SOHC.co.uk Forums > CB350/400

CB400F only running on 2 cylinders.

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Riceman:
Update:
I have lightly cleaned the points and they are arcing when switching on the ignition so I assume that means they are ok. I traced the wires from the rear break light and found the earth wire was loose so have connected securely all other wires appear to be ok. I will try again once I have recharged the battery as it is very low on charge already, which makes me wonder if the battery could be the culprit :-\

ka-ja:
Your weak battery may be the cause, but only if there is a problem with the 2/3 coil or its circuit, have you checked if the 2/3 plugs are sparking when out of the head

Rob62:
If the motor starts and still only fires on 2 cyls, remove the points cover and run the motor briefly to see if there is excessive sparking from No2/3 points.... this would indicate a faulty condenser and would certainly cause a missfire... do it in the shade so you can get a good look at the sparking.

Riceman:
Update:

I tried starting the bike this am with a freshly charged battery and it would not fire up  :(
The unusual thing is that the coil which was cold yesterday is now warm to the touch and the other one which was warm yesterday is now cold  ???
Could this mean that my coils are both ok?
Confused or what  ::)

ka-ja:
Depends on which coil has a complete electrical circuit on the primary side with the engine not running as to which coil will warm up ie. which set of points are closed with the motor not running.
If you have the test gear, check the continuity and resistance of the coil/s low/high terminals and compare to specs, check you have a spark at plugs with plugs out of the motor

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