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Magneto ...bad part????

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loveshisallis

02-09-2008 18:07:11




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I have taken apart my FM J magneto putting in new points and condenser. When I put it completley back togther, it didn"t fire at the plugs. So, I took off the top cap(two screws) and put a length of wire fron the conductor to a plug, grounding the other end.I carefully checked both the internal timing of the mag and its timign to the engine. All checks out fine. Thus, for every impulse I got, I got a nice fat spark on the plug. So why is it that I can"t get any spark to the plugs when I put the rotor cap back on?
I have new J-5 plugs with copper wires , and they check out.
Is it a bad cap or what?

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loveshisallis

02-12-2008 15:54:52




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 Got it fixed! Magneto ...bad part???? in reply to loveshisallis, 02-09-2008 18:07:11  
Thanks to all who helped me out on this thread.
I repaired the following:
Replace and dressed points, new condenser from napa, tightened the conductor rod that contacts the copper tab on coil, and cleaned the rotor.
NOW I have that HOT, Fat spark that jumps 3/8 of an inch.
Thanks Much



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sjh

02-10-2008 15:20:18




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 Re: Magneto ...bad part???? in reply to loveshisallis, 02-09-2008 18:07:11  
Is there a brass rod sticking out of the cap. This would go into the conducter hole. It should be about 1/2" long.



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Clay in MI

02-10-2008 08:47:09




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 Re: Magneto ...bad part???? in reply to loveshisallis, 02-09-2008 18:07:11  
The rotor should be pointing to the timing boss (the little plastic bump inside the magneto cover - the one with 4 screws) when the impulse snaps for the #1 cylinder.
I'm far from an expert, but I have a mag on the bench right now and could try to talk you through it this evening. Email me your phone # if you want.

(I tried to write out the steps but it didn't even make sense to me.)



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loveshisallis

02-10-2008 06:31:41




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 Re: Magneto ...bad part???? in reply to loveshisallis, 02-09-2008 18:07:11  
When the impulse SNAPS on number one compression, WHERE exacty does that rotor point? Does it land directly on number one spot, or where?

I had no luck in timing it by the internal marks, so I lined it up on the engine fire mark.

Thanks



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Kentb of SWMO

02-09-2008 18:34:10




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 Re: Magneto ...bad part???? in reply to loveshisallis, 02-09-2008 18:07:11  
Your cap could also have drawn some moisture. Take a 100 watt flood light bulb in a reflector socket and mount near the mag to heat and evaporate the moisture. While the mag is drying-out go to the parts store and buy a can of clear top coat paint, Clear acrylic paint. Leave the light on the mag over night. Remove the light, let the mag cool a little, 15 minute , and then spray the cap all over with the top coat paint. This will seal the cap. I have seen old mag caps that were a whiteish/gray that drawed moisture BAD turn shiney Black. After this treatment I have seen mag out in the rain start and run.

Kent

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old

02-09-2008 18:19:48




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 Re: Magneto ...bad part???? in reply to loveshisallis, 02-09-2008 18:07:11  
Cap could have a crack in it. Heres a way to check it for cracks and it also cleans it at the same time. Take some starter fluid and spray the cap inside and out. Shake it off and then let it dry on its own. After is has dried look it over. If you see any lines in it any where then you have a cracked cap. Those lines are the cracks and if cracked because of moisture it will short out the sprak

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loveshisallis

02-09-2008 19:35:41




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 Re: Magneto ...bad part???? in reply to old, 02-09-2008 18:19:48  
When you say cap, do mean the main body that is held with four screws? Or and top with the two screws in it?

Thanks for the help !



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old

02-09-2008 20:51:19




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 Re: Magneto ...bad part???? in reply to loveshisallis, 02-09-2008 19:35:41  
Either one or both can cause that problem. Or even a cracked rotor will cause that.



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loveshisallis

02-10-2008 06:32:32




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 Re: Magneto ...bad part???? in reply to old, 02-09-2008 20:51:19  
When the impulse SNAPS on number one compression, WHERE exacty does that rotor point? Does it land directly on number one spot, or where?

I had no luck in timing it by the internal marks, so I lined it up on the engine fire mark.

Thanks



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old

02-10-2008 06:48:47




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 Re: Magneto ...bad part???? in reply to loveshisallis, 02-10-2008 06:32:32  
Didn't I send you the manual for that mag?? If I did it explains all that in that manual.



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loveshisallis

02-10-2008 07:04:24




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 Re: Magneto ...bad part???? in reply to old, 02-10-2008 06:48:47  
Right, I got the manual, problem is, I can't make out ANY kind of a mark on the steel gear.Even with a good light and a magnifying glass, so I need help in getting the interanl timing right.



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old

02-10-2008 07:14:52




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 Re: Magneto ...bad part???? in reply to loveshisallis, 02-10-2008 07:04:24  
You get #1 to TDC and install the mag. You have a 50-50 chance of having it correct and if the first time you don't turn the mug 180 and put it back on. Or siwthc the wires around.



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