View Full Version : 2 Bent valves in 2 weeks

09-02-2009, 11:09 PM
Got a bent intake valve on one side of the motor about two weeks ago. Took me some time to fix it, but I did. Motor ran really well for about three days. Today the intake valve bent on the other cylinder. Almost identical to the way the other valve bent before.

Why is this happening? Can the timing be off? If so how did it get off and how do I adjust/check the timing.

Kawasaki 25hp f721v

09-03-2009, 12:10 AM
It wouldn't run very well with the cam timing off, What spec are you adjusting the valves at ?

Did/do you see a contact area on the piston ?

09-03-2009, 01:02 AM
Yea there is contact area on the piston from where it hit the valve, on both pistons. Just knocked the soot off the piston, nothing really major. The valves were adjusted to between .003-.005. Dstosh is my brother, need to get this sorted out.

09-03-2009, 08:58 PM
Yea, there is some contact area, but there is no gouges on the actual piston, you can't feel any. The valves are being adjusted like my brother said .003-.005cold at tdc I tried to do them at around .003 though.

09-03-2009, 10:06 PM
OK guy's,

There could be a issue with the automatic compression release on the camshaft;


It could be randomly hanging up and caused the valves to float into the pistons under full throttle rpm's ?

In any event I believe the valves opened too far and hit the pistons over the pistons moving too far and hitting the valves, If the pistons went too far you would hear the rods rattling/knocking.

It looks like maybe a tear-down inspection is in order to check the cam timing and compression release;


Good Luck

09-03-2009, 10:13 PM
Rob, where are you gathering these images from? What would be a good refrence book for working on these 25hp kawi's? Thanks for your help!

09-04-2009, 12:17 AM

I work for a Kawi (among others) dealership and I have two computers and two photo host sites jam packed with repair details/images I've collected over the years.

Your best bet is investing in a factory service manual, THIS (http://www.psep.biz/store/kawasaki_small_engine_service_manuals.htm) is about the cheapest one I found. Scroll down second-third from the bottom.

Good Luck

09-05-2009, 08:00 PM
Rob, Got it torn down today. There was nothing out of the ordinary. Or so I think.

There was a washer that fell out. Not sure where that goes?
Thats a 12mm Socket next to it for ref.

The automatic compression release is where? Is it the thing with the 5 or 6 balls and the floating plate? There is some type of linkage that hooks up to the outside of the motor and it looks like it controls how that thing with the balls floats.



Timing looks good.

The screw/spring that keeps the rpms in check was missing. It must have vibrated out. 92009a and 92145 In the picture. Could that be the reason it is hanging up?



09-05-2009, 09:38 PM
Taken in your order,

The washer goes on the end of the camshaft, It keeps that snap ring you see from gouging up the pan.

The camshaft picture I posted IS the cam for your engine, My picture is shown from the back side therefore the compression release is on the back side of yours pictured. Lay the engine down with the pto end of the crank facing up, With the timing makes aligned as you have them you should be able to lift the cam from the block. Be VERY careful that the valve tappets do not fall out, You do not want them to get mixed up.

Once the cam is out look at the compression release lever, Check for any burrs or wear. Also see that the return spring is intact and the spring pulls the lever back in smoothly.

The plate on the front of the cam with the balls is the governor assembly.....

Just a detail to keep in mind when re-assembling;

In the third pic of the pan, Make sure the governor arm stays in the same position it is in the pic with the black plate with two fingers as is when flipping the pan for installation (hold it with hand).

Also, When sliding the pan back on make sure the oil pump gear meshes properly with the crank gear, You may need to fish a small screwdriver between the block and pan to rotate the pump gear a little to get it meshed.

The screw and spring is nothing but the idle speed adjuster, Were you having low/no idle speed problems before ?

09-05-2009, 10:37 PM
Trying to adjust the Idle when we had low/no power problems. Further diagnosis-bent valves.

I give pulling the cam a shot.

Some one had suggested to me that the valve guides were worn. When you put the corresponding valve in the head that the valve was bent in, there is no play.

Is worn valve guides a possibility?

Thanks for your help.

09-06-2009, 12:30 PM
I went throught this with a 25hp kawasaki. It was on a Deere. The problem they were having was with the valve guides were coming loose in the heads, and the push rods and valves were getting bent.

There were alot of unit i know that had this problem. kawasaki recommends your replace the heads, gaskets, etc. It corrected the problem with these units along with the one i repaired.

if you want more info let me know. I have a bulletin on this.

09-06-2009, 01:21 PM
Leeker-Could you post up the bulletin on this? Thanks

I would hate to have to buy new heads for it. Could I have someone put new guides in there?

I havent had any push rods bend-could be the luck of the draw?

09-06-2009, 03:38 PM
The way it sounds this is your unit or your brothers, so you can try this. I did notice that the new heads(looked to me like) the guides were pinged in the head when I recieved them.

Like you would do when you reinstall an old valve seat in a head that has come loose. (You know what i mean?)

set the valve guides to the correct distance if they have moved and ping the guides on both sides of the head. In the valve chamber next to the guide and on the top side. This will help hold the guides in place.

Kawaskai states this is from the engine having to much grass and debris in the engine compartment and it overheats. Maybe, but the owner of the mower I repaired is a customer of mine and it is always blow out the engine and is very well taken care of.

If you install new heads and valves you are supposed to ream the guides with a 6mm reamer before installing the valves. If you keep your old heads and install new valves I think I would do this anyway.

An easier way to see if the guides have moved is to put air to the cylinder to keep the valves up and take the springs off. this way you can see the guides and valve seals. I could see that the seals were getting crushed on this one.

****I would only recommond doing the valve guide repair like i suggested if it is your own. the cost of the heads, gaskets,(head-intake) seals, push rods, were about $450.00 from deere. heads were $200.00 a piece.****

let me know how you come out!!!!!!!!!!!!!!

09-06-2009, 06:45 PM
Not sure on how exactly to ping the vave guides. Can you explain this process? How should I do it. I have new valves for both. (intake only).


09-06-2009, 07:24 PM
Pinging would be with a hammer and a small pionted punch. You take the hammer and hit the punch against the aluminum to push it against the steel guide. You do this in a back on fourth motion. (NOT ONE SIDE THEN THE OTHER)

You want to be about 1/16 of a inch away from the guide when you do this to cause the aluminum to press against the guide. Then go back and fourth like in a pattern of 12 oclock then 6 oclock, then 10 and 4 then 2and 8 and so on.

Look up a website "How to install a loose valve seat" The pic shows how to ping. This is showing you on a seat not a guide. But the pinging is the same. You will see how you build the aluminum up around the guide. I found a pic, but i dont know how to upload it.

I know restrorob knows what i mean maybe he could find you a pic to upload.


09-06-2009, 07:28 PM
Alright I'll give it a shot. Thanks for the help.

09-06-2009, 07:40 PM
I know restrorob knows what i mean maybe he could find you a pic to upload.

Yes I do leeker, This is the only pic I found. So use a pointed punch slightly away as leeker mentioned.



Can you post this service bulletin number and where you found it ?

The first thing I did was check for bulletins and none pertained to guides.....

09-07-2009, 10:00 AM
what i actually have is a Dtac solution from deere. I worked for them for quite awhile and always stop for coffee everyday. We have a good relationship on working together they allow me to look at these.

But i would be more then glad to fax or send you a copy of this. Not to sure how to upload.

09-07-2009, 04:50 PM
One question.... I thought most small engines were non-interference, or are they? So to hit the piston, a valve must be sticking out along with it's seat. Valve lash opens up, operator re-adjusts thus providing the extra path to strike the piston, is this possible?

09-07-2009, 11:10 PM
sorry, if i dont understand your question right, but in this thread when referring to the seat i was referring to pinging in a seat. Not that this engine had a loose seat.

This engine they have has a problem with the valve guides, valves, head gaskets, etc.

I believe what has happened in this engine is the valve has stuck in the guide after it gets hot and then the valve was struck by the pistion when it was stuck down(I believe). I do know that this has been a problem.

dont know how much the valve was bent, but it wouldn't take much. That is about all it can be if the timing marks are lined up and the engine runs on the other cylinder fine. Sounds like the other cylinder though he had apart two weeks prior.


10-22-2011, 12:53 AM
I went throught this with a 25hp kawasaki. It was on a Deere. The problem they were having was with the valve guides were coming loose in the heads, and the push rods and valves were getting bent.

There were alot of unit i know that had this problem. kawasaki recommends your replace the heads, gaskets, etc. It corrected the problem with these units along with the one i repaired.

if you want more info let me know. I have a bulletin on this.

Hey Leeker i think im having this problem with my 757. Can you send me this bulletin? thanks for your help!