magneto is dead?

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masterx1234

New Member
May 7, 2009
51
0
0
grayson Kentucky
my bike is just now on its 4th tank of gas and the darn magneto has quit, and yes ive tested everything els, tried new coil: still no spark, tried new spark plug: still no spark, so its all down to the magneto, so why would it just burn out so quickly? and also do they sell these type of coils at the hardware store? or will i have to buy another one online?
 

biknut

Well-Known Member
Sep 28, 2010
6,631
409
83
Dallas
I don't think you can get one anywhere except from an online store, unless you live close to Pirate Cycle.
 

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
Before you trash it, check the black wire where it attaches to the magneto.
It should be soldered to a ring terminal that is fitted underneath the head of the top right magneto mounting screw.
Some are not soldered at all, rather the ring terminal is merely crimped to the wire. This is a poor electrical connection. It needs to be soldered. It is easiest to replace the ring terminal with a new one but you can clean up the stock one with some scraping and a little patience. It needs to be very clean for the solder to adhere properly.
Also the ring terminals are known to have been covered in varnish by the factory after crimping. This too is bad as the varnish will act as an insulator.

The last thing to check is the center ground connection for the magneto windings. This is a short, thin wire coming out of the windings and is soldered to the metal magneto frame right next to the top left mounting screw. These are known to be cold soldered, where the factory worker does not get the wire hot enough to allow the solder to adhere properly to it. They create the solder puddle on the magneto frame and without even cleaning the red insulating varnish off of the coil wire, stick the wire into the solder puddle and hold it there until the solder cools and solidifies. The wire's varnish coating creates contaminates in the solder bond and that coupled with a cold solder bond results in a very poor connection.
 
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msrfan

Well-Known Member
Sep 17, 2010
1,808
120
63
Southern California
GearNut has the answer. I was about to trash the coil on one of my bikes and then read a post telling of the poor quality of the windings and solder joints. It mentioned a hair fine wire just under the wrapping that sometimes breaks. I peeled it back and saw that was my problem. I soldered it back together and it worked fine.
 

masterx1234

New Member
May 7, 2009
51
0
0
grayson Kentucky
well i did what you said, i re-soldered brand new wires to the coil, wired it back up and still nothing, and its not the coil or spark plug, i put a tester right where the wires are soldered to the coil and its not reading anything, so it looks like ill have to buy another coil
 

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
I did not mean to re-solder all the wires, just inspect the coil's center ground and black wire ring terminal, and re solder if necessary. It sounds like you went for the "Full Nelson" and did everything you could to save the mag. I commend you for your efforts!
I am sorry to hear that the fix was not so simple. Hopefully a brand new mag will fix it for you.
 

MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,741
1,211
113
CA
It may be a mute point now, but FYI, on a Briggs engine magneto I found the stiff wire that is used to go to the engine kill switch, low tension, it is very brittle with age. I cracked it right to the point within the epoxy where it comes out of the magneto.

My fix was to use a crummy old tip on a solder pencil to melt/burn away some epoxy, just enough to get a way of soldering high voltage flexible wire. I scraped the wire I exposed with an exacto knife to get clean of burnt epoxy. After I used a good tinned solder tip and soldered more wire, I used high temp red RTV and that became a massive strain relief when potted over a few inches of the wire and the magneto. Motor runs and trying to get another magneto for the engine that is out of support life, not a problem.

BTW the yellow wire going to the points under the flywheel also broke after I already use sealant on the points cover. I just used some heat shrink over the soldered extension wire to fix. This wire directly connects to the other previously way more brittle low tension wire. I soldered them together outside of the point cover and heat shrinked them as well. Then this is my low tension kill switch wire.

Measure Twice
 

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MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,741
1,211
113
CA
It may be a mute point now, but FYI, on a Briggs engine magneto I found the stiff wire that is used to go to the engine kill switch, low tension, it is very brittle with age. I cracked it right to the point within the epoxy where it comes out of the magneto.

My fix was to use a crummy old tip on a solder pencil to melt/burn away some epoxy, just enough to get a way of soldering high voltage flexible wire. I scraped the wire I exposed with an exacto knife to get clean of burnt epoxy. After I used a good tinned solder tip and soldered more wire, I used high temp red RTV and that became a massive strain relief when potted over a few inches of the wire and the magneto. Motor runs and trying to get another magneto for the engine that is out of support life, not a problem.

BTW the yellow wire going to the points under the flywheel also broke after I already use sealant on the points cover. I just used some heat shrink over the soldered extension wire to fix. This wire directly connects to the other previously way more brittle low tension wire. I soldered them together outside of the point cover and heat shrinked them as well. Then this is my low tension kill switch wire.

Measure Twice
Just one more picture to clarify

Measure Twice
 

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