Check diagram, you are changing Gears C & D:
http://hondaspree.net/wiki/index.php5?t ... ion_Ratios
Remove Plastics, Exhaust and rear wheel.
Remove Belt covers and Clutch assembly
Remove gear cover
Remove old gears
Gear C is easily changed by hand
Gear D requires a hydraulic press to remove old gear and press gear D onto the axle
Remove all remnants of old gasket on motor and gear cover. Be sure surfaces are clean and smooth.
Re-install all gears into motor.
Be sure all Thrust washers are in place EXCEPT the one that goes against the gear cover on shaft C
Re-install gear cover with fresh gasket...the use of gasket goop is a personal choice.
Tighten gear cover bolts to proper specs and check to see if axle spins freely by hand.
Fill with recommended oil to proper level.
Check for leaks.
If spins freely and no leaks....reinstall clutch, belt covers, rear wheel, exhaust, plastics....BRAAAAP.