# Kohler Command Pro "A" & "B" Style Pistons



## Bob Driver (Nov 1, 2017)

I really like the Kohler Command Pro Series of engines, but they can bite you in the wallet when it's time to do an overhaul. What you need to understand is Kohler did a design change to the pistons, so you can either have "A" style, or "B" style pistons, depending on the age of the engine. The "A" style pistons ran a 1.5mm thick top ring. The "B" style pistons run a 1.2mm top ring. The "A" style rings are NLA (no longer available) and the readily available "B"style rings won't work on the "A" style pistons.

You don't really know what you have in the way of piston style until you tear the engine down. If it's "B" style pistons, the OEM rings are about $40 a side. If it's "A" style pistons, good luck finding the rings and you'll probably end up buying "Piston Kits" ("B" pistons & rings) at $140 per side. Here's a look at both piston styles so you know what to expect. Don't shoot the messenger, Kohler didn't even ask me for my thoughts. Besides, you end up with a matching set of "A" style Kohler pistons you can use to make some really cool, but expensive, door knobs for your shop

A Style Piston









B Style Piston


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## stevehoskins65 (10 mo ago)

I used Hastings 5032 they worked perfect, 1.5 top and middle 3.0 oil 80mm bore.


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## Bob Driver (Nov 1, 2017)

stevehoskins65 said:


> I used Hastings 5032 they worked perfect, 1.5 top and middle 3.0 oil 80mm bore.


I heard about doing that at Kohler Service School, but I also heard from the Instructors that the ring profile is not the same. The OEM 1.5 top ring is "rounded", OEM middle ring is "Stepped" with the step to the bottom. Lil Red Barn also sells the standard 80mm A-style piston rings, if you can find them. The Kohler CH/CV V-twins came in three different bore sizes...... Wear limit to oversize is .05mm

77mm -- 18, 20, 22 HP.... CH/CV 18, 20, 22, 620, 621, 640, 641
80mm -- 22, 23 HP.... CH/CV 22, 23, 620, 640, 670, 680
83mm -- 25 HP.... CH/CV 25, 730, 740, 750


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## stevehoskins65 (10 mo ago)

Not sure if the rings I replaced were OEM but the Hastings rings were identical not rounded or step, but I didn't buy the mower new.


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## Papaw's Repairs (9 mo ago)

I've seen those pictures of the pistons before, not sure what engine they come out of, I think a single cylinder. I've been using the B style in place of the A and the pistons don't come all the way to the top of the cylinder. There shy about 1/8 inch . They still run strong


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