83 Suzuki lt125 four wheeler ignition problem

Sorry about posting this on a motorcylc group page, but their is no
four wheeler page. Anyway, I got this 83 suzuki lt125 four wheeler
from my uncle this past summer. He said it ran good and then one day
it died on the trail and hasn't run since. I tore the engine down to
find a broken piston skirt and a very wore out cylinder. I got all new
parts for it and had the jug bored out. Now I got it all back together
and I can't get it to fire. It's got excellent compression and I used
a service manual to set the timing so I know that's right. The funny
thing is when I pull the plug out it fires a weak but pretty
noticeable spark. When I put the plug back in though the engine
doesn't even think about firing. I'm guessing it just won't make spark
under pressure. To solve this so far I've replaced the spark plug (of
course) and the coil with brand new ones, but it's still doesn't run.
The four wheeler has a CDI box and an ignition stator. Could one of
those be the culprit? HELP ME!!!!