Standard bore piston ring set for Kohler 674cc Command twin cylinder engines with an 80mm bore, replacing Kohler part number 24-108-26-S. This is the Style B set with a 1.2mm top ring. One set covers one cylinder, so a twin needs two. Kohler built these engines in two ring styles that are not interchangeable: Style A takes a 1.5mm top ring and Style B takes 1.2mm, and the ring grooves in the piston are machined accordingly. Measure the top ring off your old piston or look up the engine by its spec number before ordering. Note also that the CH620 and CH640 model names were used on both 624cc 77mm and 674cc 80mm engines, so the model badge alone does not establish the bore. For a cylinder already bored oversize, use the corresponding oversize set.
- FITS KOHLER 674cc COMMAND TWINS WITH AN 80MM STANDARD BORE, including CH23, CH670, CH680, CH620B, CH640B and the matching CV23, CV620, CV640, CV670 and CV680. Replaces Kohler 24-108-26-S. Oil burning, blowby out the breather and a dropoff in power under load are the symptoms that bring people to a ring set.
- ONE SET, ONE CYLINDER. Kohler packages these rings per piston, so a twin cylinder engine needs two sets. Order accordingly before you have the engine apart on the bench.
- STYLE B, 1.2MM TOP RING. This is a real distinction and it is not optional. Kohler built these engines with two different ring packages: Style A uses a 1.5mm top ring, Style B uses 1.2mm. The grooves are cut to match. A 1.2mm ring dropped into a 1.5mm groove will flutter and pump oil. Pull a ring off your old piston and measure it, or look the engine up by its spec number.
- CHECK THE BORE, NOT THE MODEL NAME. CH620 and CH640 were built in both 624cc 77mm and 674cc 80mm versions. The model badge will not tell you which one you have. The spec number stamped on the engine will, and so will a bore gauge. The 77mm engines and the 83mm CH25, CH730 and CH740 both take different rings.
- STANDARD BORE ONLY. This set is for a cylinder still at 80.00mm, within service limits and not bored oversize. Kohler's oversizes on this engine are metric, listed as .08, .25 and .50 millimeter, not in thousandths of an inch. If your cylinder has been bored, you need the matching oversize set instead.