MS2 only runs on START...?

[cahillicus]

Recently my MS system left me broke down on the side of the road and I have since been trying to figure out the problem. Since then, I can't get it to start. It will stumble and fire but as soon as you let off the starter, it instantly dies. Last night, I pulled off the throttle bodies and put on carbs in an attempt to narrow the problem to fuel or fire. The bike started right up and runs as long as the starter button is held down, but immediately cuts out as soon as I let go of the starter button. So, either the ignition system or the whole MS is cutting out once I let off the starter. can anyone think of what could be going on. Keep in mind that this setup used to run well.

[DonTZ125]

I'm looking at the wiring diagram for an XS100SH - what a mess ... There's relays in there that I can't figure out what they do! 2 kill switches??


The most likely thing is that a safety interlock has come unglued - neutral switch, clutch switch, emergency stop switch - preventing the TCI from playing nice. Another possibility is that you've fouled a plug. Worst case is broken hard parts.

[cahillicus]

The TCI is gone and MS runs the show. No hard part problems at all, as it runs perfect (on carbs) with the starter button held down. As soon as you let go, dead.

[DonTZ125]

If it dies as soon as you release the start button, it isn't running perfectly on carbs ...

[cahillicus]

Wrong. It dies because the ignition cuts out when the button is released. The carbs work perfectly.

[DonTZ125]

Whether the failure is in the carbs, injectors, ECU, or dilithium crystals, it stops working once the start button is released. Ergo, it does not run perfectly.

[cahillicus]

If this is you helping, stop. It's not helpful. I am looking for answers, not smart behind responses. Thank you. Have a nice day.

[Matt Cramer]

It sounds like something - either the MS or the coils - is losing power; I'd investigate all points where everything MS related is supplied with voltage.

[DonTZ125]

Get over yourself. Not everything is deadly serious.

I've seen grip switches - on both sides - shake apart and do stupid power tricks. You might want to strip and inspect your right switch pod (start and kill switches), looking for loose or broken wires. This is the first place that 'ignition power' and 'starter power' cross paths, and so the most likely culprit. Unplug the right switch pod as well, and inspect the connector.

Power feed checks:
1) Run a flying wire from the battery to the MS, so it's powered independently of everything else. Does it start and continue to run? If yes, the MS power system is at fault.
2) Run a flying lead to the coils from the battery. Does it start and continue to run? If yes, the coil power system is at fault.

If BOTH checks show vast improvement, the fault is upstream of where the MS and coils power feeds split off.

[cahillicus]

Thanks, those are both great ideas.