Cant get any spark out of my mag. Just finished a job and drove it home. Got there and found my fuel tower bleeder had come open. Fuel everywhere on my machine. Next day I move it into an area to clean it up. Washed. it down all over (hadn't been cleaned in a while). Just used high pressure water hose. Went to start it and guess what. Pony spins (12 Volt elect ) great. Wont start. Has been starting fine. Check for spark. NONE. Hmm?   water in mag? open mag and sure enough moisture. Stick paper towel in it leave it open all night. Should start. This morning put cap back on still no spark. Go to basics. Put a screw driver on coil output tang and look for spark at coil output. None. That bypasses rotor. See sparking at points. ???  Pulled it and was going to tear it down to dry it. Can't get the rotor off. Cant see a retainer. Any help there? Any suggestions at all?

Hi OB,
if the points and innards appear dry then maybe disconnect the magneto kill switch and see what you get--if the switch has water in it it will likely be shorted to ground resulting in zero spark.
High Pressure washers and water in general should be kept away from electrical devices.
Cheers,
Eddie B.

Dont even have a kill switch or wire on the mag. Use the fuel shut off. It does put out enough spark to shock me but not enough to jump a .010 gap. Coil?

Check resistance of the secondary coil winding. Should be approximately 6200 ohms.
Also try cleaning/filing the points.

OK 6300 ohms resistance for an instant then a open circuit. Ordering new coil.  BUT< Still need help. Is my rotor just stuck tight Or is there some kind of a keeper on the shaft? Dont want to pry to hard on it. Already tried screw driver from each side prying up, but don't want to break anything. Parts book illustration does not show a keeper. Going to hit it with liquid wrench and let it soak. 

There is no retainer or keeper used. Just a snug male/female fit of the mounting shaft that is about 1/2" long. Has to come straight out as it is keyed so that it does not rotate in the gear coupling. Good candidate for rust if some lube or antiseize is not used.

Hi oldbeek,
To change the coil you do not have to remove the rotor, just remove the gear the housing (opposite end to the cap) and undo the 2 screwsthat hold it in , these may be hard to undo, for mine I heated the housing around the screws (had to do several times) with a low heat and eventually they came loose. On installation I put antiseze on the screws before installation, now it works great.

Regards

Hi Team,
courtesy of Old Croak Magneto is a link to a Bosch MJK Service Manual.

oldcroak.com/mjk-ed-a-b-c-service-manual/

Hope this helps.
Cheers,
Eddie B.

I figured that out. not worrying  about the rotor any more. I am starting to realize I have been through this all before. This same mag gave me fits about 3 years ago. I remember having it on a magneto test bench and it magically started sparking perfectly, so I put it back on. Ordered a new coil this time. Thanks for all your help.

While working on the mag problem, I spun the engine over and the mag drive gear got moved. Now I have a timing problem. Got the mag back on close. The pony runs ok till I engage the engine. Pony just slows down and sometimes quits even after I remove the load. Think I have it off time and retarded one tooth. Any thoughts? Advance one tooth and it would back fire through carb I think. Only been doing this stuff for 65 years but my brain is failing me.