The next step is to remove the head, so we can check the condition of the combustion chamber, the valves, the bores, and of course the pistons. Somewhere in here is the reason for the low compression in the right hand cylinder, it is just a case of checking out the parts as you see them.
The valves seem fine, and have no leaking, so that really only leaves the piston or rings.
Now we get the heart of the matter, the first look at the bores, and piston crowns, there was a fair bit of carbon build up, which I have started to clean off the pistons. There is slight scoring in the bores showing signs of previous trouble, a minor nip up, or a ring broken in the past.
A65L barrels and pistons
The barrel just needs a light hone, and will be good to go, the piston crowns show +20 so there was a past problem hence the signs of previous scoring, and with the barrel removed we find the cause of low compression, the rings are all stuck solid in the right piston, nothing too major then.
Stuck rings = low compression
Right time to strip and clean all the parts, hone the barrels, new piston kits, valves, valve guides etc, and start building it back up.