does anyone know how to wire a cut off switch for racing? and i need help with wiring up so that i can start car in gear

If you want to start the car in gear just earth the neutral light (the wire that's connected to the green neutral dash light) to the chassis to give it a false earth. The only thing is that you'll have the neutral light on the dash all the time if you're using the bike clocks.
I have a switch in this wire on my steering column that I can just press and hold to restart in gear if I stall it.

If you have the ZX9 wiring and have shorted the clutch and sidestand switch you should be able to start in gear without touching the neutral light.

No that's not right. The neutral switch is a safety switch too. It has a little dimple in the middle that when in neutral allows earth to connect to the wire.
Thinking about it, I know that when you stall the motorbike you can just restart by holding the clutch in can't remember off the top of my head why it won't work on mine this way.

It works on mine Use the kill switch for a cut off.