TOPIC:

Folks who have a strong handle on wiring, wondering your thoughts on a situation ---

I'm dealing with a no-spark situation on my twin. Turns out that my coil was bad. So I replaced it with the emgo 4ohm on z1.

Problem is - with the new coil in, when I connected the the new coil wire to the ignition switch wire, turned the ignition key to on, and then put the engine switch to run - the main fuse blew. Keeps happening, and I'm not sure why. What could cause the fuse to blow ONLY when the ignition coil wires are connected and engine switch to run? The points wires are not the issue. And, when the engine switch isn't on "run", the fuse doesn't blow and it's fine.

. Any thoughts? FYI - image of wires in question attached.

Does the fuse blow if you leave the coil disconnected and turn on the ignition switch?

Go buy a bunch of fuses that are rated correctly. You may be blowing a few in tracking down your issue.
Fuses are cheap.
Get Littelfuse or Bussman.
Whatever you do....DO NOT get a fuse that is rated for higher amperage than stock.

A fuse with higher voltage rating is ok.
A fuse with higher amperage rating is NOT ok.


 

Hey. The fuse does NOT blow when I leave the coil disconnected from ignition switches. 

Once I connect them, it blows right when I switch to "run". It also doesn't blow when I connect coil to points. So it's not that wire. 

And yeah... Unfortunately the person before me put in a 30amp fuse when it should be 20. But yeah. Does not blow when coil is disconnected. 

wrote:

Does the fuse blow if you leave the coil disconnected and turn on the ignition switch?

Get Littelfuse or Bussman.
Whatever you do....DO NOT get a fuse that is rated for higher amperage than stock.

A fuse with higher voltage rating is ok.
A fuse with higher amperage rating is NOT ok.



 

Believe it or not on other FB motorcycle forums, guys have suggested installing higher amp fuses and watch to see what wire starts to smoke. Not Kidding!

Here’s Two things to check real quickly. Make sure the yellow/red isn’t touching the frame. Second, check the clamp at the new coil that it didn’t get crimped down to much and shorting out the Yellow.

Beyond that you in good hand with F64.


 

Will check those thank you! 

Something shorted or connected incorrectly.
Do you have a wiring diagram ?
Click on the Filebase Tab up above. From the dropdown click Search Filebase. In the search box type kz750B1. There you will find a colour diagram which will show what should be connected to what.

At least the ignition circuit is pretty simple. You can see power/brown wire from ignition switch go to harness. Brown wire from harness go to kill switch. Red/Yellow from kill switch to coil .  
Like F64 said you will need a bunch of fuses. He is the expert

Here is a general recommendation.  If you blow a fuse you have major fault in your wiring, and you should not install a new fuse until you have figured out what the issue is.

The wiring on these old KZs was marginal from the start.  I know the 1000 and 650 have a 20A main fuse, and I can say from experience that the fuse box generally melts before this fuse will blow.  All of the wire, connector, and switches downstream from this fuse are not fully rated for 20A fuse.  Each time one of those fuses pops, a lot of things in the harness got really hot along the way, maybe hot enough the melt.  Doing this multiple times, in the process of diagnosing a fault, is likely to cause damage to other components on the bike.

Unless you do something really obvious like touch two wires together and see a big spark, you need to try to find the fault without blowing more fuses.

Of course I freely admit that I have not always followed this advice.  I melted two fuse boxes before I found the intermittent fault on my Z1R.  That's how I can confidently state that it's a bad idea.
 

Got it! Yes. The wiring is actually kz750b4 Wiring. So I have looked at that. I'm not toooo familiar with electrics so I'm just having a hard time where to start. But yes the diagram has been helpful. 

You might want to take a look at the fault finding guide I posted today. It will take you through step by step how to trace the "short circuit" that is blowing the fuse. Be lucky

I had a bit of spare time today so I have put the attached test plan together for you. This will identify what your problem is without the need to blow a bucket full of fuses. Be lucky

This is awesome. Thanks a bunch I will get to it next time I have a chance!