get a long 8mm bolt,a washer,and an assortment of small(1" and 2") peices of tube,the tube must be bigger diamiter as the wrist pin. put the washer on the bolt and a piece of tube and if u can find a bit of old tyre tube to cussion the tube against the piston.post the bolt together with washer,pipe,rubber through the wrist pin and screw the nut on the other end,be carefull that the nut doesnt scrape on the piston,and start tightening the bolt from the tube side,as the pin starts to come out u may run out of thread on the bolt so take it out again and put the longer bit of tube on,under no circumstances should u hit or shock the piston or pin or rod,you could cause more problems than u solve.by the way the nut and bolt i use is a metric thread,fits perfectly up to the wristpin without toutching the piston,i hope this helps u.