MY MATES SONS GSX 400 (94) HAS STOPPED WE CAN'T GET A SPARK. CHECKED THE PLUGS AND CHANGED THEM CHECKED THE IGNITION PICK UPS.. VOLTS GOING DOWN READ 6.8 COMING BACK UP READ 5.8.. NOT SURE IF THIS IS WRONG OR RIGHT.. BATTERY GOOD. TWICE WHEN HE HAS TURNED IT OFF IT WOULD NOT START AGAIN, WHEN SHE WAS RUNNING HE HIT A SMALL BUMP AND THE BIKE DIED, COULD IT BE THE C.D.I UNIT? OR IS THERE ANY LIKELY SIMPLE PROBLEMS WITH THESE BIKES? ANY HELP WOULD BE VERY HELPFULL KIND REGARDS MARTY

Just a thought, have you checked all the fuses are located correctly and connectors are all mating. CDI units do fail and there's no way of testing it at home, all you can do is check for supply voltage 12V, ground or negative bonding (using an ohm meter/multimeter) check for varying voltage from ignition pulse generator, finally check voltage at the coils, you should expect to see a fairly high voltage 11-12V. Not sure where you would get one as it's quite a rare bike, a Suzuki dealer would be your best bet, maybe a GSXR400 one will work but don't quote me on that.

I BOUGHT A GSXR 400 GK73A NON RUNNER AS THERE WAS NO SPARK THE CDI WAS FAULTY REPLACED IT AND AT THE SAME TIME GAVE IT A GOOD SERVICE AND CLEAN IT WONT START AND THE CARBS OVERFLOW THE PLUG WIRES WHRE OFF I PUT THEM IN ACCOPRDING TO MANUAL WHICH IS LEFT COIL 1+4
ROGHT COIL 2+3

It is always the pick-up coils. If one goes down it takes the other with it. I specialise in the GSXR400 and have a supplier of parts in Japan. Anymore problems! PM me.