X-300 keeps bending Push Rods.

[Diggin It]

Just put in the third set of push rods in a Kawasaki 17HP FH451V (or is it 491?). Always on the right side (from the seat), never the left. Obviously something deeper, but what, and is it something I want to bother with on a 13 year old machine (DOM 083006) with over 1,000 hours?

 

[RandyT]

Pull the valve cover back off, and look at the position of the valve guide inside of the valve spring. I bet it has migrated toward the spring keeper, and is stopping the valve from fully opening causing the push rods to not be able to fully open the valves.

 

[Diggin It]

Hmmm, will see. Not sure exactly what to look for, but I can compare to the other side.

Couple of other notes:

The first time I had to do this a year or so back after losing power on hills, I found that one ear of the push rod guide plate was gone completely. No sign of it any where. No hole large enough for it to get inside either. Replaced that.

Currently, it has been audibly 'puffing' almost like missing or maybe an exhaust leak. This is both before and after the latest push rod replacement. Clearance is adjusted to .004 as spec'd. Or at least as close as I can.

 

[Diggin It]

Got about an hour or so run time before it ate itself again, so obviously there's something else going on. I'll check that guide spring in the next few days, but I'm thinking I'll let it sit for a few weeks until the weather is a bit less horrible.

 

[Kish318420]

I would look at everything on that side, replace anything suspicious looking or out of spec. Looking at it on the parts site (JD). I'm wondering about the rocker nuts and the screws in the end of them backing out allowing things to shift. Are you using any thread lock (Locktite Blue - semi) on those or a similar product? or even the studs those are screwed to?

 

[Amvcane]

Diggin it, I think RANDYT has a very valid point about the valve guides moving and restricting movement on the spring side of the rocker. The pushrod side will still move through its full cycle and will bend.
Here is a video of a Briggs with the same problem, different engine showing what to look for concerning the valve guides. Taryls camera man does a great poking around the engine. Kinda feel like you are in the shop with them.

How To Fix A Briggs and Stratton V-Twin Intek Engine That Is Running Badly (Bent Push Rod) - YouTube
You can start video at 4:50 mins. To skip the comedy.

 

[Diggin It]

I would look at everything on that side, replace anything suspicious looking or out of spec. Looking at it on the parts site (JD). I'm wondering about the rocker nuts and the screws in the end of them backing out allowing things to shift. Are you using any thread lock (Locktite Blue - semi) on those or a similar product? or even the studs those are screwed to?

Replaced the stud/bolt and nut this last time. Used LT Blue.

Diggin it, I think RANDYT has a very valid point about the valve guides moving and restricting movement on the spring side of the rocker. The pushrod side will still move through it's full cycle and will bend.
Here is a video

I'll look at that area next time I get a chance. I only do static images, no videos.

 

[RandyT]

Diggin it, I think RANDYT has a very valid point about the valve guides moving and restricting movement on the spring side of the rocker. The pushrod side will still move through itç—´ full cycle and will bend.
Here is a video of a Briggs with the same problem, different engine showing what to look for concerning the valve guides. Tarylç—´ camera man does a great poking around the engine. Kinda feel like you are in the shop with them.

How To Fix A Briggs and Stratton V-Twin Intek Engine That Is Running Badly (Bent Push Rod) - YouTube
You can start video at 4:50 mins. To skip the comedy.

Had seen 3 in the shop already this year. One on a Briggs intek twin which if you know anything about the engine will eat the pushrod and you retrieve it from the engine sump sometimes in pieces, sometimes wrapped around the camshaft. A Kohler Courage 27 HP and a Kawasaki. Problem is due to heads getting too hot and the aluminum softens around the valve guide and they migrate out toward the valve spring keeper until the interfere with the moving of the valve when it opens and then bends the pushrod.

 

[ruffdog]

So, the head gets real hot, valve guide then pushes out toward keepers, then, the guide won't push back in so easily, push rod bends?

 

[RandyT]

Certainly a valid cause, but I have to wonder if something isn't missing in this thinking. If a guide can migrate out on its own without any outside force, why wouldn't the valve keeper push it right back down at the same time? I would suspect that this happens on an engine when it is shut down. A guide moves on a valve that is closed. The head cools and locks the guide in place.

It probably does get pushed back in somewhat, but the guide will migrate 3/8-1/2 an inch in some cases before it contacts the spring keeper. I have seen them migrate enough that the guide is tight against the keeper and the valve will only move about 1/8 inch.

So, the head gets real hot, valve guide then pushes out toward keepers, then, the guide won't push back in so easily, push rod bends?

Correct, If you remove the valve and press the guide back into the head without some type of knurling or something to hold it in place it will migrate back out within about 2 hours of pressing it back in.

So what force pushes out the guide?

I suspect it has to do with the compression or other vibration forces, in combination with possible deposits building up on the valve stem and causes extra friction which pushes the guide toward the keeper. The always migrate toward the keeper, never toward the valve head.