Hello guys, I have a 2007 noname GY6 chinese scooter. I recently fitted my new 100cc big bore kit+big valve head ,but the scooter can't achieve more than 40mph. The same thing was with my old 70cc kit couldn't go over 40mph. I have a 17,5mm carb. The head is ported intake and the washer too. CVT is stock except 8g rollers.