Oversize engine rebuild kit for Kohler 624cc Command and Command Pro engines, cut for a finished bore of 77.75mm. Standard bore on these engines is 77.00mm. Fits CH18, CH20, CH22, CH620, CH621, CH640 and CH641 along with the CV equivalents CV18, CV20, CV22, CV620 and CV640, in each case where the cylinder has already been bored oversize. Kohler's oversizes on the Command engines are metric rather than imperial: what the trade calls .030 is 0.75 millimeter, giving the 77.75mm finished bore. The equivalent .010 and .020 sizes are 77.25mm and 77.50mm. Take particular care with CH22, CH620 and CH640, which Kohler built in both a 624cc 77mm version and a 674cc 80mm version; the model name alone does not establish the bore, and the spec number on the engine tag does. This kit uses Style A rings with a 1.5mm top ring. Measure the top ring from the old piston to confirm, since ring style follows the piston rather than the model number.
- FOR KOHLER 624cc COMMAND AND COMMAND PRO ENGINES ALREADY BORED OVERSIZE, finishing at 77.75mm. Standard bore on these is 77.00mm. Covers CH18, CH20, CH22, CH620, CH621, CH640, CH641 and the CV equivalents CV18, CV20, CV22, CV620 and CV640. This is a kit for an engine that has been to the machine shop, not for a standard bore.
- VERIFY YOUR BORE BEFORE ORDERING, AND THIS IS NOT BOILERPLATE. Kohler built CH22, CH620 and CH640 in TWO different displacements: 624cc at 77mm and 674cc at 80mm. The model badge will not tell you which one you have. The spec number on the engine tag will, and so will a bore gauge. If your engine is the 80mm version, nothing in this kit fits it.
- WHAT .030 MEANS ON A KOHLER COMMAND. Kohler's oversizes on these engines are metric, not inches. What the trade calls .030 is 0.75 millimeter, and 77.00 plus 0.75 gives the 77.75mm finished bore this kit is cut for. The same logic gives .010 as 77.25mm and .020 as 77.50mm. If the machine shop gave you a number in thousandths of an inch, ask them for the millimeter figure and match that.
- STYLE A, 1.5mm TOP RING. Kohler built these engines with two ring packages and the grooves are machined to match. Pull a ring off the old piston and measure it: 1.5mm is Style A, 1.2mm is Style B. Style is determined by the piston, not by the model number, so two engines with the same badge can take different rings.
- DO THE JOB ONCE. Hone the cylinders so the new rings have a crosshatch to bed into, check the rod bearing clearance and the crank journals, and fit new head gaskets and valve stem seals while the engine is open. Torque head bolts in sequence and in stages to your engine manual, and stagger the ring end gaps around each piston.