Yamaha G2 Compression

I recently brought a Yamaha G2 and it runs good but when I did the compression test. It showing between 85 - 90.

I haven't done the oil test yet to see if it the ring or value but I am wondering after I do the oil test and it the rings, should I just rebuild the cylinder and ring only or do the whole rebuild?

Whole kits seem to cost close to 300 bucks so I am not sure if it worth doing full rebuild or just piston/ring only or value only .

Feedback?

Thank you
Bill