2 Bent valves in 2 weeks

Discussion in 'Mechanic and Repair' started by Dstosh, Sep 2, 2009.

  1. Dstosh

    Dstosh LawnSite Senior Member
    Posts: 716

    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
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    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 ?
     
  3. bondman35a

    bondman35a LawnSite Member
    Posts: 82

    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.
     
  4. Dstosh

    Dstosh LawnSite Senior Member
    Posts: 716

    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.
     
  5. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    OK guy's,

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

    [​IMG]

    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;


    [​IMG]


    Good Luck
     
  6. Dstosh

    Dstosh LawnSite Senior Member
    Posts: 716

    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!
     
  7. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    Well,

    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 is about the cheapest one I found. Scroll down second-third from the bottom.


    Good Luck
     
  8. Dstosh

    Dstosh LawnSite Senior Member
    Posts: 716

    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?
    [​IMG]
    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.

    [​IMG]


    [​IMG]

    Timing looks good.
    [​IMG]

    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?

    [​IMG]

    Thanks!
     
  9. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    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 ?
     
  10. Dstosh

    Dstosh LawnSite Senior Member
    Posts: 716

    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.
     

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