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Magnum XL 28

Old 08-08-2021, 10:56 AM
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4dogspete
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Default Magnum XL 28

I may have roasted my Magnum XL 28 glow motor.
This is a fairly old motor - bought a few years ago at an auction. Mounted in a Great Planes Big Stik 20
Tunde fairly well - was running a 9 x 4 Scimitar prop - just didn't seem to have much oomph.
Fuel - Wildcat 15%
switched to a Master Airscrew 9 x 5. Last 2 flights the back half of the muffler came loose.
Today while flying - motor just quit - was performing very well.
Landed OK then touched motor - really hot!
Now almost no compression.
Was it running too lean?
Anyone know if there are piston-cylinder parts?
Any other thoughts???
Old 08-11-2021, 08:16 AM
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jaka54
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Hi!
As you have the engine in a high winged trainer airplane I would suggest to use ...
1. A bigger prop , like a APC 10x5 or 11x4.
2. Less nitro, I use 5% nitro fuel for all my engines and have done so for the last 45 years flying at sea level.
If you fly at an higher altitude , say 500m-1000m or above, using 15% nitro could be better.
3. Use fuel containing Castor oil, 20% is the old stand by that all engines like.
4. Set the engine richer before taking off.And remember to hold the nose up when setting the engine!
5. Use a not to large tank! 6oz is the maximum and use exhaust pressure.

Last edited by jaka54; 08-11-2021 at 08:20 AM.
Old 08-11-2021, 09:12 AM
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4dogspete
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Default Magnum 28

Thanks for your comments - will give them a try!!!
Old 08-11-2021, 12:35 PM
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jaka54
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Hi again!
Forgot to say ...use either an OS 8 or Enya 3-4 glow plug.
Old 08-14-2021, 06:35 AM
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aspeed
 
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Just thought I would mention that my early Magnum .28 which was made in Taiwan (Thunder Tiger) had a tight crank seal. I had to polish the crank to make it looser. Then it ran gangbusters.. It was surging and the case was hot, really bad runner before. I have a lot of old T Tigers with tight or sloppy crank fits that give bad runs. We run 8-6s on our .25 size schnuerle motors and they seem quite happy.in the 16,000+ rpm range. Maybe the motor was for sale because of the tight crank fit giving problems, and hopefully the lack of compression was just from that cause. It caused me a lot of grief before I fingered that one out. The bottom of the case was very hot after only running a short time.

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