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Here is one that has had me scratching my head it may be a normal issue I don't know.
When I rebuilt my 1978 R80/7 there were a number of electrical issues that needed attention and all I thought were done but when I pull the clutch in and put the bike in gear the neutral light stays on and goes out when the clutch is let out is this normal, it comes on again when I pull the clutch back in to change gear.

I fitted a new neutral switch to the gearbox and also a new switch to the clutch lever, also replaced the starter relay and its socket on the frame as it was rotten and contaminated with brake fluid.

If it's normal then fine I will just live with it if not it would be nice to know where I went wrong.

Certainly not normal for the light to work that way. For me on my /7, at idle engine running with my hand off the clutch lever, the green light is on. I pull the clutch lever in to change gears, the light goes off. OK, I'm not sure if I just pull the lever the light goes off, but definitely once I've snicked the foot lever, the light goes out and I never see it again until I'm back at idle and in Neutral.

Note there are two types of sensors for the neutral light. They are "innies" and "outies". I forget which year they changed...something like 1975 or so??

Kurt

As Kurt says, there are two types of clutch switch (for five speed gearboxes). One is on when the plunger is pressed in, the other is on when it is released. Needless to say, the actuating cam inside the box is also different. It seem more than likely that you have the wrong switch for the box (or the wrong box for the switch)... this is about the only thing that would explain your symptoms.

The only way forward is to remove the switch and check which way it goes then obtain the other type.

It's worth bearing in mind that the boxes around the change over date are otherwise interchangeable so the box in the bike may not match the machine year.

If you still have the old switch and it is still working, you might be able to get a clue from it... even if it isn't fit for re-use.

Rob

Thank you gentlemen never thought of that, the gearbox is original and I did replace the switch on the gearbox so it must be the switch but I thought I checked it was the same before I fitted it, when i put it in gear clutch engaged light is out, while in gear pull clutch lever neutral light comes on.

Diode on the back of the fuse block in the headlight is bad.

The starter is able to be engaged when either the transmission is in neutral or the clutch lever is pulled. The diode is there to prevent the power from the clutch lever switch to feed the neutral light.

My apologies, I think I may have misread the original post. The way I read it, the neutral lamp was working exactly opposite to the way it should be. Re-reading, I don't think this is the case... so

The correct function of the neutral lamp is that it should be on when the gearbox is in neutral and off at all other times. It should not come on with the clutch...

like so...

Clutch pulled........In (any) Gear.......Lamp off

Clutch pulled.......In Neutral............Lamp On

Clutch released....In any Gear...........Lamp Off

Cutch released.....In Neutral............Lamp On

If the neutral lamp is comin on when the clutch is pulled and when the gearbox is in gear, the implication is that the blocking diode in the starter protection circuit has failed short circuit. This diode is attached at the rear of the circuit board in the headlamp shell. There is good news... and there is 'not so good' news.

Good news...

A replacement diode is easily obtainable and will cost you a matter of pence, cents or whatever your currency is... source a small rectifier diode from an electronic component supplier. The one used by BMW is a IN4003 I think but any rectifying diode able to carry 1 amp (or more) and with a peak reverse voltage of over 200 volts will work just as well.

It is fairly easy to fiy it into place provided you have a suitable soldering iron and the ability to use it. I must be fitted the right way round but that is fairly easy to get right if you compare the new and the old.

Not so good news...

You have to strip all of the wires off the circuit board and remove the board from the headlamp to get at it. Take plenty of notes and images on how the wires connect and route.

Or. of course, you could just live with it...

Rob