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

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?

Magneto
 

What brand of magneto & how many hours since new?

Welcome to VAF! The official "greeter" will be along directly to make it official! :p

Check Egap again. Sounds weak.

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.

Bad capacitor can cause the same symtoms.

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.

This was the cause of a recent mag failure with similar symptoms for me.

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!