22-09-13, 11:35 PM
If number 3 chimes in once the throttle's opened up, then it's probably a blocked slow jet.
There are other possibilities though: that carb could be flooding or starved of fuel- fairly easy to test for with a length of plastic tube attached to the drain to check the fuel level.
Of course, if it's not sparks or fuel that are amiss, the other thing is compression.