7245 Starter Motor Question

[andy_jordan]

I had some problems this past weekend with a lot of sparks from my starter motor. Turns out that the connectors for the battery and starter cable were rusted through and were shorting out. Unfortunately the nuts and bolt were also rusted through and I managed to shear it trying to remove.

The bolt looks 'kinda weird' - it looks like a regular 1 inch long hex head bolt but it has a circular copper contact in the top of the head. It looks like that connects with another copper contact on the starter motor, but I've never seen a bolt like this and have no idea where to get one. So my questions are:

Anyone know what the bolt is called?
Anyone know where I can get one (in Canada)?
Can I replace with a regular steel bolt - presumably the copper is only to make a better contact?

It's very frustrating to have an inoperable tractor because of a 50c bolt!

Thanks,

Andy

 

[zetor3545]

I know what you mean but have no idea wot its called. do you have a zetor dealer you can go to??? or try and make something up

 

[andy_jordan]

I may end up having to source via a dealer or have something made - just trying to avoid a delay if it's simple.

I guess worst case scenario is I just buy a steel bolt and try it!

 

[zetor3545]

there is nothing wrong using a steel bolt it works i have replaced copper ones with steel ones on many tractors. just put patroleum jelly on it to stop it rusting problem sloved good luck

matt

 

[andy_jordan]

So I found out why the copper is there from a friend of mine who restores old cars. I'm no electrical engineer so may not be explaining this right, and I still don't get why this application needs it....

Apparently when you have two dissimilar metals forming a contact it effectively creates a diode with electricity flowing better in one direction than in the other. By having copper to copper at the key part of the circuit - the terminal on the starter motor you get around that problem, although of course it still happens on the head of the steel bolt. Apparently one of the side effects of this type of connection is that it dramatically increases the rate of corrosion, which was the start of my problems in the first place.

Bottom line, replace the bolt with stainless steel and use a copper washer or fashion something out of copper flashing as the contact - the way that the bolt is held in place should hold the contact firm with maybe just a washer as a shim.