Mag Problem on H'

WE have an 1940 "H' with the most trouble free Mag ever until now. Tractor ran when parked in open shed and always started easy but now spark is weak and almost nonexistant. I cleaned up points and coil wire& port but when snapping it over there is a tiny spark. The Condenser has white powdery stuff on it but haven't really got to it. Where do I start???
 
Condensers do fail. That powder is probably corrosion either on the outside causing a disconnect, or inside causing failure. Go there. Jim
 
Is the weak spark at the plugs or from the wire that goes from the coil cover to the cap? If strong here, then your cap or rotor is dirty or worn, or you have bad wires. If still weak here then it is either points, condensor or coil.

There's a pretty good "wrenching with rachel" video out there on how to rebuild a magneto. I have used it with pretty good success. janicholson's suggestion to start with the most obvious problem is probably your best bet.
 
sometimes the only way to clean the points is to remove them and use a motor driven wire steel wheel. I bench test the mag using a battery powered drill to run it and I can go slow and turn at different speeds with each wire hooked to a grounded plug. That way I can check to see if I have good spark at all plugs and at different speeds so when I install it I know it will work. Have you soaked the impulse end in diesel fuel and then blowed it out so its clean. Manual told us to do that once a yr. I like my mags they are trouble free.
 

Magneto coils go bad, as well.

I've replaced two H-4 coils this summer for customers' mags that suddenly had a weak (but consistent) spark.

To the O.P., copy the link below and paste it into your browser to view the original OH Blue Ribbon Service Manual for magnetos.

http://farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html
 
I think that Condenser could be it. Lots of corrosion in there like someone dumped a bunch of powder in the cavity. For the moment I had a parts "c" tractor and transferred the distributor to the "H" and it is running again. A little more wireing but that I can understand?? Cleddy
 

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