1979 ccm 500 Twinshock 4 speed 4 valve

1979 CCM 500 Twinshock 4 valve 4 speed
Hi... the bike was found in a barn a few years ago where it had sat for over 30+ years... since owning the bike I have gave it a light restoration frame was powder coated. tank painted. new rear shocks basically made it into a good running riding bike... I fitted a new electronic ignition... on starting engine I could see that there was a blow from the head gasket area upon removal of the engine and head I could see a chip of material had broken off the barrel liner... the piston and some valves look to be new... there is no damage to the head, valves, piston and crank all look in good condition but it will require a new liner for the barrel... everything is there for the entire engine. I understand this is a very sort after year 1979.