How can I determine whether my piston is reusable so as to replace just the piston rings?

1st groove: Compression Ring
2nd groove: Stepped Scraper Ring
3rd groove: Slotted Oil Control Ring

The most common problem of a piston that needs replacement is in case there are scratches on its body.

What other parts I may need to replace when replacing the piston rings?

To replace the piston rings you need to disassemble the engine, so you also need to replace the cylinder gasket.

$28.98

In stock

Piston Ring Set for KOHLER K90 1500 Watt Models, K91 (2.395") .020" [#220803S] and related spare parts.

This listing is about a brand new after-market top-quality Piston RingTips for safely installing piston rings Set made by the well-known OEM firm CABER, and fits the following KOHLERSpare Parts for KOHLER engines models, and replaces OEM Part #220803-S:

This Piston Ring SetTips for safely installing piston rings has diameter 2 3/8" + .020" (60,83 mm) Oversize and consists of the following piston rings:

Our Piston Rings are branded and come directly from the top-quality and worldwide-known OEM Manufacturer CABER.
CABER Piston Rings are made from I-Cast Iron with high bending strength according to ISO STD 6621-3:1990 and DIN 70909.
Protect your valuable machine. Use only Branded & High-Quality Parts. Enjoy thousands hours of safe and trouble-free operation!