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Mag Question

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Brian Schmidt

07-15-2000 20:20:41




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I don't know much about mags. Can someone explain how they work to me.

I looked at a Cub today that had a mag. The guy had a separate coil wired in. Does this mean there is something wrong with the mag. I didn't think a mag needed a separate coil. I don't understand what is triggering the coil or why it would run this way. I thought you just ran a switched wire to them and that was it.




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Phil Auten (TX)

07-17-2000 05:18:25




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 Re: Mag Question in reply to Brian Schmidt, 07-15-2000 20:20:41  
Brian,
It is also possible that the mag has been converted to a distributor ignition. I have one tractor that has been converted and it works, but of course is not original. Either type of ignition will work, the choice is up to you which one you want to keep.
Here's a brief rundown on how both types of ignitions work:
The mag has a spring loaded impulse coupling built in to assist with starting. It's function is to make the spark hotter at cranking speeds and it is no longer employed once the engine is running. It will make an audible click as the engine is rotated by hand. The impulse trips at the exact time needed to cause the magnets in the bottom of the mag to rotate quickly past the small coil of wire that is the primary side of the ignition circuit. The current induced into the primary is then interrupted by the points opening. This causes the magnetic field arount the primary coil to collapse immediately. The collapsing magnetic field induces a current in the secondary winding of the cignition coil which creates the spark voltage for the plug.
The battery ignition works in a similar way, but the points carry current from the battery through the primary side of the ignition coil, building up a magnetic field until the points open, causing the rapid collapse of the magnetic field which induces the spark voltage in the secondary winding of the ignition coil.
The battery ignition is quite a bit simpler which explains the conversion of many mags to battery ignition, or their replacement with a battery ignition distributor.

Hope this is helpful,
Phil

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RB

07-16-2000 08:19:59




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 Re: Mag Question in reply to Brian Schmidt, 07-15-2000 20:20:41  
Ther is a good article in the archives somewhere on how a mag works.Redfan has it pretty nailed down.On the mag youre talking about the moving parts are still working.But most likely the coil windings inside are bad.Instead of replaceing the 50 buck or so windings the owner used a 6 or 12 volt coil,wired the neg. side of the coil to the condesor and it worked.How do I know,Ive done it several times myself to get me through a situsation where i couldnt wait on coil winding.I have done it on several different types of mags as well.Just recently I did it on a buddys F-12 to see if the tractor would at least run.

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Brian Schmidt

07-16-2000 20:28:12




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 Re: Re: Mag Question in reply to RB, 07-16-2000 08:19:59  
Thanks both of you for the help.

Do either of you know what these coil windings run $$$. And are they available from IH or would I need to find another source.

Thanks



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Redfan

07-17-2000 01:45:56




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 Re: Re: Re: Mag Question in reply to Brian Schmidt, 07-16-2000 20:28:12  
Sorry, can't help much there. I was lucky to be able to get one for an H4 mag., from my local garage that was an IH dealer many years ago. Sat on the shelf for about 40 yrs so he gave it to me. I'm not posting from the States, but a name that comes up a lot on this board is Ken Updike whose phone No. appears in a later post above. He would be able help you I'm sure and I hope he doesn't mind me mentioning his name.Regards, Redfan.

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Redfan

07-16-2000 01:14:39




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 Re: Mag Question in reply to Brian Schmidt, 07-15-2000 20:20:41  
An expert I'm not, but here goes. In distributor type ignition the current comes from the battery to the coil, where it is boosted in voltage a whole heap, till the points open and then the high voltage in the coil collapses and is taken to the spark plugs where it goes to work. In a Mag. situation the current is generated by the Mag. itself, then boosted in the coil before travelling to the plugs. In the Cub you mentioned, for it to have an extra coil attached would indicate the coil in the Mag. is dead, but the rest of the Maggy is still working. Clear as mud, I'll bet.Regards, Redfan.

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