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Magnum 91 Sluggish

Old 12-07-2001, 02:39 AM
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Default Magnum 91 Sluggish

I have a Magnum 91 mounted on one of my planes. Yesterday I noticed that when I accelerated to full throttle there was a HUGE delay at times.

Engine runs great, cranks great. No deadsticks (for engine problems - loose props don't count).

Any idea on what can cause a delayed full throttle? I plan on re-checking my throttle linkage and make sure it is not binding, it was kinda tight when I set it up.
Old 12-09-2001, 04:19 PM
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Default Mag 91

Sounds like a idle mixture problem. After peaking rpm and backing off 300 to 400 rpm with high speed needle, return engine to idle closing throttle to lowest position where engine continues to run. Disconnect the fuel tubing from carb, and observe what happens. If the engine speeds up before quiting, then the idle mixture is too rich. If the engine speed decreases and then quits the mixture is too lean. From idle quickly open up all the way, if the engine hesitates, mixture is too rich. Might not hurt to throw in another new glow plug also, as this can contribute to a poor running engine. Hope this helps you get your Mag 91 running strong again.
Old 12-09-2001, 09:35 PM
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Default Magnum 91 Sluggish

Went out flying today. A little cold, but it was fun.

It was indeed the idel mixture. It ran fine on the ground, and seemed fine to me. But we did richen it up some and it is running great now. Was just a little bit to lean.


Thanks,
Randy
Old 12-12-2001, 10:12 PM
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Default magnum engines

I have a 120 and noticed that after a gallon of fuel, my engine lost a lot of power - once I adjusted the rocker valves everything was good. Except for my YS120, I have never had to adjust the valves on any 4 stroke.

I really like this engine though, it always starts on the first flip and has never quit in the air.
Old 12-15-2001, 12:55 PM
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Default Magnum 91 Sluggish

I am not sure what Glow Plug yuo are using. If its not an OS type F then try one. A fellow flyer was having idle and transition problems with his magnom 80 at our field. I gave him an OS F plug to try. All problems gone, the engine ran perfectly.
Old 12-18-2001, 04:35 AM
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Default magnum .91

The OS plug can't be beat........ except for price. I have had little or no problem with the Fox miracle plug. I only have Magnum 4 strokes...... and the Miracle plug really does a good job for about 2.50 . Hope this helps....... I am retired and broke fixed income...... wish I knew how to fix it.
Old 12-18-2001, 11:35 PM
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Default Magnum 91 Sluggish

Right now my engine is running smoothly

Wish I could say the same for my flying

Anyway, I am running a OS plug also. Costs a little more but they are better. I also had an OS 91 engine. I switched engines one day and no one could tell the difference in how the plane was flying. I know I will get a war going but for the money savings the Magnums can hold thier own....


Fire away!

Randy

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