Hello, I just picked a 1985 K100 Standared, I'm having an issue with the Neutral light not working and i just installed a new gear indicator switch but still no Joy as yet.

Welcome to the forum, good to see you along.

I know it might be the obvious but.....was it a new gear indicator [GPI] switch? They do go faulty. Only other place I can figure is blown bulb or the connection on the other end of the wire but someone else will come along with more information.

With no neutral light you must pull in the clutch lever to start the bike.

Yes it's a brand new one from the dealer. The old one was cracked and the springs had disintegrated. I figured just stop with the new one.

The connections inside the cluster on the GPI circuit board do get corosion and need resoldering sometimes. I cant be any more specific than that as I have never had to do one.

I will give it a look over the next few days. Thank you so much for your help. I copied some wiring diagrams to aid in my troubleshooting.

BMWRIDER275 wrote:I will give it a look over the next few days. Thank you so much for your help. I copied some wiring diagrams to aid in my troubleshooting.

Welcome - sorry, I didn't see your post earlier in the week! 

Not quite sure why your forum name is a full email address, but bearing in mind any old non member can access the forum as a guest through the dear old www, you could get unwelcome email and spam (rather than genuine, helpful advice and banter from forum members). My advice would be to go into your profile and perhaps remove everything after the "@". Changing your name is possible and immediately changes it on all your posts so protecting your identity. When contacting other members for meet ups, buying/selling spares etc., then contact is done by Private Message (PM) which is personal to you and the other member and can't be seen by other members/guests. 

Anyway, enough of that back, to the problem in hand - You may find the following link helpful with your trouble shooting:

https://www.k100-forum.com/t10495-gear-indicator-board-for-1985-k100rt-instruments#124102

The easiest way to determine if it is the new GPI switch or the GPI LCD or even the green neutral light that is duff is to test from the connector on the right hand side of the bike (near the fuel pump connector and rear brake light connector). 

If you separate the plug and socket, you can test the LCD and neutral light by connecting the various pins to earth (see the link above for which pin does what). Pins ABC all connected to Earth should give you "0" on the LCD and a Green neutral light. If you get just the "0", then it is likely the neutral light is blown (instrument cluster needs to come off bike, back comes off and you can remove/test all instrument bulbs while you're in there). If you get neither the "0" or the green light, then it suggests that the problem lies with the LCD circuit board. 

If you get both Green light and "0" indication, then your problem lies with either the connector (clean up plug pins and socket) or the GPI switch. Again, as detailed at the link, you can check the output of the switch in each gear (1-N though 5) by checking for continuity with a test meter connected to the various pin combinations. It is entirely possible that the switch is OK (and it should be) but may be misaligned by a small amount and therefore not giving the reading it should do to correspond with the gear selected - this was the problem I had. Realigning my switch solved the problem (PiTA to have to strip down the back of the bike again though) and it has worked perfectly ever since.

Good luck

More GPI info here:

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/gpi/gpi.htm

Thanks guys, this is great I'm sure with the info provided I'll have this licked tomorrow. I will report back with my results. thanks again you guys are awesome.