You hit it on the head mxwrench, the reasion the same engine with puddy in and and one with out is the crank will be lighter thats were the extra paformance comes from the ultamate crank would be so light and supper blanced like most top of the line on-road engines. As some people have noticed over the last cupple of years this has been an added feature to some off-road engines blance of the crank to piston is critical in making an engine that kind on its parts like bearings and rods wile aheaving the rev harder and faster off-road engine are now starting to get to the point of paformance that then need better blanced cranks to acheave higher rpms for longer times and faster smoother spin up. I have run a sirio bk evo 2 engine with a sirio 21 wcr crank and the paformance difrence was instantly noticable it reved much harder but the bigest difrence was it got there quick and smooth. regards jeremy.