Neutral switch gremlins .. and .. The Sidestand Diode Mod.

utopia · 22-05-2019, 12:39 AM

For a while now, I've had a dicky neutral switch.
It glows nicely when the bike is in neutral but it also retains a dim glow when its in gear.
And its an intermittent problem .. sometimes it works normally.
This has been going on for a couple of years.

I probably would have thrown a new neutral switch at it ages ago but there was another element to the story which made me think that the problem might lie elsewhere.
A couple of years earlier I had added a diode between the neutral switch and the sidestand switch, so that the bike could be started on the sidestand as long as it was in neutral.
This was a mod which was suggested by ukmoc member "Xenocide", who also kindly supplied the diode.
At the time, various degrees of doubt were expressed on the forum about the mod, but the basic circuit logic seemed fine to my mind and the system appeared to work fine in practice.
However, I'm not very electrics minded and I was therefore a bit cautious that there may be unforeseen gremlins lurking.
So, when the neutral light went wayward, I began to wonder if the diode might be "leaking" somehow, or had maybe put undue electrical stress on other components of the system, eg the switch or maybe the relay.

Another reason for my delay in sorting it out was that removal of the neutral switch requires a special spanner .. I settled on a ring spanner with a slot in the head to enable it to pass over the switch wire and a double crank in the handle.
Then the other day, I realised that I didn't have to butcher a perfectly usable 13mm ring spanner because 7/16 AF is just a gnats tad smaller .. and after slotting it could be opened out to fit.
So I did that.

My plan was to try adjusting the shim thickness under the head of the switch, but once I had it in my hand it was obvious that the switch leaked to earth in any position and no amount of shimming would sort it.
The switches seem to cost £35 odd, plus postage or petrol to collect, so getting on for £50 all told .. and I'm all spent out on a forthcoming TT trip.
So I had a fiddle with the old one.
First I left it soaking in meths for an hour or so, agitating it and operating the plunger from time to time.
First try after that and it worked normally, but it soon reverted to intermittent failure.
I didn't fancy soaking it in anything which wouldn't fully evapourate for fear of contaminating the engine oil when I refitted it (ok that's super-fussy, but there it is), so ...
I then soaked it in clean engine oil.
I positioned it "open end upwards" in the oil, in the hope of expelling any air and allowing oil to fill all voids within the switch. I also pumped it from time to time and observed little air bubbles being expelled.
I should say that I was no longer expecting a result by now, I was simply giving it every last stupid little chance before giving in and buying a new one.

You can probably guess by now.
Yep, 250 miles today, around the twisties, through town and village, so lots of gearchanges and neutral selections .. its been perfect.
Who'd a thunk it ?

I dunno what the long term holds but it probably (or do I only mean "possibly" ?) will require a new switch in the not too distant.
For now though, I still have £50 in my pocket.

22-05-2019, 12:39 AM	#1
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	Neutral switch gremlins .. and .. The Sidestand Diode Mod. For a while now, I've had a dicky neutral switch. It glows nicely when the bike is in neutral but it also retains a dim glow when its in gear. And its an intermittent problem .. sometimes it works normally. This has been going on for a couple of years. I probably would have thrown a new neutral switch at it ages ago but there was another element to the story which made me think that the problem might lie elsewhere. A couple of years earlier I had added a diode between the neutral switch and the sidestand switch, so that the bike could be started on the sidestand as long as it was in neutral. This was a mod which was suggested by ukmoc member "Xenocide", who also kindly supplied the diode. At the time, various degrees of doubt were expressed on the forum about the mod, but the basic circuit logic seemed fine to my mind and the system appeared to work fine in practice. However, I'm not very electrics minded and I was therefore a bit cautious that there may be unforeseen gremlins lurking. So, when the neutral light went wayward, I began to wonder if the diode might be "leaking" somehow, or had maybe put undue electrical stress on other components of the system, eg the switch or maybe the relay. Another reason for my delay in sorting it out was that removal of the neutral switch requires a special spanner .. I settled on a ring spanner with a slot in the head to enable it to pass over the switch wire and a double crank in the handle. Then the other day, I realised that I didn't have to butcher a perfectly usable 13mm ring spanner because 7/16 AF is just a gnats tad smaller .. and after slotting it could be opened out to fit. So I did that. My plan was to try adjusting the shim thickness under the head of the switch, but once I had it in my hand it was obvious that the switch leaked to earth in any position and no amount of shimming would sort it. The switches seem to cost £35 odd, plus postage or petrol to collect, so getting on for £50 all told .. and I'm all spent out on a forthcoming TT trip. So I had a fiddle with the old one. First I left it soaking in meths for an hour or so, agitating it and operating the plunger from time to time. First try after that and it worked normally, but it soon reverted to intermittent failure. I didn't fancy soaking it in anything which wouldn't fully evapourate for fear of contaminating the engine oil when I refitted it (ok that's super-fussy, but there it is), so ... I then soaked it in clean engine oil. I positioned it "open end upwards" in the oil, in the hope of expelling any air and allowing oil to fill all voids within the switch. I also pumped it from time to time and observed little air bubbles being expelled. I should say that I was no longer expecting a result by now, I was simply giving it every last stupid little chance before giving in and buying a new one. You can probably guess by now. Yep, 250 miles today, around the twisties, through town and village, so lots of gearchanges and neutral selections .. its been perfect. Who'd a thunk it ? I dunno what the long term holds but it probably (or do I only mean "possibly" ?) will require a new switch in the not too distant. For now though, I still have £50 in my pocket.