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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!

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.

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.

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?

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!

jallen2845 said:

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!

Click to expand...

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

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!

jallen2845 said:

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!

Click to expand...

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

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.

Rivets said:

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.

Click to expand...

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

Rivets said:

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.

Click to expand...

I thought about that to Rivets, but also thought that if they were on the wrong side the exhaust and intake ports would be upside down.

He has a compression problem. I have considered the timing is incorrect and the valves are opening and closing at the wrong time. but without the pushrods in place he should have compression, unless the fact the intake valve isn't opening and can draw in air there is nothing to compress.

I think if it was mine I would try a leakdown test and make sure there isn't a ring problem or some other problem causing lack of compression. After that I would be rechecking the camshaft timing.

Yes, I understand that it is unlikely, but on this forum and at the shop over the years I have seen very odd things. I agree that a leak down test would provide some answers and eliminate some possible problems. I would also try to figure out why the pushrods bent. I just had to replace a head where the valve guides came loose, not allowing the rockers full travel.

Alright guys, I think we have a winner. Please don't blast me for this, I feel like enough of a dumba$$ already! I came to the forum for help (as I have done with many things in the past) and I think you guys have helped me figure it out...but boy do I feel stupid. When I put the camshaft in, it never dawned on me about timing. I did not put the cam in the proper way so the engine timing is off. I have a basic knowledge of how engines work, and have worked on many aircooled VW engines, but like I said this is my first time inside a small engine like this. I just stuck the cam in there. Stupid me. That would explain the bent rod (possibly contributed to by not compressing the hydraulic lifters) and the lack of compression. The only thing that doesn't make sense is no compression with the push rods removed, unless as ILENGINE said, there is no air to compress since the intake valves aren't opening, and that sounds very plausible.

So...my questions now are:

1. This sounds like the answer, correct?
2. Is there a timing mark on the cam and how do I assure that it is in time when I put it in?
3. Do I need to order new headgaskets again or can I reuse the ones that I just bought and installed?

Thanks for all the help!

There is a dot next to a tooth or between two teeth on the crankshaft gear, and the camshaft gear. Line up the two dots. Since the engine hasn't been run, and if the gaskets aren't damaged I would try to reuse them.

Don't feel bad about the timing marks on the gears. I had a customer bring me a 5 hp briggs around 10 years ago that he had totally disassembled including removing the rings from the piston, and brought to me in a cardboard box. He was trying to find out why it wouldn't start and run. I had to reassemble the engine, install new gaskets, and find out cause of his starting problem.

Final cause of failure to run was a faulty spark plug.

I was going to vote for stuck valves, but mistimed cam apparently can cause the same problem. If the pushrod got bent on an engine just cranking over, there was an interference problem of some kind. A valve guide migrating out of the head, a sticky valve, or in this case, valve timing allowing the piston to cram into the valve are the likely suspects.
I would re-use the head gasket, torquing it in three steps to the final torque value, using the factory specified pattern. If none, do criss-cross on the bolts, walking up and down and side to side.
There will be a significant change in crankcase pressure as the pistons move in their travel. They will cause low pressure on the up(compression/exhaust) stroke and higher pressure on the down stroke(intake / firing). Twins can also cause the same thing with possibly more pressure if they are opposed and have opposite strokes.
That pulse is used by some makers to power the fuel pump. Older Kohlers used a lobe on the cam with a mechanical follower.
tom

Is is safe to assume that the only damage is the pushrod from it being out of time and that the valves and piston are ok? I will visually inspect when I tear it back down of course.

Check page 11.4 of this manual for help on the timing make alignment.

http://www.mymowerparts.com/pdf/Koh...d-CV17-CV18-CV20-CV22-CV25-CV22-CV23-CV26.pdf

If it is still apart, I would pull the valve that had the bent pushrod, and twirl it to see that it is not bent.
I would not re-use the pushrod. I know I cannot make one 'straight' even rolling it back and forth on a chunk of glass or steel. Any bend will be amplified when it is under load and cycling back and forth at 1800cps.
Meant to metion that the hydraulic lifters are supposedly the same as Chevy small block, but don't bet the payroll on that. In addition, a fully pumped hydraulic lifter should not provide excessive lift such that it will bend a pushrod. If it were full of oil, then the time it takes from assembly to installation should be long enough for bleed down to take place, and there is a pathway for oil to leak out the top into the pushrod as the lifter cycles from loaded to un-loaded. The load/unload will meter the oil fed to the pushrod as the internal piston moves that tiny bit and lets oil have an 'opportunity' to enter the internal chamber to take up any slack in the valve train.
tom