hey guys im really very new to this so please if there is anyone that can assist me i would really apreciate it.
im from south africa and here the 400 is a trickey bike,i resently bought n gsxr400 gk76 with a 2nd gear problem ,but otherwise it ran fantastic ,got hold of a second hand gearbox and took the motor out to fit gearbox re install motor and hooked up all wires ,on the left side were the pickup is the gasket was leaking so i had to make new one little bit thikker then old one,tried to start the bike but it just turn the motor and there is spark intermittently.before that i could just touch the start button and it would idle,i changrd the pickup but still the same thing bike dont want to fire up,its really frustrating,is there any one that can assist me please
regards mikkie

How much thicker is the gasket? if it is much thicker it could move the pick up out of alinement with the trigger.

Have you got new spark plugs in .The guy in my local bike shop says 9 times out of 10 starting problems with these bikes is due to spark plugs.He was certainly right with my bike

i changed the plugs but still the same the starter turns the motor and it sounds like it wants to fire up but nothing at all.

Pull the seat off, check and clean all the connectors under there.
I had a similar problem on mine which turned out to be a connector that was corroded and covered in copper grease, so probably intermittently shorting/not connecting. Nightmare to find, but damn easy fix!