Magnum 52 Engine Will Not Stay Tuned

by Chuck
(Boonville Mo)

I have a Magnum .52 and I have been having trouble with the engine not holding the settings. I get it running like a champ the take it to the field just to find out that it is back to old games of not wanting to transition well.


Or it will run great on the ground, once in the air however it runs good for a bit the without warning dies. This motor is on an Edge 540 and that plane is not easy to dead stick and it is getting old fast. Any help would be great.

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A few things to try
by: rcdude07

Did you replace your glow plug? A bad glow plug can cause this issue.

How old is the engine? I have an Supre Tigre 45 that is 15 years old and inside is worn now, so motor doesn't stay running.

Have you adjusted the low end? Sometimes the low end will need tweaking.

Do you point the plane nose up and give full throttle as well as transition the throttle? Doing this will help simulate how the engine will lean out in flight.

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Tuning problems
by: Chuck

It is a new engine, and the plug has been replaced a few times. They were not all bad I just replaced them to eliminate that as a problem. I have tuned both the high needle and low needle. I get it tuned up and running great at home, then at the field it will not transition or just dies. I have a friend hold my plane nose up for me when I am running it up. That is why I have turned to other R/C friends for help. I can not figure this engine out.

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Broken in?
by: rcdude07

Did you break the engine in on a stand? If it's not broken in properly it can be problematic. Are you using a tachometer or just your ear to tune?

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low speed needle
by: Anonymous

The 52 magnum is a tricky engine to tune. I think the problem is the low speed needle. There are some .52 that will tune well and others do not. There is a variation in the low speed needle shapes I found out by reading other posts. For example, my needle was a 3 degree half angle taper 5 mm long, another owner had a 2.5 degree half angle that was only 4 mm long. He modified his low speed needle taper and got it running perfectly. I did the same and got my engine to run really well. I had to change the angle to about 2 degrees half angle.

The Magnum 52 engine has special porting that shoots the incoming fuel mixture directly at the glow plug. If the engine is just a little bit out of tune (rich side) then the fuel will snuff out the glow plug. This usually happens at mid throttle somewhere. With he high taper on the factory needle, the engine can be tuned at idle well and at full thottle well but leaves midrange rich. If you adjust the low or high to account for the rich midrange it screws up the other points on the throttle.

There might be another fix for this problem but after a few dead sticks, I modified my low speed needle and all is working good now.

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