Help with Kohler CV740 after rebuild!

[jallen2845]

Hi all, I really need some help. I bought a really clean cub cadet gt1554 with a Kohler Command 27hp engine in it. The engine had 2 broken rods. I disassembled the engine and rebuilt it. 200 hours according to the mower. Found 2 broken connecting rods as suspected. Case was fine, pistons fine, rings within spec. I bought the parts and put it back together. I replaced the 2 rods, and the crank. New head gaskets, case (oil pan) gasket and put it back in the mower. It would not start and I suspected the carb needed cleaning, no idea how long it sat before I bought it. Anyway, it has very little (if any) compression. I can keep my finger on the plug hole while cranking it. I checked compression with a gauge and sometimes it goes to about 60 and sometimes its like 10-20. I can't figure it out! I pulled the valve covers and one of the rods was bent, it obviously wasn't bent when I put it back together. Valves looked good, and I verified movement of the rocker arms and valves opening and closing by turning engine over by hand. I pulled off all 4 rocker arms and took out the push rods and I still have no compression. Should I not have compression without the push rods in? Does that not eliminate valve or lifter issues? This engine has hydraulic lifters so no valve adjustment. Could the lifters be bad from sitting and that be what caused the bent push rod? But then shouldn't I have compression with the rods removed? Also, not sure how to describe this, but on the bottom of each head, under the valve cover, there is a hole, and compression comes out that hole when turning the engine over with the valve covers off. What the heck is that? I'm not an expert but this has me stumped. I used the book to reassemble. Do these engines have some type of compression bleed off or compression release? I just can't figure this out! Thanks in advance!

 

[ILENGINE]

You should have compression with the push rods removed, unless the piston is create a vacuum on the down stroke and you have no air to compress. The bent pushrod is most likely caused by the hydraulic lifters overfilling and can't compress when you turn the engine over. I always remove the lifters and compress them by wrapping them in a shop rag, and put a small socket in the open end and then put the whole thing in the vise to compress some of the oil out.

May try compressing the lifters and putting the pushrods back in and rechecking compression.

The air leaking from the bottom of the head might be where the exhaust manifold attaches. If air is coming out there with the pushrods in place then the exhaust valves are leaking. If it was doing it with the rods in place may of been the compression release.

 

[jallen2845]

Also, I did not put the lifters back in the same places, I failed to mark them. I did not drain them or test them, didn't even think about it. Could this be the problem? But shouldn't I have compression after taking all the push rods out? Thanks again.

 

[jallen2845]

The hole in the head I am referring to is under the valve cover. There is one in each head, in the bottom outer corner. I can't figure out what its for and why there is air (compression) coming out of it. How does the ACR work on these engines? Also what would cause the piston to create a vacuum on the down stroke?

 

[jallen2845]

I pulled the lifters and did as you suggested. Straightened out the bent push rod and put it all back together....same thing. No compression. I took off the carb and sprayed some starter fluid directly into the intake, nothing. It seems as if it is blowing out the intake, like the whole block is being pressurized? I am really stumped...thanks for the help and I welcome more feedback!

 

[KrashnKraka]

I pulled the lifters and did as you suggested. Straightened out the bent push rod and put it all back together....same thing. No compression. I took off the carb and sprayed some starter fluid directly into the intake, nothing. It seems as if it is blowing out the intake, like the whole block is being pressurized? I am really stumped...thanks for the help and I welcome more feedback!

That pressure likely equal to the suck and blow of piston bodies working and
nothing more, like simple displacement pressure?
The holes you describe are likely oil return pathways, the location reads as being
"normal design".
Absolutely no slight intended on your skill but seeing as how you write you did not
kmow about hydralic lifter installs I ask are you sure the ring gap alignment is opposed?
And head gasket/s is fitted correctly and bolts torqued as per instruction?

.... tap tap. Thinking.

KK

 

[jallen2845]

I did pay attention to the ring gap and torque specs. I have built air cooled VW engines but this is my first experience with a mower engine. The holes in the head likely are oil passages but it surprised me how much air came out them when I turned the engine over without the valve covers on to watch the valves. There was just as much pressure there as the spark plug hole. Strange. The head gaskets were labelled "top" so I don't think that would be it. I just don't get it! When I sprayed starter fluid in the intake while cranking it blew it back out. Its like something is pressuring the entire engine case. And the plugs have been bone dry every time I have pulled them out. I've verified I have fuel, and they were even dry after attempting to spray directly into the intake. Thanks again for the help and the ideas!

 

[KrashnKraka]

I did pay attention to the ring gap and torque specs. I have built air cooled VW engines but this is my first experience with a mower engine. The holes in the head likely are oil passages but it surprised me how much air came out them when I turned the engine over without the valve covers on to watch the valves. There was just as much pressure there as the spark plug hole. Strange. The head gaskets were labelled "top" so I don't think that would be it. I just don't get it! When I sprayed starter fluid in the intake while cranking it blew it back out. Its like something is pressuring the entire engine case. And the plugs have been bone dry every time I have pulled them out. I've verified I have fuel, and they were even dry after attempting to spray directly into the intake. Thanks again for the help and the ideas!

You have got no action happening in the chamber.
No fuel being sucked in , no exhaust pressure.
So the cycles are not building to compression.

This build is coming apart again,,, there is a major fault in the
assembly, somewhere. Wrong rings, wrong head gasket, valve
collets U/S.. could be anything along the line of chamber integrity
in failing to reach compression.

Questions.
Was it ever determined why the original rods busted.
Is it possible to video what you have as a cranking condition.

KK

 

[Rivets]

Are you sure you didn't switch the heads around, there is a cylinder #1 and #2. You must install the heads on the correct cylinder.

 

[KrashnKraka]

Are you sure you didn't switch the heads around, there is a cylinder #1 and #2. You must install the heads on the correct cylinder.

ummm...is it really that easy to confuse the install that way?
I would comment negatively on such a design 'fault'.

But that's me, in dino form - the KISS harpy:grin:

KK