You mean head and cylinder? A master cylinder controls the brake or clutch hydraulics in cars or motorcycles.
You want to compress the rings into the piston, slip the piston into the bottom of the cylinder(making sure the piston is in the right direction), slide the cylinder down on the cylinder studs on the motor (slide the cylinder down while compressing the rings with your hand. Once the piston is in the cylinder, insert the piston pin into the connecting rod and slide the head down onto the block. Be sure to use some two-stroke oil on the cylinder, piston and rings and the piston pin needle bearing.Go slow and be careful to prevent breaking the rings. And use new gaskets.
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