Mine did that! Check the spark plugs. And maybe get some ear plugs if it goes bang in a garage. My ears were ringing for ten minutes

dunkenb wrote:Mine did that! Check the spark plugs. And maybe get some ear plugs if it goes bang in a garage. My ears were ringing for ten minutes

You reckon it would be a good idea to keep trying to start it with the exhaust banging and possibly blowing back up through the carbs?

Probably not. Think it can damage the valves if you do it too much. Just losen the rad and stick some new plugs in.

Already put brand new plugs in there.

have you put the plug leads on the right way round?

Gonna make sure they are put on the right way later. Is coil 4 the one one the far right as if you're sitting on the bike or if you're looking at it head on?
Took the engine side case off to turn the crank by hand, after taking the spark plugs out. Engine turns ok. While the plugs were out I checked to see if they were still sparking ok again, now nonw are sparking. Will check 'em again later when I finsih work as it will be abit darker then....

Plug number 4 is the one on the far right as if you are sitting in the bike.

It sounds to me like you have a dodgy conection somewhere, it could be anywhere from plug cap, coil cap, the connecting wires on the individual coils or the 3 little wires that come off the coils and plug into the loom, check these last ones closely as they are really easy to trap and damage.

Thanks for that. Will have to try that tomorrow though as i've just got in from work.
If, say, only three of the spark plugs were sparking, would that be enough to start up the bike, or would it just ignite the petrol and bang outta the exhaust?

Yes, the unburnt fuel in the cylinder not sparrking being forced into the exhaust like it would do to the exhaust gasses usually, the hot gasses going into the exhaust from the other cylinders will eventually ignite the fuel in the exhaust causi g the back fire.