- check your piston to cylinder clearance...if its 0.10mm or more its too much
- decoke the piston including the ring grooves and make sure the oil relief holes arent blocked
- check the piston for damage...pitting, cracking, scoring or broken sections in the crown, ring lands and skirt
- if you have your cylinder off, after cleaning the piston and rings put the rings back on the piston, invert it and slide back into the bore...stand over a white surface or light box...you will see if there is a gap anywhere
- the oil expander rings also have a tendency to compress...you can retension them if youve got 3 hands...this wont work if you have too much piston to bore clearance
-need a 75mm pipe or old piston...oil the outside surface
-slide the expander ring over the outside surface
-hold one end to the surface
-hold the middle against the surface-no gaps
-pull the other end towards the fixed end..ie. stretch it slightly...you only need a few tenths of a mm...when you refit the piston into the cylinder they will come to a natural balance