CB400F only running on 2 cylinders.

[Nurse Julie]

Just a thought, is your kill switch in the correct position, or a bit iffy, never known 4 plugs to give up working at the same time. 

[K2-K6]

You can jury rig a bypass to supply the coils direct.

Just take a line from battery + straight to the coil's supply input to try it. Make sure you just wrap it round the battery terminal so that you can pull it off in an emergency to act as a safety device (classic vintage hot-wiring  ).

If successful,  then you are looking at ignition switch/kill switch route.

It's not unknown for ignition switch contacts to play up on these bikes and can give you a dead stop.

[ka-ja]

It seems things are digressing, the initial problem ie 2/3 cylinders not firing, was certainly not a kill switch or ignition switch problem as that would have been all 4 plugs, so has something been disturbed while trouble shooting the original fault to loose all 4, unless the plugs were the counterfeits that are knocking about.

[Lobo]

Ian... you made me look up ‘Kettering’. Gadzooks there are some cunningly smart people about (Charles Kettering) - thanks!

[Riceman]

Great News!

The bike is running  , I fitted a new battery and plugs and she started first time. Im feeling very relieved that it wasn't anything serious.

Thanks once again everyone for your help and advice.

Andy

[Rob62]

Great news!! and a reminder to always check the basics first and avoid snap-diagnosis..