Can anyone suggest a good source for repair of my American Bosch magneto, preferably the eastern side of the USA, but not necessarly in the east.  Thank you!  Elton

 

Thanks Neil, but you know, when you pay over $100 for a cap and nearly that for a rotor, you've spent a lot of money and maybe not got to the problem anyway. So maybe before messing too much, I 'll just send it off and get it properly repaired with a guarantee. It might be cheaper in the long run. More opinions are welcome. Before I put it on the pony engine, I spun the mag with my hand and it made a nice blue spark. On the engine it will not do anything. I suspect an internal short. The previous owner complained about the pony motor being hard to start and running poorly. Maybe it was a pony mag problem all along. Elton

Electric start, hasn't run since overhauled. New pistons, bearings, etc. I will check to see if it turns, but it should. It is an American Bosch. I have adjusted the points and the plug gaps. the wires are new and so are the plugs. Input is welcome.

I bought a J series D2 not running, as it turned out the mag on the pony was not set up for ccw rotation, we had to change the cam in the mag to change it to a ccw rotation. The former owner died but there was evidence he had recently installed the wrong mag.

Put new steel core wires in and new plugs, I had a TD 18 one time with a new rebuilt mag that would throw blue fire on the bench but wouldn’t fire on the tractor. I put wires and plugs and it fired right off run like a champ!! 17afarmer

heres a couple of tips,
NEVER CLEAN A MAG WITH PETROL(GASOLINE) THEY CAN EXPLODE OR CATCH FIRE EVEN DAYS LATER USE METHYLATED SPIRIT OR ELECTRICAL CONTACT CLEANER WHICH IS A CLEAN SOLVENT LET DRY IN A WARM PLACE AND WELL VENTILATED.
mags earth through the body so the mating surface needs to be spotlessly clean of dust, grease, paint, rust etc. it doesn't have to be perfectly smooth but not rough. dress the surfaces if needed and clean with contact cleaner or metho

to help the mag work at its best coat the surfaces with 2B pencil blow off the excess and bolt up try it again its surprising the difference it can make also file and adjust the points so they are spot on all these little things can make a big difference.

just because a plug fires out of a cyl doesnt mean it will fire when under compression fit new plugs its a cheap fix. ive had this happen with stationary engines fit a new plug away it went.

now if the pencil trick doesnt work the mag may need rebuilding or at least re-magnetising. ask if they vacuum impregnate their coils with resin if they dont go else where if they say what's that go elsewhere vacuum impregnating gets the resin right into the middle of the coil winding sealing it from moisture properly yes it takes longer and costs a bit more due to labour but you get a job that lasts better. try the magneto guys in the uk they can do mags for just about anything. just because a bakelite cap is craked doesnt mean you need a new one its possible to repair them.

blue spark on the bench but not on the motor that tells me its not getting good return path. or there is current leakage some where it shouldnt be.

replace the plug wires, the wire to the kill switch, soak kill switch in "shellite" put it in a plastic jar with lid and shake well to clean crud out of it, the switch might be faulty inside and not working as it should be and giving a intermittent ground when it shouldnt do anything when in run position (the switch grounds the mag to stop the pilot motor) (any good hardware or parts store should have shellite also used as a fuel for camp lights and stoves was a shell oil company product)

clean the mating surfaces try the pencil trick fit new spark plugs clean the plug threads with a spark plug thread tap. note most plugs are metric thread thank you Mr Bosch.
try it with the kill switch disconnected make sure that the end of the wire cant touch anything or it can stop it working if this makes a difference then the kill switch is the problem

if no improvement then yes the mag may need rebuild. if you send it in dont ask for a test get it rebuilt saves head aches later.