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Old 01-13-2014, 05:03 PM
homeowner72 homeowner72 is offline
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Kohler CH740 - No power under load

First post. Great forum here. I hope you guys can help out. I have been reading up a lot.

Engine:
1080 hrs (history unknown, but had a 2013 oil filter change)
CH740-0069
Serial: 3605912101
Build date: 02/28/2006

Small ride-on skid steer (Mertz/Boxer 427). Engine only drives a hydraulic pump.

Starts great. Hi idle no problem. When loaded up to the max pressure on hydraulics the engine seems to bog down and smoke a lot. This is when the governor is kicking in. For example when a cylinder bottoms out. Otherwise no smoke observed. Balloon over the dip-stick tube empties the balloon quickly at start-up and shows vacuum in the crank-case.

Fresh fuel
New plugs
New oil (10W30)
New oil filter
New air intake filter

Right plug is fouling. I was thinking head gasket, but with no crankcase pressure that is unlikely? There are also no external signs of leakage.
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Old 01-13-2014, 06:20 PM
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Is the plug gas fouled or oil fouled ?
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Old 01-13-2014, 07:34 PM
homeowner72 homeowner72 is offline
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Looks oil fouled. Very chunky. Like wet coal.

The location of the engine within the skid steer makes it really hard to check all but some elementary things. I can pull the engine, but then it is more difficult to test it under load. Even the left hand spark plug is already quite a chore.

I have removed he right hand valve cover and checked the movement of the valves. That seems fine. The top of the head looks like it just came out of the factory. Only a slight browning of the outlet valve spring and spring cups.
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Old 01-13-2014, 07:45 PM
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Landrus2 Landrus2 is offline
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Head gasket
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Old 01-13-2014, 08:07 PM
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Quote:
Originally Posted by homeowner72 View Post
Looks oil fouled.

That's a sign of blown head gasket between the cylinder and oil return port in the head, A compression test or better yet cylinder leak-down test will confirm before pulling the engine out......
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Old 01-13-2014, 08:14 PM
homeowner72 homeowner72 is offline
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Quote:
Originally Posted by Restrorob View Post
A compression test or better yet cylinder leak-down test will confirm before pulling the engine out......
I'll see if I can borrow a leakdown tester. Even getting the tester in would be difficult. I can just fit the plug it with the socket, but not with the ratchet. This is how little space there is.

Would a blown head gasket from cylinder to oil return not result in crank case pressure? And would it have such dramatic effect on the power at WOT when it runs great otherwise?

Thanks for all your help so far.
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Old 01-13-2014, 08:46 PM
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You can have those heads out in less than 30 minutes
It will be wise to do both sides .
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Old 01-14-2014, 12:21 PM
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Quote:
Originally Posted by homeowner72 View Post

Would a blown head gasket from cylinder to oil return not result in crank case pressure? And would it have such dramatic effect on the power at WOT when it runs great otherwise?

You need a water manometer to properly test engine vacuum/pressure, Yes a blown head gasket would cause lack of power under load..... Not to mention the oil fouled plug not sparking properly.....
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Old 01-14-2014, 01:18 PM
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Quote:
Originally Posted by homeowner72 View Post
Looks oil fouled. Very chunky. Like wet coal.

The location of the engine within the skid steer makes it really hard to check all but some elementary things. I can pull the engine, but then it is more difficult to test it under load. Even the left hand spark plug is already quite a chore.

I have removed he right hand valve cover and checked the movement of the valves. That seems fine. The top of the head looks like it just came out of the factory. Only a slight browning of the outlet valve spring and spring cups.
Some units can be a serious pain to work on in place. You may as well just pull the engine, you don't need to test it under load, what fer? Throw it on the bench, and do a leakdown test first! That will give ya a good idea what your up against.
You can download a manual from Kohler if ya don't have one.
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Old 01-15-2014, 10:12 AM
homeowner72 homeowner72 is offline
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Quick update: Pulled the engine out (1.5 hrs) and removed the head of the suspect cylinder. Head gasket had indeed failed. See photo. Failure seems to be at a very unusual location. The gasket feels like it has a bump, and there is a small fracture between lifter galley and the cylinder.

Do I need to change the valve stem seal while the head is out? Or are they typically OK.

Thanks everyone.
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