Coil swap on a Martin 75

[asdasc]

I have an old Martin 75 with crumbling coils. The coils from a similar year Johnson fit over the Martin laminations, but the top wire doesn't quite reach the condenser. The black ground wire reaches. Does the polarity on the coils matter?

 

[steelespike]

Re: Coil swap on a Martin 75

Just a guess but it seems to me it does mater. If you reverse the wires on the old auto ignition system iot bwill work but
will eventiusally damage the ignition components.
Just extend the positive wire, solder on an extension and put heat shrink tubing on it.
I also have a Martin 75 that I may have to replace a coil.

 

[F_R]

Re: Coil swap on a Martin 75

It matters. The one wire grounds both the primary and secondary windings of the coil.

 

[asdasc]

Re: Coil swap on a Martin 75

Ok thanks guys. From, it was very easy to remove the old Wico and fit the new Johnson coils to the old laminations. I will post pictures.

 

[asdasc]

Re: Coil swap on a Martin 75

Ok, I was able to make the wires reach, but still no spark. Kludged in a Johnson condenser, and still no luck. That's when I realized that I had taken the Johnson parts off a motor I was having trouble with, so tomorrow I will test them individually.

 

[F_R]

Re: Coil swap on a Martin 75

Wico points develop a soft corrosion on the contact faces. Looks almost like mold. That stuff is non-conductive, and must be removed. Take the points completely apart and individually clean each contact shiny bright with some 400 grit sandpaper, and reassemble and set gaps to .020". The points are very difficult to get clean without taking them apart.

 

[asdasc]

Re: Coil swap on a Martin 75

Thanks FR, I will try that. I used a small thin file and just made a few passes without taking them apart.

 

[ronboonville]

Re: Coil swap on a Martin 75

On my martin 60 I had intemitant spark. caused by a build up of gunk on the bakelite parts that slide. they just wren't going closed fast enough. Cleaning these parts and where they fit made a lot of difference. I took my coils from a 1957 firestone. correction, I used the coils from the firestone on my martin 45..

 

[asdasc]

Re: Coil swap on a Martin 75

FR, you were right! I took it apart again tonight and disassembled the points, filed off the oxidation, and now have great spark on both cylinders! Thanks for the help.

Ron Boonville, that's interesting and worth checking out. I didn't really clean up the bakelite parts. Are they supposed to be lubricated with anything?

 

[F_R]

Re: Coil swap on a Martin 75

Are they the sliding type of points? The slider should be lubricated VERY sparingly with lubriplate. Just enough to say they aren't dry. Too much will foul the contacts. The pivoting type don't need any lube, but again VERY little lubriplate on the pivot won't hurt. If I remember, both kinds have a cam wick, right? It's been a long time. I guess my last Martin was about 10 years ago.

 

[ronboonville]

Re: Coil swap on a Martin 75

What Frank said. I don't remember a wick either. Mine are the sliding type and I just put a film of lube on them.

 

[asdasc]

Re: Coil swap on a Martin 75

Yes, these are the sliding type and have the cam wick. I will attach some pictures. I don't think that I can from my cell, so will need to wait until I am back at the computer.