red cat 107cc in a 90 frame

[knuckelhead]

hey there new to the red cats. heres my prob, got this 90 from a guy that had probs with the charging. no biggy prob the stator. well got it back to gether and found that the batt was shot. would crank engine over when spk plug was out. had plenty of spark. when I put the new batt. in the thing cranked like mad but wouldnt fire.? comes down to it that I have lost all spark!? any one have a clue what I should be looking for? bad cdi, bad coil? all we did was put a fresh battery in it and the spark crapped out! Help!!! have a verry upset 6yo!!

thanks in advance