Everyone has there prefered method , the way I use is make a + sign from the solder . Place it on top of the piston so that the straight part is over the gudgeon pin from edge to edge of the barrel .refit head and gasket , torque head down . Turn kickstart very slowly untill the piston squashes the solder once . Remove head and measure the tips of the solder , 1mm- 1.2mm is ok .