anyway I replace the needle and put this gum gasket and now the engine ROCK!!!

Thanks for all the help...[&:]