[entwisi]

is it sparking? take the plug out, reconnect the HT lead and hold the screw part of teh plug against the cylinder using some insulated pliars( or even better if you can get it to rest there of its own accord without having to hold it. turn teh engine over and watch for a spark, it should be a nice blue strong one, anything yellow or just weak looking will not be good enough to run teh engine. If the spark is weak or not there, get a new plug, same again means the coil is suspect or its not getting a trigger ).

At teh same time as turning over above, you should see a slightly 'smokey' "puff" from the spark plug hole, this is petrol,and air at the perfect mixture so no ciggies! If its pure clean air then you aren't getting petrol, put your hand over teh hole and you shoud be able to smell teh petrol on it.