I have removed top end from the engine. What I've found:
Compression ring - end gap 0.95mm (service limit as per manual = 1mm). Too close to limit.
2nd ring - end cap 0.45mm (1mm service limit).
oil ring top rail - end gap 1.80mm
that is too much I think?
oil ring bottom rail - end gap 0.4mm
Piston manufacturers recommend 2nd ring end gap to be larger than top ring. I've also read recommended oil ring end gaps to be ca 0.4mms.
Exhaust valves are not tight, one has small leak, the other has excessive leak.
Camshaft cam heights 0.8 and 0.7mms worn below service limit.
Rocker arm surfaces are worn.
Camchain is OK, 20 pitch length 128mms, service limit 129mms.
I'm afraid Suzuki does not sell +0.5mm oversize rings any more, only complete set with piston. The piston is still fine (cylinder was overhauled 10000kms ago). I've been looking through all piston manufacturers' catalogs but haven't found direct fit rings. There are some 105.5mm sets available but the heighth and width of the rings wouldn't match.