54 T rear sprocket from a honda xr 125 if anyone struggled to find a replacement like I did has a 16t front and sitting nice at 70 I have had 78 out of it don't think I'm guna get to much more but the power getting it there for a single cylinder is fast pulls strong also have fitted magnum brisk spark plugs gecko kevlar clutch for extra torque and michelin pilot street tyres runs and rides excellent and out perform most 4 stroke 125 out there!! I've also fitted a new exhaust not shown on this pic from a yammaha r1