Changing the Fluid in your ZA50 is not very difficult. You will need a good flat head screwdriver and a 22mm (7/8") end wrench or socket attached to your favorite ratchet. (01.) Warm up the engine. (02.) Remove the rubber filler plug from the top of the case. (03.) You will need to put the Puch up on the kickstand or suspend it from a lift. Make sure the engine is level. (04.) Place a drain pan under the engine case beneath the drain plug. (05.) Remove the drain plug from the bottom of the motor with the 22mm (7/8") socket or end wrench. (06.) Grab a smoke or a beer as the fluid drains. (07.) Replace the drain plug in the bottom of the engine. (08.) With a flat-head screwdriver remove the side cover oil level plug (cheese head machine screw). (09.) Add approximately 9.5 oz. of fluid until it just begins to overflow the side cover oil level plug. (ATF type F is recommended by the manufacturer) (10.) Replace the side cover oil level plug and the filler plug in the top of the case. (11.) Blast and enjoy.