Kohler CV15 low compression:

17 years ago

Hi I picked up a Ransomes Bobcat 48" commercial walk behind recently with a Kohler CV15 engine. The engine started and ran well with no smoke as long as I gave it a shot of carb and choke cleaner first. A compression test revealed just 75 psi warm at WOT, so I pulled the head which was in remarkeable shape with new valves installed. I popped the valves and gave them a quick grind to check the seal, and reassembled the head with new springs and a new head gasket . Now the compression guage barely moves, and a leakdown test has mad air rushing past the intake valve. If I back out the fixed rocker stud bolt, the valve will close and seal tightly. Obviously there is a geometry problem but I'm not seeing it. Any takers?

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Comments (6)

bill_kapaun
17 years ago
OFF the top of my head, I think there is a leak down procedure for the hydraulic lifters.

It sounds like you have the lifter "bottomed out". and then when it starts to "pump up", it's keeping the valve from seating properly.

Download the service manual from the Kohler site.

http://www.kohlerengines.com/service/manuals/index.jsp
bushleague
Original Author
17 years ago
I have the manual on .pdf, Thanks, and performed the bleed down on the lifters prior to installation.
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tomplum
17 years ago
Did you mean that when you had gotten it, the head had just been re-done? If so, can you confirm the part#s they used? If all is as it should be, I'm thinking Bill is correct on the lifter issue. Remember they don't like straight 30W oil.
bushleague
Original Author
17 years ago
It's hard to tell if the head work was recent, the engine is just low-time I think. Guy used it as a backup machine and gave it to me when he moved to Charlotte with his two Exmark Lazers. Being notorious for losing head gaskets and breaking con rods, I figured I'd take a close look at this one before it goes on C.L.

I just rebuilt a CV20 twin with no problems.
I used a broken drill bit (I have many) inverted in the drill press in order to bleed down the lifters, and with the fixed rockers installation is a snap.
rcmoser
17 years ago
I have a couple of kohlers if I can get a hundred PSI of compression I'd think I had a race horse. I verily get 80 PSI when I check them, must be the hydraulic lifters bleed down as advised. On the other hand my vanguard has 160 PSI in each cylinders, so it must have something to do with the lifters. Mine don't smoke and run great.
bushleague
Original Author
17 years ago
Thanks to all who responded, it was a bleed down problem. I replaced the lifters, set it all up at tdc, and re-assembled the engine including new intake and carb gaskets, and ran it up. It runs quite well except I still need a shot of carb and choke cleaner on cold start. I adjusted the choke (automatic) full closed, and you can eat off of the carb. I'm staring at an FC420V that might fit in its place?