D4 7U no spark on pony......magneto?

Hey Eganx,

Sometimes the on/off switch goes bad. Yes, it's only one wire going to ground. Remove the wire from switch and try to see if you get spark without the wire hooked up. If you do, you proved that switch went bad. Simply first step...

Hey Eganx,

Sometimes the on/off switch goes bad. Yes, it's only one wire going to ground. Remove the wire from switch and try to see if you get spark without the wire hooked up. If you do, you proved that switch went bad. Simply first step...

If your mag is an American Bosch MJK series, check the brushes. When the cap is off, there will be three brushes with springs. My pony motor had no spark, and when I pulled the cap, two brushes had broken off. Individual springs are available from Florin Tractor.

John

The points may look clean but the contacts need to be spotless and provide very low resistance when closed. A few passes with a fine grit sandpaper and then a few cleaning passes with white paper through the points should remove any contaminants and provide good conductivity.

Dirty points are the number one failure mode i have experienced with these magnetos. Easy fix.

[quote="Eganx"]I went to fire up the dozer yesterday and found the pony had no spark. I pulled the cap off the magneto and the point look OK. However I'm not familiar with magnetos. Is there anything specific I should look for?

It appears the ignition on off switch just goes to ground as it only has one wire going to it and then another wire going to the body of the switch which is in contact with the bracket that holds it. Is that correct?

Is there anyone out there who rebuilds these thing?

Thank you - Egan[/quote]

It's a "kill switch" wire. you want it open (not going to ground) for a spark, only going to ground for "off." counter-intuitive.

Cut the switch out of the loop.....no spark


So the magneto name plate says "standard magneto xh1907"

So would this be an aftermarket magneto? Everything looks quire fresh in there too. Its definitely been gone through in the last decade or two.

I didn't see any brushes to speak of.

[quote="Eganx"]Cut the switch out of the loop.....no spark


So the magneto name plate says "standard magneto xh1907"

So would this be an aftermarket magneto? Everything looks quire fresh in there too. Its definitely been gone through in the last decade or two.

I didn't see any brushes to speak of.[/quote]

Then you have a Wico magneto. That mag has the best parts availability as it was the latest type , along time ago.

Change the condenser/capacitor as it is the second easiest thing to do after cleaning the points.
Keep it simple, its not totally dead yet!