TOPIC:

I'm a new member and not very familiar with forums. I have a 1975 Z1 which I restored from a neglected state with a hideous seat, Vetter fairing, Kerker exhaust etc. It now looks original and goes beautifully except that occasionally it just dies, as if the kill switch was turned off. Lights etc stay on and I pull over, turn the ignition off and on again and it starts right up and runs fine again. I've checked coils, connections, HT leads, ignition and kill switches and all seem OK. It has a 19 year old Boyer electronic ignition and I'm wondering if it could be the ignition module going bad. Has anyone else experienced this problem? Thanks.

Coil supply is a common issue as these bikes get older, a common mod is to fit a by-pass relay in the coil supply. The below link explains the rational for the mod. Even if it's not your issue it's a worthwhile mod to get the best possible spark when starting

kzrider.com/forum/4-electrical/617512-ig...-pass-relay-w#866367

Also check the kill switch connections plate. Number of bikes I've seen were the plate is cracked and the internal connections on the plate are corroded is lots!.
If the connections are corroded as they get warm through current flow resistance will increase until the coils will not get any electrical flow. 
The kill switch is always causing issues on these old bikes. Easily bypassed to test it by joining the 2 wires that run to it together. 

It sounds like the problem is in the kill part of your right side control.  It may be at the switch itself or it may be one of the wires feeding the switch.  

That said, intermittent problems are the toughest to solve.  You may need to replace the right control to see if the problem disappears.  I may have a right side control in my spare parts.  I'll check today.

You should also check the wiring harness where it flexes around the head stock.
Internal breaks are common after many years of use.
With the bike running gently pull , jiggle and bend the harness where it emerges from the fuel tank towards the clocks etc and see it that cuts the ignition.

I had a bad ground wire that gave me fits .....just like this for months.
It would always start fine, but just the right vibration/turn and it would short out.

All good suggestions above. Intermittent electrical issues can be maddening, as one never knows if that last thing you tried really fixed it, of if it's just gone away (intermittently) once more, until an indefinite period of time has passed.

One thing not mentioned yet is the ignition switch. The solder joints on the backside of thew switch have been known to crack, leading to intermittent issues. The solder joint on the brown wire might be the culprit.

Please keep us posted with any updates, and welcome to KZR.

Good Ridin'
slmjim & Z1BEBE

Great suggestions, thanks everyone. I'll work through all those possible causes one by one and have ordered a new ignition module anyway. It's my first Z and a magnificent bike so well worth fixing as this cutting out problem is a disincentive from riding it on major roads -- could be tricky on the freeway. I've posted a couple of pics of it on the new members forum. 

zed1015 wrote:

You should also check the wiring harness where it flexes around the head stock.
Internal breaks are common after many years of use.
With the bike running gently pull , jiggle and bend the harness where it emerges from the fuel tank towards the clocks etc and see it that cuts the ignition.

I had this happen on my 76 900 and took a minute to find it, turned out to be the brown wire hanging on with just a few strands of wire

I also had an issue with the solder joints failing on the kill switch. I got it soldered back together just fine but still had an issue. Turned out that one of the wires occasionally touched the bar because it had slipped out from under the wire guide inside the control pod during assembly. I'd be riding along and suddenly the lights and blinkers started freaking out.

So after it dies the first time does it take the same amount of time to die again?
Or is it a longer or shorter amount of time before the next episode?

Does the starter button work immediately after it dies or do you have to turn the ignition off then on for the starter button to work?

It only dies once, usually fairly near the start of a ride, and not every ride, and after that it runs flawlessly. Good point about the ignition switch. I think I've always turned it off then on again (then it starts up immediately). Next time I'll try leaving the ignition on and then see if the starter works straight away. I'm about to fit a new ignition module and if that doesn't fix it I'll work through all the other suggestions one by one.