Internal Magneto problem?

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Moisstink

Moisstink

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Aug 2, 2013
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I have switched out two cdi's and a magneto. The last time the two were switched out the engine started and ran rough for a half mile and dead again. I found a little oil in the magneto area with metal shavings the first time I switched the magneto but after the half hour ride it looked fine but will not turn over.
This engine only has about two months on it and I have done everything except a full rebuild. What I am wondering in if something internal can cause magnetos to fail.
On the second magneto switch I extended the wiring to the cdi because of apehanger handle bars. I used a little thicker copper wire (can that lead to magneto failure?)
everything was soldered up with shrink tubing and looked good. Any ideas would be appreciated.
 
2door

2door

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Staff member
Sep 15, 2008
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Littleton, Colorado
When you say you "found a little oil in the magneto cover" that means to me that you might have a bad crankshaft seal behind the magneto rotor(magnet)
An oil soaked mag coil will not work. They can sometimes be cleaned and dried but replacement is usually necessary.

Using a larger guage wire from the mag to the CDI will not damage either component. Also there is nothing internal that would have any negative impact on the mag or CDI.
Oil, water or heavy vibration can cause premature failure. Have you checked your components with an ohm meter to determine which has failed?

The kill switch, button, is notorious for causing folks problems. We always suggest disconnecting it for testing but also strongly advise it be used if not found to be the problem. Having a way to shut down the engine in an emergency is invaluable.

Let us know what you find.

Tom
 
Moisstink

Moisstink

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The oil and metal shavings that I found after two months of riding was cleaned out before the new magneto was installed and I cannot see any trace of any of that now. The oil and shavings may have been inside from purchase. I had heard that if the oil is present to switch out the crankshaft seal and I will keep that in mind for sure if it reappears. I have a new magneto in the mail now. If the engine runs rough for a half mile and dies can the kill switch damage the magneto in that distance, or are you saying once it is running to reattach the kill and it should be fine. Thanks 2door.
 
2door

2door

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Staff member
Sep 15, 2008
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Littleton, Colorado
If the kill switch is the culprit it shouldn't damage anything. It might keep the engine from running if the contacts inside it are touching, even momentarily but not compromise the CDI or mag.
How do you have the ignition circuit wired? We always suggest that the white wire, if your engine has one, be isolated/unused and to use only the black and blue from magneto to CDI. The kill switch would simply jumper the blue and black wires.
Some newer engines come without the infamous white wire.

Tom
 
Moisstink

Moisstink

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Aug 2, 2013
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I clipped the white wire, soldering the blue to blue, black to black heat shrink tubes. I am hoping it was just another bad magneto. I will see this weekend. Thanks Tom,

Kevin
 
GearNut

GearNut

Active Member
Aug 19, 2009
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Check the black wire where it attaches to the magneto frame.
The wire should go to a ring terminal which is located under the head of one of the mounting bolts
They are known for having a poor solder job from the factory, a "cold joint".
Instead of heating up the wire and the ring terminal both until they are hot enough to melt the solder on contact, they just melt solder over the cold wire and ring terminal. Sort of a solder coating which will not be reliable what so ever.
Also, the mag frame and the ring terminal both need clean metal to metal contact with each other and the mag frame to engine case as well. The factory coats the mag frame and ring terminal with lacquer before assembly and this lacquer acts like an insulator.
Try removing the mag from the engine and scrape or sand the lacquer off only where a clean connection is desired; Ring terminal to mag frame and mag frame to engine, and mounting bolts to mag frame points of contact.
 
Norman

Norman

LORD VADER Moderator
Jan 16, 2008
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Lot of times the mag coil or the cdi is blamed for it running nasty or not at all.
There's other things that can cause a problem that isn't obvious.

What does your spark plug look like?
did you check it's gap before use? or just put it in the head?
What ratio oil to fuel you using?
do you know what size main jet and where is the clip on the needle?

cold solder joints and corrosion in the solder less connectors will also raise **** with your bike not running.
 
maniac57

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
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A new plug never hurts, especially if you are still using the chinese stocker.
They are prone to mystery partial failures and can cause problems.
NGK b7 or b8es or hs are the popular choices.
 
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