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Right slick mag is losing 400 rpm after post flight mag check

Saber25

Well Known Member
Ok Guys,
I’ve had slick mags on my RV4 for 25 years and never encountered any problems. Earlier this year I acquired a Pitts S1S with a pumped 0-360 and tight cowl. I’m posting here since we have a large knowledgeable crowd and someone might have experienced the following problem. After a hard session of acro my right mag has a drop off of 300-400 RPM when I do the shutdown mag check. The left one is still good at 125 RPM, the same drop for both mags when I first go out in the morning. It would seem to me the tight cowl and 10.5-1 pistons are creating enough heat to somehow affect the right mag. I never had this on my RV4 which also gets flown quite hard. I have checked the fine wire plugs and also changed from top to bottom and the resistance on the plugs is all within parameters. The mag internals getting hot is my guess. Any other answers?
 
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Dave,

I think you are right, that seems to be the consensus on another forum. Now I have some work ahead :)
 
mag

Hans,

Are you going to fix the mag yourself. If you take it apart, check for evidence of arcing ( carbon tracks ) If you need help let me know. Check the points, egap, rotor gear, cap , carbon brush etc. relube the bearing bar
People bash these mags but they are very simple units and very reliable if properly maintained. If you don't have a manual I can tell you how to get one from Champion directly for free.

cm
 
One of my Slicks experienced a slow failure of the oil seal. As the inside of the mag got wetter, drop increased. It was only 200 hours since overhaul.
 
Thanks Chris,

Today I installed a new blast tube better positioned than was currently on the firewall. One more flight right over the airfield to let her warm up and see if the lack of proper cooling could have caused the problem. I'll post results.
 
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