Piston identification for ss80

[Hallj]

Hello,
I'm new to the forum, hoping I'm posting in the right location.

Need to rebore and replace piston in a C15 sportsman 1966
The piston does not have any info on the top of the dome but under is marked 16114, I would imagine this is std but I would like to confirm.

Next question is what would you suggest to fit as an oversize piston. She's only a weekend soft use bike so I will not be racing her up and down the street. Be good to get some advise.
Thanks for your time

[rhyatt]

The rebore size is dictated by how much wear there is in the bore.
Firstly , take one piston ring off carefully and place in the bore.
Use the piston to push ring down the bore and measure the ring end gap.
Push down a bit more measure gap and again push down and measure.
If the gaps are not widely out of spec , you may get away with a set of new rings and a quick whizz round the bore to declare it.
Usually , if there's no +020 or anything on the crown , then you're standard.
Try this 1st