Yamaha Neos 2 Stroke Trouble Starting

Hi guys so Ive practically completely rebuilt my neos from the ground up. New electrics, new variator, new stator, new exhaust, bigger 17mm carb and an apirilla 69cc bore kit. I've had it in pieces to clean and paint body parts for the past few weeks and gradually parts have arrived and the ting ran great until I installed the bore kit and new carb and now it wont start. I'm thinking its the plug because it only just protrudes out of the cylinder head into the barrel and the old cylinder head was longer. I have done all the usual checks and it sparks well etc and there is fuel going into the carb so it must be the length of the plug right??