H mag diagnosis (update)

[BruceS]

Ok, I'll have one more go round on this mag discussion. Thanks to all who responded and tried to figure out what I was trying to say. Here are the facts after looking at this thing again: 1) the rotor is in the correct position when mag trips 2) I did not mess with the little gears that drive the rotor; all I did was to change points, condenser, and coil. The slotted driver on the tractor is in correct position. 3) I have gone "by the book" (IT manual) in timing mag (p.42) The mag appears to take too long to wind up and passes timing marks on pulley before it snaps. That's about the best I can do on explanation. Thanks for listening.

 

[rhtx55]

It states in the service manual to flush the mag trip coupling mechanism with solvent (diesel should work fine) occasionally to remove any gummed up accumulated oil.
Once free & working properly to re-lubricate with 20 wt oil.

 

[Bob]

Set the engine to TDC, loosen the mag mounting bolts and rotate the mag top away from the block 'til the impulse trips.

If you have reached the end of the slots and it hasn't tripped, the governor shaft is not where it's supposed to be, or the impulse trip lug is worn, damaged, or somehow else not doing it's job properly.

http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html
Page 54

 

[Nebraska Cowman]

Your impulse may well be gummed up and not working properly but that will not change where it trips. The impulse stop is a fixed peg. It can't move. I agree with Bobs assessment that the drive gear may be off a tooth but if it ran fine before and you did not have the drive off it should run again. UNLESS...... You said it stopped running? Could have something failed mechanically inside like the cam gear? Just a thought.

 

[[email protected]]

Try this... The model may be different, but worked perfect on my H.

http://www.youtube.com/watch?v=QqucExhxXdE&feature=youtube_gdata_player

 

[Roger l hall]

Ok I'm going to try this !!! Set # 1 piston on compression stroke (tdc) next take the mag to fire on # 1 trip the mag (don't let it spinto no 2) while holding it in that position by the rotar insert the Mag into the slot and put a bolt in it on the top tight enough to still be able to twist it. Now rotate the mag top as close to the engine as it will go Now turn the motor until # 1comes back up to compression tdc ( stop do not go past tdc). Next go to the mag and get a good grip on it. Turn the top away from the motor (slowly ) until it trips (stop there ). Tighten the mag down there. It should be in fire position#1 tdc ( rotar will not stop on #1 when it trips) you are in time. Put it back together and fire it up,,!,, Roger [email protected]

 

[Tom Fleming]

Howard, very good point. I bought an A that had a battery ignition on it. PO had rebuilt the engine, so it ran strong. I wanted a magneto on it. I put a fresh, rebuilt mag on it and nothing. I could not get it timed right. I spent almost a week scratching my head why I couldnt get it timed right.

Finally, I took the governor off, and found that the PO had missed the timing marks on the governor gear by 6 teeth. Once I had the governor gear timed correctly, all things worked like a champ. started first crank, and timed perfectly.

If your engine was running and then suddenly stopped, there could be a failure in the cam/mag timing gear train. easy enough to pull the governor and see if the timing marks are lined up............