Topic: Ch 25 bent push rod problem

[MowJoe]

I have a Ch 25 on a Exmark mower that started running on one cylinder I thought it may be the coil so I checked it out it was good. I removed the valve cover and found a bent push rod on the intake valve.
I removed the push rod and checked the valve movement it was free I removed the lifter and checked it also seems good. I replaced the bent rod with another one I had and reassembled the valve train.
I started the motor with out the valve cover on and it started running on both cylinders. When I started to rev it up a little the intake bent another rod. Now I'm back to the beginning and have no idea why it bent in the first place. If any one has any ideas please let me know
Thanks Joe 

[2nstoys]

Check the valve guide. May have moved up like the Inteks do.

[Burwell555]

What did you set your valve lash to after putting the new push rod in?

[MowJoe]

Checked the valve guide it's tight. There is no valve lash it has a hydraulic lifters. It has to be binding somehow. Has anyone ever seen the rocker arm wear out and  cause binding that is the only thing I can see that looks like it has wear on it. 

[fx28]

You possibly have a lifter problem. The Kohler lifters can become sticky, most of the time it is from the type of oil used. I recommend using the kohler 10w30 oil. It has the additive package designed for the aircooled engine temps and makes the lifters much happier. If the oil does not take care of it you will probably need to change out the lifters.

Chuck Miller

[birdman_express]

We had a Kohler at the shop, and it bent push rods.
they were pumped up, and we had to turn the motor by hand,
til you had top dead center, let it sit overnight, then do the other
cylinder the same. Fixed the bending pushrods.

[MowJoe]

We had a Kohler at the shop, and it bent push rods.
they were pumped up, and we had to turn the motor by hand,
til you had top dead center, let it sit overnight, then do the other
cylinder the same. Fixed the bending pushrods.

So what your saying is the lifter can pump up to the point of bottoming the spring and cause the bending of the rod?
I picked up new lifters rods and rockers today I hope it works.
I've worked on these engines since they came out and just when you think you have them figured out you see something new. 
I called the customer he did use different oil on his last oil change he said it was 20w40 I think we may have a reason why it did what it did
I'll let you know what happens tomorrow

[birdman_express]

So what your saying is the lifter can pump up to the point of bottoming the spring and cause the bending of the rod?

The piston was tagging the valve, because there was not enough clearance. .....
because of the pumped up lifter. When we let the lifters settle overnight, it
busted right off, and purred like a kitten.

[gtpuller]

The piston was tagging the valve, because there was not enough clearance. .....
because of the pumped up lifter. When we let the lifters settle overnight, it
busted right off, and purred like a kitten.

 
Marc, is this a common problem in the twins and if so does it translate to a problem with the single?

Thanks

Tim Johnson

[birdman_express]

I haven't worked internally on many Kohlers, this was just one deal,
but this is what we were instructed to do, and it worked.

[gtpuller]

I haven't worked internally on many Kohlers, this was just one deal,
but this is what we were instructed to do, and it worked.

Thanks Marc

[MowJoe]

I have no signs of the valve hitting the piston.  The piston has a nice film of carbon and the valve also shows no signs of hitting the the piston.
I still need to put it together tonight and see what happens

[fx28]

We have had several issues with the hyd lifters over the years the command has been produced. From starting them up out of the crate to having 1000 or more hrs on them.  As Marc says they are pumped up or stuck causing your problem This might sound cliche' but using the Kohler 10w30 spec oil is what we have had the best results with making happy lifters.
  gtpuller, the singles use the same lifter, for performance apps most builders swap them out for solids with  reground or billet cam

Chuck Miller

[MowJoe]

I replaced the lifters and push rods with new ones and changed the oil customer used it the rest of the season with no problems. Thanks for the replies
Joe