Farmall BN no spark

spf150

Member
I've got what I believe to be a 1947 Farmall BN that has been sitting for 7 years or so and I can't get it to spark. The points are opening and shutting and I put in a new condenser. I suspect it's the coil inside the magneto?

Anybody know where to look next?

I hooked up an inline spark tester and we were getting a very very weak spark on the first crank but that's it.

Also, the wire that comes off the side for the kill switch gets grounded to the chassis(+GND) to get it to run, correct?

Many thanks!
 
The terminal on the mag should not be grounded to run. It is the Kill switch wire connection and can be left disconnected. The little gears on the rotor shaft must be timed to assure spark to the cap tower terminal. Jim
 
there is an L and an R on the rotor gear. the R should be lined up with the timing mark on the drive gear. Send me a private message if you want and I will reply with a phone number. I'll be happy to talk you through this.
 
Clean the points as they probably have a coating from sitting and you should have spark again. Kill sw is for stopping engine. Just had a mag off an H that hasnt ran in yrs. Cleaned points and mag fired like new again.
 

Thanks guys. I will give it a try then get back to you you guys.

Best way to clean off the points?
 
if you ground the wire attacked to the side of the
magneto it will not run. I would replace the
points with a new set.
 

What's the gap for the points on this set up?

I did notice the floppy armature or the point is blued from heat and the new one is shiny metal.
 
Everybody has given you good advice.You said you put a new condenser in it. I have had new condensers that were bad right out of the box. This doen't happen very often but it does happen.
 
(quoted from post at 04:47:00 09/22/14) I think points gap for a mag is .013.

Can you hear the impulse snapping when you crank it over?

When I turn it one way there is a resistance with the spring and a definite WHACK if you keep turning. If you turn it the other way it is much easier and you can feel some resistance with the magnets.

Gonna try replacing the points today and test it on the bench. If that doesn't do the trick the only other thing left to do is the coil, correct?
 

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