THE RATIO AS FIRST FITTED (FACTORY PRODUCTION) XL250 RF RE Front 13 teeth rear 38 teeth MTX200 (83-86) Front 13 teeth rear 42 teeth MBX125 F (84-85) Front 13 teeth rear 39 teeth XR250 R (86-87) Front 13 teeth rear 48 teeth MTX125 R (87-88) Front 14 teeth rear 40 teeth Technical advice: by changing the ratio the manufacturer recommends we get a different performance — a different behaviour — from the motorcycle. Higher top speed - fuel economy (suggested for touring). Fewer teeth at the rear. More teeth at the front. More acceleration - suggested for town. More teeth at the rear. Fewer teeth at the front.