CPeppy

Kohler CV25 - bent push rod

Had a rocker arm split and push rod went through it and subsiquently cracked the guide and (etc...etc).
New #1 head and valves, valve train kit, bled the lifters as per service manual, now the other cylinder (never touched that side) keeps bending its intake valve push rod. It does it a short time after start up. Runs good for those few seconds and then loses a cylinder. It appears to be way too much oil pressure. But sure don't know why that would happen. You can watch a lot oil come out just when cranking it over. Even after switching lifters. Anyone seen or heard of this before..?

30yearTech

I doubt that this has anything to do with your oil pressure. I think you need to pull that head off and inspect the intake valve, possibly it's sticking in the valve guide, or there is excessive carbon build up and the piston is "kissing the valve". This is where I would look for a problem.

CPeppy

I appreciate the reply but that can't be it. The reason being it ran on that cylinder while the other was out of commission. And it runs good for that short while until the rod bends.

30yearTech

Well, you know your engine better then me I guess and you should know whats going on with your engine. I still think there is something restricting valve or rocker arm movement thats causing your push rod to get bent.

When you figure it out, I would be curious to know how the oil pressure is bending your push rods though.

cheese

It certainly can be the problem, and likely is. Especially if you'e been using the engine on one cylinder.

flopshot

don't think it's the problem, but i seem to recall Kohler calling for 10-30 oil and cautioning against straight 30w.

CPeppy

Could you 'splain' this to me.

Posted By: cheese It certainly can be the problem, and likely is. Especially if you'e been using the engine on one cylinder.

cheese

A valve is sticking or hitting something. Probably the former. Excess heat is normally what causes the valves to stick in this engine, especially the kohler command twins. The cooling fins around the cylinder commonly get clogged with grass when people don't maintain them, and the heat builds up. Before long, oil is cooking on the valve guides and the valve sticks, bending the pushrod. Engine cools down, things contract, and may or may not work again with a new pushrod. Working the engine on one cylinder will surely cause higher than normal operating temps on the operating cylinder, since it it working harder and cooling less (lower rpms from the cooling fan).

The oil pump is designed to work at full capacity. It's pumping all it can when it's running, so how can it start pumping even more than it was when it was new? And if it was, it still wouldn't hyper-extend the lifters because they are designed to pump up to a certain point and cease. Oil pressure won't cause your problem.

CPeppy

Finally got my mechanic to go back to this repair. It's been sitting on the back burner for a while. Put it back together same as he did before. It ran for a short time and then went down to one cylinder again. Pulled the covers to see which push rod bent this time. Found none. Now what..? Bled lifters again and let it sit till after lunch. We decided to run it with the valve covers off so we could watch to see what was happening. It ran flawlessly. Put the covers on, ran it around till it got nice and hot, still going great.
That was (is) a head scratcher.

30yearTech

Well you must have let the gremlin out when you ran it with the vlave covers off, glad its working again for ya!!

cheese

Sounds a lot like what happens with old gas. I've seen valves stick when using old gas, but they sometimes free up after being used a while and new gas gets run through. On the ones that did not free up, I found a dry gold/brown colored varnish or deposit on the valve stem that siezed. Every time I find this, it is accompanied by skunky smelling gas in the tank, so I'm associating it with the old gas.