Early A-10 magneto issues.

A friend is working on a 52-plunger frame A-10 and he is having K2F magneto issues. It starts and runs well but shutting it down isn't as easy as it should be.
It doesn't want to shut down, yeah odd. He tried to do a direct short to ground from the center stud to the primary, then with a wire from the center stud to the frame. I'm not well versed in magnetos, but he has spoken to Greg Porier up in Washington and he wants him to remove it and send it up to him. Could it be a wader magneto? I will ask him to send me pictures.

N0rt0nelectr@ said:

A friend is working on a 52-plunger frame A-10 and he is having K2F magneto issues. It starts and runs well but shutting it down isn't as easy as it should be.
It doesn't want to shut down, yeah odd. He tried to do a direct short to ground from the center stud to the primary, then with a wire from the center stud to the frame. I'm not well versed in magnetos, but he has spoken to Greg Porier up in Washington and he wants him to remove it and send it up to him. Could it be a wader magneto? I will ask him to send me pictures.

Click to expand...

Sounds like the carbon bush isn't making contact with the points centre bolt
Does the end cap screw on or is it held in place by a clip?

I think baz is onto the problem. Remove the endcap and check the status of the carbon brush inside. A new brush should take care of it. Cost about $1.

Slick

I think a defective earth brush can also cause this.

Under this slotted cap:

Usually the question is: why does my Maggie fail to start, not why does it fail to stopt.

Obviously, a defect in the earthing (ground) circuit.

Slick

baz said:

Sounds like the carbon bush isn't making contact with the points centre bolt
Does the end cap screw on or is it held in place by a clip?

Click to expand...

I contacted him last night and he sent me pictures of what he has. From the pictures it is the one with the plastic end cap.

N0rt0nelectr@ said:

I contacted him last night and he sent me pictures of what he has. From the pictures it is the one with the plastic end cap. View attachment 114721View attachment 114721View attachment 114723

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Ok tell him to undo the gland nut holding the white wire and check with an ohms meter that it makes an earth when the cut out button is pressed on the handlebars
If it does he'll need to remove the black plastic end cap
And check for continuity from the carbon brush on the inside
To the fitting where the white wire goes in

There should be a spring associated with that earth brush. Perhaps it is missing, which would cause erratic connection.

Slick

baz said:

Ok tell him to undo the gland nut holding the white wire and check with an ohms meter that it makes an earth when the cut out button is pressed on the handlebars
If it does he'll need to remove the black plastic end cap
And check for continuity from the carbon brush on the inside
To the fitting where the white wire goes in

Click to expand...

He says he removed the end cap and went from the end of the armature to ground and it didn't stop the mag.
I thought it might have been a wader mag but there is no evidence of this. I'm sure when he gets to the bottom of this it will be something simple.

N0rt0nelectr@ said:

He says he removed the end cap and went from the end of the armature to ground and it didn't stop the mag.
I thought it might have been a wader mag but there is no evidence of this. I'm sure when he gets to the bottom of this it will be something simple.

Click to expand...

This is daffy!
By "end of the armature" I presume the center fixing bolt, or screw, that holds firm the contact block assembly. If the mag did not stop, there must be an open circuit behind that fixing screw. That would be a job for a technician like Greg Poirier.

One trick your guy might try: attach the leads of a VOM, set to low Ohms, across the points. There is normally a closed circuit path across the points regardless if they are open or closed. If there is an open circuit when the points open, this is abnormal, and indicates some internal fault. Send the mag to Greg Poirier.

Connect VOM leads across A1 or A2 and B. With center fixing screw in place, there is normally a closed circuit regardless if points are open or closed. If open circuit when points open, then internal fault.






Slick

My friend checked out the plastic end cap and the spring was missing from under the carbon brush.
He asked me to thank you all for your insight. He said it was nice to have a kill switch that works.
Cheers

N0rt0nelectr@ said:

My friend checked out the plastic end cap and the spring was missing from under the carbon brush.
He asked me to thank you all for your insight. He said it was nice to have a kill switch that works.
Cheers

Click to expand...

Actually, the spring was missing in the ground brush holder. The carbon brush was riding on the armature by gravity. On some of the older K2F's, there is a grounding brush on the back of the points plate which may have been the reason why it sparked. Never the less, once the grounding brush was making good contact, the kill switch could do the job.