More than likely the pins stuck in the piston , as well . in my limited experiance .
C R C / Crock Pot , Heat . 22 G wire hooked at the end , a small ( thin ) allen key
& check , or get , the rod fore & aft-ing on the wrist pin , is a start .
Engines that have been sitting about , the wrist pin is usually gungy.
Can take repeated attempts / heat cycles etc to free off & remove .
Found the HEAT GUN is vastly superior to boiling water , so getting that aimed up in there might save a good deal of aggravation .
Brett'll have a fit , but I put a wire thru the pin , degunge briefly with spinning across 320 paper , then polish on 600 S paper .
some'd use 1200 etc .The green 3 M pot scourers are good , A bit used & theyre softer for polishing ,
Cut in say 3/16 strip & pull / screww thru gudeon ( wrist ) holes in piston - to delacquer the build up there .
Obviously if youve got a good cleaner set up , and the patiance to wait it out , it'll save a good deal of hand work .
the object is clean & delacquered, everywhere . (in Ring groove too ) .
Deburring , polishing etc is the fancy pants stuff . If youve got a polishing wheel , the crank & pin , wrist pin etc , could go ' mirror finish ' .