i dont know if its true but i heard the yellow ones dont make as many rpms but they are able to accelerate a little better from what i have read the blue honda clones usually put out around 5200 rpms thats about the average from all of the clones except the yellow ones which according to the local go cart/atv shop only make an average of 4900 rpms but have a little more torque and a little more acceleration but this is also coming from a guy that wears sunglasses inside the shop 24hrs aday i dont have a problem with that but it is kind of wierd