Solenoid wiring

[bloglos]

I'm about to start wiring up a bike I've been building for a while now. I've photoshopped up a diagram for my '80 XS650 which I've attached below which should work fine, but the problem is I bought the bike from some kid and the starter solenoid has 3 posts instead of 4. I'm a little green here but from what I understand completing a circuit from the 2 smaller posts opened the relay and power goes to the started from the thicker cables as it takes some serious amps to fire up the starter.

So how do these 3 post solenoids work? Is it grounded at the body? I'd love a little help!

 

[retiredgentleman]

I suspect the small terminal needs to have +12 volts applied, with the relay's coil being completed to ground by its metal mounting lugs.

You would have to use either a push button, or an ignition key that has a "start" position such as used on cars/trucks.

So unlike the stock Yamaha circuit that uses a push button to switch ground to the relay coil, you need to switch +12 volts to the relay terminal.

 

[member3480]

That is a car solenoid . You would be better off getting the right one so your push button would work correctly. That there is voltage in one side voltage out to starter and single wire to starter switch. Ground is bolt to frame. Its a over kill for a bike but will work.