CB400 only firing on one cylinder

[frogdon]

The plugs are dry, but slightly blackened. They've done it again since I last posted - I've now been riding my 125 for what feels like years

Cheers for the response tho

[nictecninja]

Don't want to sound daft,
But have you checked that you have the right grade of plugs fitted & checked the condition of the airfilter & that the air box intake isn't blocked or squashed.
Failing that some dirt/muck/rust/varnish in your jet's/passage ways can course rich running.
But you must understand that to use the colour of your plugs (plug chopping) as a indicator of how an engine is runing is hit & miss.
You need to get the engine fully of choke & then take it for a good long run 20 miles or so at sustianed highish rev's 7000+ to burn off the soot & colour the plugs nicely.
ie: a short blast down a nice A road or motorway, Not short start stop run a round your local village or town.
Hope this helps Paul.

[nictecninja]

Don't want to sound daft,
But have you checked that you have the right grade of plugs fitted & checked the condition of the airfilter & that the air box intake isn't blocked or squashed.
Failing that some dirt/muck/rust/varnish in your jet's/passage ways can course rich running.
But you must understand that to use the colour of your plugs (plug chopping) as a indicator of how an engine is runing is hit & miss.
You need to get the engine fully of choke & then take it for a good long run 20 miles or so at sustianed highish rev's 7000+ to burn off the soot & colour the plugs nicely.
ie: a short blast down a nice A road or motorway, Not short start stop run a round your local village or town.
Hope this helps Paul.

Go on go big 'n' rag it!

[chricol]

I've had a superfour for some months and I fried the plugs once just by being starter happy while it was sitting in the garage. The dealer i bought it from told me that I should not start it and switch it off after a few seconds idling but rather start it and drive off immediately after taking care not to rev it above 4500rpm before it warms up. Apparently CB400 plugs are very sensitive and they will be ruined if you just start it and switch it off a few times every day just to hear it idling