Emulate the "start in neutral" function of a K bike instrument cluster

[frankenduck]

This is handy if you're replacing the K bike instrument cluster with an aftermarket cluster but still want to retain the "start in neutral" capability of the gear position indicator circuitry inside the stock instrument cluster or possibly illuminate the neutral indicator on your aftermarket unit. (Of course you'll need to have a well-functioning gear position switch on the transmission.)

It's actually quire simple.  The way it works is that all three yellow/(other color) wires are grounded when the bike is in neutral.  When this occurs, the gear indicator circuitry in the instrument cluster sends 12v+ via the black/green wire to the starter button.  (The starter button also gets power when the clutch lever is pulled in and the clutch switch is activated.)

All you need to do is install three relays in series as shown in the diagram below.

In the diagram I've used standard Bosch relay terminal designations:

85: Ground relay trigger
86: 12V+ relay trigger
87: Output
30:Input

When all three of the relays are grounded by the three yellow/(other color) wires, power flows from the switched 12V+ power source at the top to the starter button at the bottom.

You can use standard Bosch style relays but those are rather bulky and expensive so if I were going to do this I'd do it with Waterproof Mini Relays

[frankenduck]

And the attached jpeg below shows you how to wire things up if you're using a third party instrument cluster and don't want the neutral indicator to light up every time that you pull in the clutch.

[rbm]

Thanks for the circuit schematic and detailed build Duck.  This is very useful when substituting the standard K-bike cluster with an aftermarket unit. The advantage for the builder is the simplicity of the design and ease of construction.

Building this circuit can be daunting for some people on this board and so I'm offering a short cut.

I have designed a printed circuit board to simplify the construction of the popular neutral detect circuit using four relays.  The board using through hole components which should be easy to source locally in a number of markets.  I was thinking of supplying this design in a flexible way, to meet different budgets and skill levels.

• A completely assembled and tested circuit (first photo)
• A kit consisting of the PCB and all parts ready to be assembled (second photo)
• The raw PCB

The board overall is 5cm X 5.2cm in size. It will take input from the TGPI switch and output a Start Enable signal and an active-low Neutral signal whenever the transmission is in neutral position.

[frankenduck]

Nice job. :2thumbup:  I'd be interested in getting one.

[gavthirtyseven]

Yeah!
Certainly interested in one for my upcoming racing brick project.
Waiting and watching with interest cool shades

[gavthirtyseven]

So if I bought this:-
http://www.ebay.co.uk/itm/140792721325?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
I'd need one of these?

[rbm]

That unit appears to be a tachometer and temperature gauge.  If you are going to keep the original K100 instrument cluster and ADD this unit to the bike, then this circuit card is not needed.  If you plan to eliminate the original K100 instrument cluster and outfit your bike with JUST this tachometer, then you will need this circuit.

[gavthirtyseven]

Great, thats what I figured.
All I really need from the instruments on a race bike is the Tacho, water temp, and the gear indicator is a cool bonus with the other features of your circuit.
So how do I get one.... :yes
- Boy am I grateful for websites like this and people like you, I can use a lathe and spin the spanners but I am a complete  :loopy: when it comes to electronics :dunno2:. Thanks. :2thumbup:   

[ekdave]

so did this make to production ? if so can i purchase 1 ?

thanks David