2000 M900ie starting issue, solenoid clunks, won't crank

[brad black]

i've got an m900ie in at the moment that has had ongoing starting issues over time (now at 120,000km).  press the start button and the soleniod engages, then drops out again.  not a fast click-click-click, but a clunk----clunk---clunk noise.

i figured it had a bad solenoid, but a new one disproved that.  i found that the earth side of the soleniod activation drops out when loaded.  it gets 12v from the button, and it has 12v on the other wire, cycling with the clunking.

the earth side of the soleniod activation goes to the ecu.  the sidestand input goes to the ecu as well (an earth), so i'm guessing stand down gives the ecu a signal that it's ok to let it crank.  with ignition off there's no resistance anywhere, but ignition on you get 150 ohms or so in the side stand circuit.  earthing the circuit at the stand connector doesn't help.  earthing the earth side of the soleniod activation wire just before the ecu makes it work fine with the button.

i'm thinking of cutting the earth side of the soleniod activation wire at the ecu and the side stand ecu input wire and joining them, so it has earth to the earth side of the soleniod activation wire with the stand up.  can't think of any issues with that at the moment.

the side stand circuit is just fed from the main ecu earths, and there's no issue there.  runs fine, so it's not an overall earth issue.

anyone have experience or know what i'm not seeing?

[Howie]

I'm not sure I follow what you are saying.  You are correct that the ECU allows the bike to crank.  Terminal 16 on the ECU is from the side stand switch.  Terminal 19  goes to the solenoid, orange/brown wire.  Running that wire directly to ground (I think) will allow the bike to crank.  The side stand safety feature would be bypassed though.  If this is a problem you could run a relay like on the carbie bikes. 

[brad black]

i'm going to cut and join the wires going to 16 and 19.

that way 16 will supply the earth for the starter solenoid when the stand is up, but not when down as the side stand circuit is just an earth and 16 is the end point.  through the side stand switch it joins the earth circuit going to 23 and 24 on the main earth loom.  it may even be the issue somewhere upstream of 16, in which case i'll just earth 19.  but i can't back probe the connector and it all changes once the ignition is turned on.  it just depends which side of what is the issue, and that i can't find.

and that bit really annoys me, as i want to know.

[Howie]

Doh!  Yep, 16 to 19 will work.  The fact that you get the clunk and ground disappears makes me think the failure is solid state or a winding.  Since the solenoid is good, there is no relay  and the bike starts with 16 and 19 jumped I think the fault would be in the computer.

[brad black]

i have another 1.5m here, no change.  which made me more perplexed.

it needs 16 into the ecu, otherwise nothing happens.  i popped the terminals 16 and 19 out of the connector (push the wide white tap in, had to move 17 and 18 out too to get 16 back in) and stripped a little insulation and soldered a jumper into each.  with the terminals out i could cover the splice with heat shrink, which makes me much happier.  then just joined and soldered the jumpers.

and that way, if the need arises to reverse it, you just snip and it's done.

cranks no worries now.