I just looked up sprockets for the EX250 and PBI sprockets has the largest range; fronts are 13 - 18 teeth and the rears go from 33 - 60 teeth. what I am wondering is will the EX250 accept a bigger than 15 tooth front sprocket without having the chain/sprocket contact the case? for the rear going from 39 teeth to 33 teeth is a 15% reduction so 6500 rpm will be reduced to 5500rpm if you can add a 16 tooth to the front then an other 6.6% rpm reduction drops the rpm down to 5150rpm at 70 mph. at this point the full benifit of the aerodynamics will be achieved.
|