hi i finished a project bike i was doing a couple of weeks before christmas and it was running fine i went to start it yesterday morning and the engine sounded different, i checked to see if all the exhuast pipes were getting hot and the pipe out of the number 3 cylinder was cold any ideas on why it has developed this misfire it has all new plugs and was being started every weekend with no problems it has also become difficult to start from cold

Just a bit of speculation based on what you said, but if you have been starting it up everyweek, perhaps overuse of choke and not enough running at temperature has fouled up the plugs?

Have you took them out and give them a clean, especially the one not firing yet?

took the plug out last night it looked ok but gave it a clean anyway put it back in and now all seems to be fine, firing on all four again

stefan wrote:any ideas on why it has developed this misfire it has all new plugs and was being started every weekend with no problems

As Neo said if you don't let the bike get up to operating temp each time you start it you can easily foul the plugs which is probably what happened here (new or old plugs will die just as easily!).

When the bike is cold, start it using full choke and no throttle. If you use the throttle when the bike's not running you can also foul the plugs.

Good to hear you revived the plug, they don't always come back from the dead.