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Associated mag - no spark

highpockets003

Registered
My Associated 1.75hp was running at the show fine. Came time to oil it, so I squirted a drop here and there - at the mag gear and skew gear, I accidentally got the small oiler tip between the 2 gears for a split second - oops. They kinda munched on the oiler tip, and immediately the engine coasted to a stop. :mad:


Tested the mag at home and still no spark (engine does run on battery & coil). Disassembled the mag, measured the coil core at 6.0 ohms; seems reasonable. Each magnet will pickup one of the mag's side plates and hold it. I did have too much wet oil in the brass bushings, at each end of the mag; remedied.


Put the mag on the lathe and tested with 12vdc light bulb, 70-300 rpm; no illumination. I did notice when touching the light bulb lead to the coil's back end brass plunger while the mag is rotating, there is a small blue spark that jumps to the lead (using the mag body as ground). Measured the AC voltage output at the brass plunger; 7-9VAC. Check with light bulb again - and no illumination.


Don't know what I've done to the mag. :shrug: The coil measures a continuous 6 ohms any time I check it. The magnets seem okay. The coil rotor is NOT touching the side plates while rotating.


Ideas why the mag won't produce a spark? :help:



Thanks!
 

cobbadog

Registered
Sounds as if oil has got to a place where it should not be and is shorting to ground. A strip down and a good clean up and then check any and all wires just in case they are shorting for any reason.
Good luck with it and let us know how you get on.
 

DavidRaines

Subscriber
Last Subscription Date
10/26/2019
I would try and clean the pickup and brass parts. If oil gets on the pickup you won’t have spark. First engine I got had this problem.
 

Turbo

Subscriber
Last Subscription Date
07/12/2019
7-9 Volts AC is about what they put out. I have never tried to light up a light bulb with one so I don't know if that is possible. I think what happened is when the oiler tip went through the mag gears the shaft slipped in the armature changing the timing. Check the armature drive shaft for any play. If you don't find any re-time the mag and try again. Here is how I test for spark: Take the output wire and rest it on the mag gear while spinning. If you see sparks it will run.
 

highpockets003

Registered
Because I can't read and absorb destructions well from Harry's Old Engine webpage, I didn't time the mag correctly. :eek: The destructions clearly state the mag's L rivet indentation should be centered "...when the igniter snaps...". :bonk:

I was incorrectly timing the L indentation with the crank's and cam's timing marks. :headbang:

The engine started up on the first crank. :clap:
 

cobbadog

Registered
Glad you got it sorted and that it runs again. I know what you mean in understanding 'destructions'. I have been playing with our vintage David Brown and the terminology that the Poms used back in 1954 is totally different to what we call things here in Oz. Even had an issue re wiring the tractor after a restoration and wondered why it was not working at all. Then I remembered the bloody thing is + earth, swapped a few wires about and all was good.
 
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