Mounting Emgo Coil on 750 twin

Just got a new Emgo ignition coil for my 1979 KZ750 twin from Z1. It doesn't fit.

Everywhere I look online I see this coil listed as fitting my bike and the description clearly states the mounting bolts are 3.5" (90mm) apart, which they are.

Here's the thing, the mounting points on my bike are 4" (101.5mm) apart.

Surely I'm not the first 750 twin owner to run into this. Any suggestions?

If you haven,t already, can you just drill 1 new hole in the mounting bracket. Some of the coil brackets have two holes.

The Emgo coil I have has the 3 1/2" spacing for the bolt holes. I think it was sold as to fit the points fitted 4 cyl bikes.

Motor Head wrote: If you haven,t already, can you just drill 1 new hole in the mounting bracket. Some of the coil brackets have two holes.

The Emgo coil I have has the 3 1/2" spacing for the bolt holes. I think it was sold as to fit the points fitted 4 cyl bikes.

I don't want to drill holes in the bracket unless I absolutely have to. I'm not even sure that will work as 3.5" puts one of the posts right on the edge of the bracket.

I'll call Z1 today and see if they have a different coil and/or suggestions for mounting.

Out of curiosity, have you measured the primary and secondary resistance to see how it compares, Caps in place?

Yep. On the secondary winding with no caps I get about 13 ohms. With caps I get about 24 ohms. And I get 4 ohms on the primary. Just like my old coil.

I'm going to keep the new coil anyway. I figure the old one is OK now but a 32 year old coil is a ticking time bomb.

Plus when I pulled the old coil completely off the bike I could see a place where one of the leads is about to break.

Called Z1 and talked to a guy in tech support.

He couldn't find an aftermarket coil with the properly spaced mounting points. But he said not to worry about it.

He suggested mounting it with one of the mounting screws and then just rig the other end so it is secure, maybe with some zip ties. The coil doesn't ground through the body so as long as it is secure I'm OK.

Fortunately it's way up under the tank where no one will see it. I might make a little dog leg bracket out of some aluminum stock or I might just zip tie it.

Topper wrote: Just got a new Emgo ignition coil for my 1979 KZ750 twin from Z1. It doesn't fit.

Everywhere I look online I see this coil listed as fitting my bike and the description clearly states the mounting bolts are 3.5" (90mm) apart, which they are.

Here's the thing, the mounting points on my bike are 4" (101.5mm) apart.

Surely I'm not the first 750 twin owner to run into this. Any suggestions?

I made a short extender piece with two holes in it out of some scrap material.

I agree, make a little extender bracket out of a strip of steel. Make sure it's steel because it has to transmit magnetic flux to the frame in order to complete the magnetic path through the coil.

Not completing the path will reduce the inductance/impedance of the coil (but not the resistance).

The guy at Z1 seemed pretty sure the coil didn't need to connect to the frame.

But one of the mounting posts on the coil looks like it is supposed to make contact with the leads going to the wiring harness. I went ahead used that mounting point as it was intended.

Then for the other mounting point I used a little strip of aluminum.

It feels pretty sturdy but looks like some idiot who doesn't know what they're doing hooked it up.

Oh wait, that would be me.

i just drilled another hole, bolted it in and worked fine.

It only needs the full magnetic path in order to take full advantage of the coil's potential energy. The bike doesn't need that much spark energy so it should be fine with a slightly reduced amount.

None of the harness wires for the coil are intended to be grounded. There should be no contact between any primary wires and frame ground.