well, if it's not shifting i'm not surprised you are only hitting 33. Remember that if you are using stock gearing, your accel is going to be slower and your top end higher with the larger diameter wheels. If you have tried loosening off the 2 speed screw, you may want to check if you have the clutch in the right way. Also, to check if it's shifting... Just hold it in the air and giver some gas. You will hear and feel the shift for sure.