503 Starter

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503 Starter

Postby robbgass1 » Mon Dec 19, 2016 5:01 am

I've been trying to fix up and get running a 503, which has electric start. It has not run for 40 years...cleaned out and repaired mechanicals, then rebuilt carburator, new battery, and turned over engine and got her to fire and almost keep running....when putting her back together I somehow goofed up the ignition switch(It was touching the metal, and I think it should not) and when I turned key to start nothing happened and electrical type smoke began gently floating up from engine area...I'm guessing I burned up the starter motor, dangit. Does this sound right?
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Re: 503 Starter

Postby Schoobytwo (Bruce) » Mon Dec 19, 2016 8:53 pm


I would start by asking about the key switch. The original key switches have the five posts on the back of the switch but around the outer edge. These switches have been known to come apart internally and then short out. If lucky, only the switch burns. If unlucky, it can burn the wires clear back in to the motor. If you have one of these old switches, replace it with a new switch that has the terminals in the middle of the back.

These starters are brush and spring type starters. If any of the brushes are not contacting the commentator good, they will arc and smoke as you describe. If a spring breaks, it is the same issue. If you happened to clean the starter (even just the outside) with any sort of flammable solvent like Brakeleen or other solvent, you may have very well got some of this solvent into the starter solenoid and my experience is they burn up quite easily if they get any sort of solvent in them.

If the starter no longer works, I suggest to remove it and check the brushes then bench test it.

The original wiring will have the wiring positive hooked to the positive post on the starter. I like to move this to the positive post of the battery and add a in-line fuse.

Those should be good for starters (get it :D ). Let us know what you find.

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Re: 503 Starter

Postby robbgass1 » Thu Dec 22, 2016 5:10 am

For starters, Bruce, thanks for the advice.

I think what happened is I put a plastic spacer in the wrong place so that the ignition switch was mounted directly against the metal body...to make things worse, after I turned the key to 'start' and nothing happened but smoke, it was stuck and I couldn't turn it off. It is the old school switch.

Will you do this for me...sell me all the parts that you figure I cooked and I will start fresh with it.

It looks as if I must remove the engine to access starter, true?

I may have more question later, electricals is not my strong suit...in fact, I don't think I have a strong suit...saddest part is that she was so close to being ready to ride.

your friend and mine,
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