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I have you a&p guys a magneto question..

J

jordanrv6a

Member
ok.. my left magneto stop working., I took it apart and set the e-gap.. it seem the points had something in them keeping them from breaking., but I got a good spark going again after cleaning..timed it bAck internally. and stabed it bAck back in..pulled the pin out.. and timed it at 25% befor top dead center..time ing seemed great.. cranked it up. and the mags checked out .. but the left mag dropped 75 rpm.. and the right 50., well that seemed close enough to normal., but the left mag witch is the one I pulled off . would NOT run up to 2100rpms like the right mag.. it acted like it wasn't getting enough fuel and it got worse.. finally got were it wasn't checking out at 1500rpms., do yall think its the coil is not putting out enough spark! because it is Putting out at spark at low rpm.. but finally gets worse and worse and would die when after about 20 minutes of running engine.. . thTs what my a&p said. just want y'all's a Pinion! when it gets hotter you think the coil is going out the spark would get weaker until the mag stop working?
 
Check your spark plugs and wires.

There is a possibility that if the timing is perfect like you say that the spark is not making it to one or more of the plugs.
 
RV6_flyer said:
Check your spark plugs and wires.

There is a possibility that if the timing is perfect like you say that the spark is not making it to one or more of the plugs.
Click to expand...

My vote is fouled plugs too. Also easy to check - along with resistance.
 
Mag

Did you snap the impulse and then rotate the mag backwards to engage the Pin??? If not you have it timed to the engine wrong.
 
magneto is slick mag

ok.. cleaned plugs.. checked e-gap.. timed internally.. I put the number one cylinder on the compression and let the mag snap.. pulled it back to before 25% mark and timed the magneto at 25% before top dead center.. the mags ran up and checked out at 1600 rpms at a 75rpm drop on left mag and 50 on right.. but when I tried to run up the left magneto it would not go past 1800rpms without acting like I was pulling the mixture.. you pull the throttle back and it would run.. but finally it wouldn't run hardly any.. when I check the mag with a spark plug wire on the ground off the plane it we throw a spark quarter of a inch away.another question.. my right mag is timed before 25% of the mark. but I set the left that I put on at 25% before top dead center.??? what yall think.. coil??i pulled all my spark plug wires back away from any ground.. thanks guys .. keep talking!
 
magnetos are new with about 250 hours or less on them

the points are breaking every time.. set e-gap.. and timed the plastic gears right.. I get a good spark.. but man after running it on the left magneto for 10 minutes it want hardly run on it.. what would change other that a weak spark from coil.. ?? I know the points aren't moveing and time ing isn't changeing.. but when I take it off and put a plug on it and snap it threw or hold it .. it puts out a jolt of fire but it's not like I can't stand it. but it does jump across a plug. about a 1/2 of a inch.mmmmmmmi I think its loosening fire when it spins faster.. guessing
 
This is just a shot in the dark, but it's what happened to me....

Check the points. They are attached to the spring steel arm via a rivet-looking method. Mine was actually 'floating' on the arm - not secured solidly to the spring steel arm. The points floated on their attachment and gave varying results operationally. This was after the 500 hour 'inspection' service by a reputable shop that had changed these points. The mag ran fine before the 500 hour service, and either ran fine, rough, or not at all after the service.

Easy to check. See if your points look good and don't move.
 
A friend of mine had a slightly similar problem. His engine would start fine when it was cold but was hard or impossible to start when it was hot. Also sometimes got a little rough at cruise power. On top of what you described, do you have a hot start problem ? If you do then I would think you have his same problem, he replaced the coils in both mags and everything is fine now. Seems like they would work when cold but broke down with heat.
 
Tempest coil

If you do replace the coil, I had to once, but it is now my spare so I haven't used it yet.

I was told by a Mag repair shop that the Tempest brand coil was cheaper and better, so that is what I ordered. He said that a plug with a bad resistance will cause a slick coil to go bad over time but the Tempest coil would not. I'm just telling you what I was told, I can't say one way or another.
Aircraft Spruce sales them:
http://www.aircraftspruce.com/pages/ep/magnetos_16300/replaceslickmag.php

I think they are about $70 cheaper.
 
Points bad...

Scott,
I had the exact same problem ( probably the same shop ) same 500 hr. check. It acted "funny" when timing that mag, sometimes Ok, then it was "off".
Anyway, I think this is a Slick service bulletin. Brought it back to him, fixed, works great.
John
 
thanks guys..

I'm going with the coil first .. I just didn't think the coil would change spRk one minute and stop and start again. guess it's not putting out enough spRk at high rpms. thank yall lots
 
You can check it

You can test the coil with a multimeter. I had one that was fine cold but once up to operating temp it shorted out. Very evident with the multimeter but I had to test it hot. Good luck. Let us know.
 
Coil Check...

Charlie, This is a learning experience for me. How do you use a multimeter to check a magneto coil for being shorted out?
John
 
time ing question

are both magnetos supposed to be times at 25 before top dead center of so my right mag is off it lights up before it gets to the 25 mark.. but I'm setting the left on 25 before top dead center.,
 
weird mag issue

Listen to Walt! the capacitor is probably breaking down and is an important part of the system. If you are intent on changing the coil change the cap first and try it again.
Tyler
A&P, GROL
 
Easy

You use an ohm meter to check the resistance of the primary and secondary windings. I think the primary should be around .5 ohms and the secondary about 15K ohms. If someone has better numbers please speak up. You are looking for opens or shorts in the secondary winding mostly and these usually show up when the coil is hot (140 degrees). Here is a pic of someone testing a secondary coil Good luck.
 
it was the coil

just wanted to thank everyone for there input and on my question.. great guys on here.. but it was the coil .. just wasn't putting out enough fire!. and as it warmed up it got worse. changed it and ., it's like new again.. but boy did I learn a lot about magnetos, Timeing internaly and Timeing it back to the engine. it can get hair pulling but when you finally get it. and understand it all.. it sure feels good. thanks again
 
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