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Discussion Starter · #1 · (Edited)
Just when you thought Forchetto couldn't think of something even less interesting than his last thread all about inflating your tyres properly, here's one all about that fascinating (?) item: THE NEUTRAL LIGHT SWITCH.

It gets mentioned quite a lot in these and other forums so I thought it was worth doing a definitive article about it. Here's a typical thread:

http://www.triumphrat.net/twins-technical-talk/128082-neutral-switch-failed.html

I have added "Boring" to the title so don't come crying to me if you click on it and don't like it.

What's it for?

I don't remember seeing an idiot light to indicate you were in neutral before Japanese bikes came on the scene in the early 60's. Nowadays we seem unable to do without it. It's not that difficult to find neutral without the aid of a little light, really. Some bikes are better than others though, and the Bonnie is up there with the best. Neutral is really easy to find, at least on mine.

In the past some bikes had a mechanical gear indicator, a tiny pointer on the gearbox itself moving on a quadrant that showed N,1,2,3,4.

A particularly clever device was Royal Enfield's unique "Neutral Finder". This took the form of a little foot-operated lever on the gearbox that would force the gearbox to return to neutral if you stopped in any of the top three gears. One jab on that lever and the box returned to neutral. Magic...

An automatic device is used to this day on Kawasakis called the "Positive Neutral Finder", this is a fiendishly clever and exclusive device which allows for easy and accurate shifting from first into neutral while stopped.This avoids that annoying trait of many gearboxes where you try and click into neutral from first and it shifts into second gear instead, bypassing the neutral position. As soon as the bike starts moving the mechanism disengages itself allowing second gear to be selected as normal. Brilliant device that.

However manufacturers and Safety people have got together and decided that they would complicate matters a little and have linked the starting circuitry not just to the sidestand safety cut-out switch, but to the the clutch as well on later bikes and, for good measure, the bike won't even start with the sidestand down if that little green light is not shining.

This is to stop the bike lurching forward or even running away if the starter is activated with a gear engaged, unless you also have the clutch pulled-in.

What is it, where is it, how does it work, and what does it look like?

First here's a photo showing its location:



I tried to find where this switch was located right from the beginning. I searched for it as soon as I started to familiarise myself with my new Bonnie and looked in all the usual places where all my other bikes had it. The usual place was somewhere near the end of the gear selector mechanism, mostly hidden behing the gearbox sprocket cover.

Not on the Bonnie though. Unusually ours is located under the engine next to the oil filter cartridge. It's not worked by the gear selector mechanism but operates directly off the gear shift drum. It's also unusual, as far as I now, to have the gearshift drum under the gearbox, it's normally on the top of the gearshafts on most bikes. Perhaps it's something to do with the way Triumph have used a Triple gearbox turned upside down on these bikes.

It consists of a steel body that contains within it an insulating plastic insert, a Fast-On terminal for electrical connection, and a brass plunger. This plunger is connected to the terminal by a fairly strong spring that allows the plunger to move in and out of the body and also provides electrical continuity between the plunger and the terminal. The innards are then sealed with epoxy resin. It is supplied with a thin aluminium crush washer and the body is threaded M10 to allow it to be screwed to the crankcase via its 14mm hexagon head.

It appears that this crush washer is a bit special. Thinner than the usual copper or aluminium sealing washer at just 1.00 mm thick (Normal ones are around 1.4mm thick). The reason for this is that this washer sets the depth of reach of this switch and it could be critical as we shall see later.




Until I obtained a spare one to have a look at I wasn't aware of the fact that it's not a switch at all. It's really half a switch, just an electrical contact. The other electrical contact needed to complete what we think of as a switch, is the surface of the gear shift drum itself.

The photo below shows a gearshift drum and points to the groove where I think the switch operates. The groove is deep enough to ensure that the switch plunger clears the surface and doesn't make mechanical and electrical contact over most of its rotation. There's a raised section than when in neutral coincides with the plunger. This completes the electrical circuit to ground through the gearbox internals.

I might be wrong on this as I haven't yet seen the inside of my Bonnies engine and only found that photo on the net. If you know different please let me know so I can edit this.



The neutral lamp has one end connected to +12 volts and the other end has to be connected to ground or -12 volts for it to illuminate. In the neutral position the plunger completes the circuit to ground through the steel gearshift drum.

What can go wrong?

By far the most common complaint is an oil leak from that switch. This can have various reasons:

1.- Switch is not tight enough. Note that the torque recommended is just 10 Nm (7.3 Ft/lbs) even though the switch thread is an M10. This is just over the normal tightening torque for an M6 fastener (engine outer case screws, for example, are 9Nm). It could easily loosen itself a bit and create a leak. The switch lives immersed in oil so any
weakness there will cause a leak. Try pulling off the wire and re-tightening it first using a suitable wrench as shown on the photo (14mm deep socket or box wrench).

2.- The crush washer has lost its sealing properties. A new one is supplied with the switch, part number T1190014, but it's also available separately. Ask for part number T3550546.

You could try using an ordinary copper or aluminium washer but watch out for the thickness. If too thick it might hold the plunger off the gearshift drum and not make contact. You could sand it down to size I suppose.

3.- The epoxy sealing around the terminal has failed. This appears to be by far the most common cause of a leak and the only solution is replacement of the switch.

Another problem that is quite common on other Triumphs but I have never come across it on Bonnevilles, at least on this forum, is that the either the plunger or the gearshift drum contact surface wears and the failure to make contact not only prevents the neutral light from operating but also inhibits starting unless the sidestand is retracted. This is due to the neutral switch being electrically linked to the other two safety switches: the sidestand and the clutch switch.

A cure suggested in other forums is to grind the washer down by 10 or 20 thou and refit. The plunger will penetrate a bit deeper into the sump and resume making contact.




D'ecosse has ilustrated the reason on the schematic shown below of how the switches are connected on the carbed Bonnies at least. On the EFI models all safety switches operate through the ECU but the result is the same, if the neutral switch fails you can't start the engine unless the sidestand is retracted.

Link to schematic:

http://www.triumphrat.net/memberalbums/data/1217/Bonnie_start_light.jpg

Testing of the neutral idiot lamp and disabling the switch to enable normal starting is very easy:

Disconnect the wire to the switch, turn ignition ON and touch the wire to a ground point. The lamp should light. If it doesn't the chances are that the bulb is blown or there's a break in the wire. If the light won't go off even though you're not in neutral, it means that there's a short to ground somewhere along that wire.

If you need to disable the non-starting issue connect this wire temporarily to a good ground. The light will stay on but the engine can be started as normal with the sidestand deployed.

To disable both the switch and the light connect pin 10 on carbed bikes igniter unit to ground. See post 12 from Northern Thrux a bit further on.

For the EFI models, at least on the mechanical speedo ones, you could disconnect the Black/White wire that goes to the ECU's pin A31 and connect that terminal to ground.
 

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Forchetto,
Some day I will compile a complete addendum book from your posts & add it to my service manual for quick reference.
Even better, you should write a maintenance reference guide for our Bonnevilles and sell them for a modest fee. Your pictures and explanations are better than any service manual that currently exists.
It may seem "Boring" but at some point all of us are for the better because of your efforts.
Thanks again
 

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I test rode a Bonneville at a local dealership. The bike I test rode already had 150 miles on it. It had been used as a demo and test-ride bike (lots of different people taking short rides). Neutral was really difficult to find. Almost like there was a problem with the bike. The dealer said it was so hard because it still needed to be broken in. The SE that I bought had .5 miles on it. It's really very easy to find neutral. Probably easier than any bike I've ever ridden. I feel like the demo bike had been damaged or improperly broken in for the first 150 miles, and this made neutral almost impossible to find. Could this be the case? Any thoughts, Forchetto?
 

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Discussion Starter · #8 ·
I feel like the demo bike had been damaged or improperly broken in for the first 150 miles, and this made neutral almost impossible to find. Could this be the case? Any thoughts, Forchetto?
Probably had too much slack in the clutch cable. This makes neutral hard to find.

I find that 7 or 8 out of 10 bikes where I feel the controls, have far too much play at the lever. Incredible seeing as this is by far the easiest adjustment on a bike. The makers even give you knurled adjusters so that you don't even need any tools, and cover it adequately in the owners manual and yet...it's often neglected.
 

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I appreciate these so called "boring" posts. well written and clearly explained.

thankyou forchetto
 

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Excellent post! I have experience with the leaking neutral switch and its replacement. I found the electrical connector very difficult to get back on properly, probably due to the springy tension inherent in it, and the almost-inaccessible location. An angled long-nose pliers is helpful for this.

Also, be aware that some oil will come out if you remove the switch, but not as much as you might expect, maybe 100ml.
 

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Just so you know, whenever I see the words "boring" and "Forchetto" in the same post my CTRL-C keys begin to vibrate... and I can't blame them!

Thank you once again for the great information. +1 on the idea of the "Complete Forchetto Guide to Life on a Bonneville" I will be the first to line up for a copy :)
 

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Great post Dr. F.

Just for completeness, I will add further BORING facts (you have been warned).

The neutral switch goes to pin 10 on the ignitor/CPU/ECU. The Ignitor has to see this pin grounded in order to start. Officially that pin is called Ignitor Input Enable 2. Ground pin 10 and the bike will always start despite any problems with your neutral switch or wiring.

If you remember back when bike didn't have neutral lights (God Forchetto is old !), then you can disconnect that light and just ground Pin 10. You've just eliminated a whole lot of potential heartache and thumbed your nose at the nanny state.
 

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Discussion Starter · #13 ·
The neutral switch goes to pin 10 on the ignitor/CPU/ECU. The Ignitor has to see this pin grounded in order to start. Officially that pin is called Ignitor Input Enable 2. Ground pin 10 and the bike will always start despite any problems with your neutral switch or wiring.
Good idea, thanks. Better than just grounding the wire to the switch and have the green light constantly on as I've suggested. Edited post to include that.
 

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For the EFI models, at least on the mechanical speedo ones, you could disconnect the Black/White wire that goes to the ECU's pin A31 and connect that terminal to ground.
Thanks so much for this information Forchetto. My Bonnie is in the shop right now for some warranty work, oil seep from this sensor is one of them. My question is, if I don't care for the neutral light coming on, could I ground that Black/ White wire that's going into pin A31 and replace the actual sensor with a simple M10 drain plug?
 

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Discussion Starter · #15 · (Edited)
Thanks so much for this information Forchetto. My Bonnie is in the shop right now for some warranty work, oil seep from this sensor is one of them. My question is, if I don't care for the neutral light coming on, could I ground that Black/ White wire that's going into pin A31 and replace the actual sensor with a simple M10 drain plug?
I haven't tried that but sounds feasible. Looks as if you need to disconnect the wire that goes to the light otherwise it'll stay on.

Use a copper or alloy sealing washer on the blanking plug as well.

Here's the wiring diagram for the LCD speedo models, item 9 is the neutral switch:

http://www.telecable.es/personales/vacas/triumph/LCD/Wiring%20Bonneville%20LCD%20speedo_small.jpg
 

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Folks, class is in session. Dr. Forchetto's lecture today is...

Thanks again Forchetto, I really like your educational posts
 

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Discussion Starter · #18 ·

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Think I'm going to splice in a toggle switch between the Neutral Light Switch and the ECM. That way if the Neutral Light Switch ever fails, I can flip the toggle switch to ground the wire coming out of Terminal A31 and bypass the Neutral Safety feature. If it works out well, I may consider doing the same for the Clutch and Side Stand, as well. I think the most important thing is finding a set of good looking switches. Don't want my bike to start looking like a junkyard salvo ride.
 

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