Kohler cv22 keeps breaking rocker arms after rebuild

[monster318]

Hello. I was gifted a Scag Super Z with a 22hp Kohler command engine that had a cylinder 1 blown head gasket. (Was burning oil very badly). So as a precaution I put a whole new head with all new valve train on that side. Also as a precaution I removed the valve cover from the cylinder 2 side and looked everything over including taking the rocker arms off. When I deemed everything on that side visually appeared okay I went to put the rockers back on. On the exhaust side the bolt stripped out of the head that holds the rocker down. So I put a Heli coil on both the intake and exhaust rocker bolt. Reassembled everything and thought we were good to go. Once I got the motor running everything was fine. The very first time I mowed with it, on the second pass maybe about 15 minutes into mowing it POPed and after some investigating I found exhaust rocker on cylinder 2 broken in half. I had an extra on hand from the cylinder 1 side that I had replaced. So I installed that. Now after about 2.5 more hours on the clock it broke that same rocker again in the same way.

The motor doesn't knock or tick or anything it shows no sign before it breaks it just goes POP and that's all she wrote.

What could be causing this??

 

[CalG]

Hello. I was gifted a Scag Super Z with a 22hp Kohler command engine that had a cylinder 1 blown head gasket. (Was burning oil very badly). So as a precaution I put a whole new head with all new valve train on that side. Also as a precaution I removed the valve cover from the cylinder 2 side and looked everything over including taking the rocker arms off. When I deemed everything on that side visually appeared okay I went to put the rockers back on. On the exhaust side the bolt stripped out of the head that holds the rocker down. So I put a Heli coil on both the intake and exhaust rocker bolt. Reassembled everything and thought we were good to go. Once I got the motor running everything was fine. The very first time I mowed with it, on the second pass maybe about 15 minutes into mowing it POPed and after some investigating I found exhaust rocker on cylinder 2 broken in half. I had an extra on hand from the cylinder 1 side that I had replaced. So I installed that. Now after about 2.5 more hours on the clock it broke that same rocker again in the same way.

The motor doesn't knock or tick or anything it shows no sign before it breaks it just goes POP and that's all she wrote.

What could be causing this??

A rather uninformed guess on my part, but.. "valve striking the piston?".

It shouldn't, but it could be the rocker failure is a symptom of a timing gear failure But, the engine should not run well if the cam drive is off, you would notice.

 

[stuckmotor]

I'm thinking that if you accidentally switched the intake and exaust rocker arms after the initial inspection, it might have made a difference.

 

[monster318]

I'm thinking that if you accidentally switched the intake and exaust rocker arms after the initial inspection, it might have made a difference.

That would be a possibility, but when I did cylinder one side, I ordered what Kohler called a "valve train kit" which included- new rockers and bolts, push rods, valves, springs, seals etc. besides the valves nothing was marked intake or exhaust to indicate which one it should all go on. So I assumed everything was the same. Also nothing looked to be different between the intake or exhaust side on the head. So I wouldn't think cylinder two would be any different

 

[DLTTrekkers]

Valveguides to long ?

 

[445A]

I have seen this happen quite frequently when the top rpm is above 3600. Use a tachometer, not your ear. I've been in small engines for 30+ years and can tell if it's over reving, but can't tell by how much. Kohler governors seem to slip and start slowly climbing up in rpms. I can assist you in the adjustment procedure if your not familiar with it.:tractor: