weak spark

First try a new plug if it is not already, then try unscrewing your plug boot and cutting off some of the wire that connected to it. Cut about a centimeter in, evenly, to make sure you get a good connection, then re screw it back in. Your stator or cdi could be failing,or wires could grounding out somewhere but lets start with the easy stuff. LMK
 
If it was the stator, the whole system would be running low, so like dim lights and weak spark. You could test it with multimeter to see what its putting out for power, if it fluctuates greatly while idling or is very low then that could be the problem. And if it was the cdi then you would just have weak spark, not quite sure how to test the cdi tho
 
have you kicked it with the plug out, to see how the spark looks? If so whats it look like? And did you trim the end or the wire yet?