Hi all,

New to the forum and a bit of a newbie question here...

I've just rebuilt and un-seized a CB750 Kz 1979 DOHC engine - replaced items: new main cam chain, valves, piston rings, solenoid, spark units, coils, battery and plugs etc.

The starter motor is good, there's spark in each of the plugs, compression appears ok (will test once the kit arrives), I thoroughly cleaned out the carbs, but cannot get any of the cylinders firing!

Following the Service Manual when rebuilding, I aligned the no. 1 cam lobes towards the sparks and the alignment dots horizontal and the spark advancer to centre F I T

Coils are ordered - Left 1 & 4, Right 2 & 3

The coils have a yellow, blue and black wire - blue to left coil, yellow to right and black joining both b/w coil wires?

When I fill the carbs with Cold Start spray, the spray is igniting and flames shoot out the exhausts (no pipes yet), or if the choke is open, flying out the carbs!?!

Before I dismantle the entire cylinder head and rebuild it again - any advice on where to start checking would be greatly appreciated.

Thanks in advance for your help.