Kohler SV830 Courage Pro 25 - pushrods, rocker arms fail...

[zuppamon]

I'm having trouble with my SV830, 10 years old, approximately 300 hours, well kept.
Was running bad last year, pulled spark plug wires & learned one cylinder was out. Compression test showed blown head gaskets.
While replacing valve covers, discovered both sides had bent push rods. Replaced head gaskets & push rods.

Ran great for an hour, then lost power again - pulled plug wires & learned that one cylinder was out. Pulled valve covers and discovered that one intake valve had poked through the rocker arm (pushrod pocket fractured and became a hole). No bent push rods. Looking at the valve guides, nothing appears to have moved. Bought 4 new rockers and will replace & try it again. If that results in bent push rods, then will replace heads and possibly lifters.

What happened and does anyone have suggestions?
Any way to test the lifters to see if the plunger is frozen?

Thanks!

 

[mechanic mark]

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[bertsmobile1]

Pushrods bend because some thing prevents the pushrod moving, just keep this in the back of you mind.
The usual reason for this is overheating which allows the valve guide to move in the head so when the pushrod pushes on the end of the valve the spring compresses as far as it can before the pushrod finishes pushing, so the pushrod bends .
After than , the No 2 reason is some thing on the valve stem ( rust or carbon ) preventing it moving all the way through the guide,
The next biggie is some thing inside the cylinder that hits the valve preventing it from moving

So unfortunately it is off with the head again.
FWIW, both valves are the same length and the guides are the same length and are pressed into the head the same amount so you can compare the position of the ends of the valves at TDC on firing stroke within a single head & between both heads to get an idea if a guide has shifted .

Wadda yer know just after I write this answer the very next new post had some pickies showing slipped guides so read the entire thread .
I have never seen a guide moved as far as the ones in the photo but they show exactly what I was trying to tell you above .bent pushrod thread .

 

[zuppamon]

Thanks for the reply...no sir, nothing looks like that as far as valve guides - the intake has a seal around it with a clip (like a PEX plumbing crimp), so it looks taller than the exhaust valve guides, but you cant see the guide because it's under the seal. Net-net, no guides look pushed up.
my valves are not rusty or bound, I checked for that when I replaced the head gaskets (unless they seize when it's hot for some reason).

The guy at the parts store suggested that one or more lifter plungers may be seized - is that possible?

 

[zuppamon]

Pushrods bend because some thing prevents the pushrod moving, just keep this in the back of you mind.
The usual reason for this is overheating which allows the valve guide to move in the head so when the pushrod pushes on the end of the valve the spring compresses as far as it can before the pushrod finishes pushing, so the pushrod bends .
After than , the No 2 reason is some thing on the valve stem ( rust or carbon ) preventing it moving all the way through the guide,
The next biggie is some thing inside the cylinder that hits the valve preventing it from moving

So unfortunately it is off with the head again.
FWIW, both valves are the same length and the guides are the same length and are pressed into the head the same amount so you can compare the position of the ends of the valves at TDC on firing stroke within a single head & between both heads to get an idea if a guide has shifted .

Wadda yer know just after I write this answer the very next new post had some pickies showing slipped guides so read the entire thread .
I have never seen a guide moved as far as the ones in the photo but they show exactly what I was trying to tell you above .bent pushrod thread .

I appreciate your response, but no dice, man (frustrated)...there really doesn't seem to be anything that would prevent the push-rod/rocker from moving.
After reading your response, I pulled the valve cover off and found bent push rod on the intake side
I then pulled the head off and removed the valve springs:
-The guides are the same length (photo attached)
-The valves move very freely in the guides
-The tappets move freely in their bores when you crank the engine over (intake travels further than the exhaust side, which I believe is normal).
-There are no scars on the piston or marks on the valves from hitting the piston
There is no visible reason visible for bent push-rods to occur - it only happens on the intake side
BTW, that's the valve seal sitting next to the intake valve in the photos.

Is it possible that I have hydraulic lifters and one or more of the plungers is frozen up in the lifter? I looked in the manual and they do not look like they're hydraulic, you set the clearance on them and lock the rocker arm nuts down with a poly-lock like you do with solid tappets.
Have any other thoughts?

 

[zuppamon]

I finally got this thing fixed - haven't had time to post.
You won't believe what the problem was. The valve guides and heads were fine, I'm glad I didnt go willy-nilly replacing parts.
The exhaust lobe on the left side cylinder was almost gone - enough to get the rocker arm to move, but not enough to get the combustion charge out. The intake pulled air a fuel in, but after spark, the gases had nowhere to go. I think the piston coming up for the exhaust stroke on a full/pressurized cylinder weas slamming the valve shut violently and bending the pushrod. This would happen religiously after a few second of run time. No mechanical interference anywhere.
Anyhow, I threw that Kohler Courage Pro in the trash and bought a new 27HP Kohler 7000 series as a replacment -my local Turf Depot has a kohler order coming, so they were able to add it to the order and I didn't have to pay freight. $935 out the door. It runs great and was a direct/bolt-in replacement. Hope to get at least 11 more years out of the mower now.

Thanks for your help and advice, guys!
Scott

 

[hlw49]

SV series engines aka Courage do not have hydraulic lifters. The only Kohler engines with hydraulic lifters are the Command engines,

 

[zuppamon]

SV series engines aka Courage do not have hydraulic lifters. The only Kohler engines with hydraulic lifters are the Command engines,

OK, not sure what your point is?
One exhaust lobe on the cam was almost gone

 

[hlw49]

For future reference

 

[zuppamon]

For future reference

Gotcha...wish there was a bolt-in replacement that had hydraulic. I am happy with this replacement and they say the 7000 series doesnt have as many problems as the older Courage PRO's.
for 950 bucks, it was a no-brainer to save a $4500 (sticker price 11 years ago) mower. I got a new PTO and flushed the hydros too. Hopefully, I get at least another 11 years out of it.

Thanks