I know on my TT S3 which came with a pull start I needed to lower the motor about 5mm so the flywheel would reach the starter box wheel as the rtr motor sat higher due to the size of the pull start housing on the back of the motor, needs to be no more than about 2mm in from flush to the bottom of the chassis through the flywheel cutout, not familiar with other buggys but something I would check first.