Yeah John,s right 100 to 150cc was 3 different classes years ago. If you want a 144 class, make sure you have after market 144cc mod. engines included. Then the engine builders will go nuts, with diffferent theries. I have a 04 cr125 2mm stroker crank, 2 mm overbore, carb borred to 40mm. Before the motor was decked,ported,40mm carb,icat, pc pipe,v force, I only rode the 144 a little bit, long story, but it,s way faster than the 37-38 hp motor. A mod 125 doesn,t stand a chance, around 20-21 lbs. of torque in a 144 mod. motor, touch the cluth and instant 20-21 lbs. of torque, if there,s traction 250f,s are kids play. hehe