Replace the rings or new Barrels with pistons?

Pics from fuel pump side of engine




Barrel has no lip/ridge at the top

Clean it, check the gaps on pistons and if they are OK, change only piston rings.

Pete,
as well as checking the end gaps, also check the side clearance of the top two rings in their grooves, which should not be more than about 5 thou.
Judging by the amount of varnish and carbon below the oil control ring. there's been a fair amount of blowby going on...

ken

Someones been a bit enthusiastic with the 80 grit

I always give the top of the barrel a qick spin with the hone to highlight where the wear is. Most wear occurs in the top 25 mm of the swept area. As there isn't much left of the honing I'd say that they are probably on the worn side but its almost impossible to tell in a photo.

using your fingers holding the abrasive they follow the contours as they are soft. The stones on the hone buff the high points to a grey finish but the worn areas have the polished brownish finish

rebore& new pistons otherwise its half a job
i,m no expert though

given the relative cost of a new P&B set that's good advice

That's what I thought too. Actually, when I saw the pics I thought of hand honing

Rebore?
Only if you can manage to track down a set of those 0.5mm oversize Kolbenschmidt pistons...

ken

Id assumed that Ayjay meant barrel and piston set I found a set of oversize pistons got barrels machined to match to them, just need to source a ring set and its good to go! was it cheaper than a full set? If id had to pay for the pistons then no

by the looks of the barells and those pistons---
are well worn!(cream crackered infact)

any piston blow by is no good
it gets the oil all dirty and crank case pressure too