Add to Cart Compare Quick view Kohler K90, K91 Piston Kit iSaveTractors MSRP: Now: $39.99 Was: New aftermarket Piston Kit for Kohler K90, K91 4HP Cast Iron Engines. STD Size Only Replaces: Kohler 4687401S MSRP: Now: $39.99 Was: Add to Cart Compare Quick view Qty in Cart: 0 Quantity: Decrease Quantity: Increase Quantity: Price: MSRP: Now: $39.99 Was: Subtotal: Add to Cart