So, after sorting out my intermittent engine cut-out that eventually made the bike too risky to use, I now have an intermittent starting issue when the bike doesn't turn over. When the engine does start it works as perfect as you would expect (Hope), engine spins over fast and catches pretty much immediately but when it doesn't, it's just dead, zilch so I'm sure it's electrical. I've done some investigation and found the following. Bear with me as I'm trying to provide as much helpful info as possible

First the spec to help eliminate suggestions or ideas regarding upgrades as I'm sure there is a fault rather than just low spec electrics:

John Walker cables

150A Starter Solenoid (From Griff, about six years old)

High CCA fully charged battery in good shape (The bike has started instantly today, then it failed to even try to turn over and then it started instantly again without doing anything to the bike.

What I've done:

- Previously sorted the ignition switch problem, ref here: http://rsvr.net/topic10623.html" rel="nofollow - http://rsvr.net/topic10623.html

- Opened up the starter button switch on the bar, cleaned up all the contacts etc and re-assembled

- Disconnected all the connector plugs from starter button through to starter solenoid. They were very good (It's always pretty much been a dry weather bike) but cleaned all contacts anyway. Tried to find any intermittent connection by wiggling wires, connectors etc, nothing found

- Checked connections at solenoid, all good

Having checked all the connections were good and reliable I started checking for voltage and and continuity through the circuit:

Findings:

- There is reliable continuity all the way from live into the starter button switch all the way to the switching side of the starter solenoid

- The switched side of the solenoid has solid reliable connections providing power into and out of the solenoid to the starter motor

- A good 12.8V into the switching side of the solenoid

Two issues I did find:

- The return wire on the switching side of the solenoid goes into a Diode (Connected to clutch and side stand switches) so you cannot really test it goes to earth (At least I don't know how to test that!). Could it be a faulty Diode giving intermittent starting (My thoughts are not)

- There is a back feed of 0.25V from the ECU (as these connections are piggy backed) into to the feed wire to the switching side of the solenoid (And also therefore, back to the starter button) when the ignition is switched on (Nothing with ignition off). Is this correct/normal or does it indicate a problem?

After all this, I think I may have a faulty starter solenoid giving intermittent operation but the above questions are playing on my mind.

Any thoughts appreciated?

I can’t offer anything but this interests me. I have this problem when hot. 

Sometimes maybe one in twenty it doesn’t do anything on the button. Leave it or turn it off and on again and it’s always fine. Never done it once from cold.  Did all you suggested and replaced solenoid as I’d done all the tests. Still does it occasionally. Really odd. I have bypassed both clutch switch and side stand however. 

If you have power 'out' of the starter solenoid to the motor make sure you have it when the bike dose not turn over. Check at the starter motor nut with multimeter. 

"Make sure you check at starter motor nut when it dosent start" it you get V

And it dosent turn its proably a tired starter motor.

The motor earths through the enging then onto either the frame or direct to battery.  Worth cleaning up earth aswel just in case.  

 

Do a live test "starting conditions"

Hope this helps mate

When it’s in the fault state does the fuel pump still prime ?

Thanks guys,

Pete, yes power right through the solenoid but not had a meter on it when it faults. Given the mileage (approx 9K), how clean it is and how well it spins when it does spin, I don't think it will be a tired starter. Or an earth either but won't take any harm to check them.

Spoonz, thanks for the confirmation, I didn't think the ECU voltage would be an issue but my electronics knowledge is limited. Re the fuel pump, yes I think it does still prime but I'm not 100% sure.

A little more live testing maybe needed. I think I will disconnect the 'Hot' side of the starter solenoid first as that way I'm not constantly trying to run the starter and flooding the engine as it probably spins four times out of five.

That’s what I did to do my tests. Mine is virtually identical other than it’s very rare it happens 

Good plan ,I should have thought of that.    However ideally, I don't want to keep spinning the starter either for the sake of the sprag

I thought my issue was connected to the ignition switch problem I had but clearly it's a different cause.

snowman wrote: Just make sure you have voltage at press button side of solenoid when fault occurs , that would be my first check , “sorry if you’ve already checked this “

I've kinda checked this by checking on the upstream half of the solenoid connector and it never fails to show a voltage when I press the starter button. As the two leads from the other side of the connector disappear into the solenoid under rubber sheathing it's not actually possible to get to the terminal to check with the connector block connected if you get what I mean.

More testing later

So, an update as the problem has been identified and fixed. Although quite an obvious one, it is a little unusual so thought people might be interested.

The starting problem seemed to go away but would occasionally still randomly appear. Then this week it would only turn over maybe once in ten attempts so it needed to be looked at again.

Because I could always hear the solenoid clicking, I had (Foolishly) never put a meter on the switched output side of the solenoid (That goes to the starter) and assumed that if it was clicking then it was making the circuit. So this time a meter on that post whilst pressing the starter and - you guessed it - when it cranked there was voltage and when it didn't there wasn't! Every time though, the expected 'click' was there.

So, new solenoid ordered from AP, fitted today, and problem solved.

I had made the assumption that a click meant the solenoid was working when obviously there are many potential failure modes that a solenoid can suffer from but this one I have never come across before. Continuous cranking due to contacts welding together, yes. Switch not working (Therefore no 'click'), yes. But a click (So switch operating) but with intermittent making of the circuit, never before. Worth people noting I would say. I think I will cut the old solenoid open and see what happened, might be educational!

By the way, I ordered the new solenoid (And some other service bits) from AP at lunchtime yesterday and they arrived 10.30am this morning, exceptional service as usual  

Also by the way, AP have a bit of a sale on at the moment with decent discounts on service (Oil, filters etc) and cleaning stuff so take a look.