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Discussion Starter · #1 ·
Electrical issues not my expertise so I thought seek some help here. Lately my ST4 will stop running like I flipped the kill switch. Always restarts and might not do it again for 50 or 100 miles. But today I was going down the freeway and quit running again so I flipped the kill switch back and forth and it started running again before I even had to pull off into the emergency lane. Drove home and took apart the switch didn’t really see any corostion and wires looked fine. Are there any relays or anything that might be going bad ? Bike runs perfect and always restarts easily.
Thanks
 

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It could be the switch, but yes there are relays involved. Connections and plugs as well.

The kill switch is part of a safety interlock circuit that ultimately applies power to the injection relay (one that powers pump, coils and injectors). Part of that circuit includes the side stand safety switch and associated relay if you have that on your bike. So, in that list of components you have the potential for two relays, a side stand switch and several plugs that may have corrosion in them.

Do you have a side stand bypass harness installed? The add on harness that lets you start the bike with the side stand down in neutral. If you do, remove it for troubleshooting.

You feel the problem goes away by cycling the kill switch on and off. Good bet it is the switch, but understand it could just be causing the injection relay to cycle and then finally restore.

It may also be helpful to gather more indications. Understanding that this happens when ridding and all you want to do is get it running again, but noticing if the dash lights / head light also go out would be helpful. If that is the case, we are on to a completely different circuit and I'd suspect the main relay (yellow one) or maybe a loose or cracked filament (yes it can happen) in the main main fuse. Might also check the injection relay fuse while your at it.

You could start with the switch.
 
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Discussion Starter · #3 ·
Ok thanks, yes my bike has side stand bypass so I’ll start there. We’re can I find a wiring diagram to find these relays? To bad I just had the body work off for valves and belts a few months ago, it’s not that bad.
 

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