Bad exhaust valve?

Discussion in 'Mechanic and Repair' started by lwcmattlifter, Feb 17, 2005.

  1. lwcmattlifter

    lwcmattlifter LawnSite Senior Member
    from NC
    Posts: 859

    I started to tear down a Kawasaki FB460V that has developed an oil burning problem. The engine is 10 years old with a lot of hours. When I took the head off the exhaust valve was coated with this hard white/gray crusty stuff. What causes this? Did the engine overheat? Spark plug too hot? I will post pics in a few hours. The camera is charging up.
     
  2. Smalltimer1

    Smalltimer1 LawnSite Bronze Member
    Posts: 1,223

    You were running too lean which caused higher cylinder & exhaust temperatures forming those white deposits on the head.
     
  3. lwcmattlifter

    lwcmattlifter LawnSite Senior Member
    from NC
    Posts: 859

    Here are some pics I took this afternoon. As you can see the white junk is all over the exhaust valve. It covers it all the way to the stem. I did not get a picture of the intake valve but it is very worn also.
     
  4. lwcmattlifter

    lwcmattlifter LawnSite Senior Member
    from NC
    Posts: 859

    Could that be caused by too much oil in the combustion chamber?
     
  5. Smalltimer1

    Smalltimer1 LawnSite Bronze Member
    Posts: 1,223

    The way the pic looks it does look like it ran hot for some time.

    The head and the piston are LOADED with carbon, it definitely needs to be decarbonized. Carbon deposits can cause overheating in combination with a lean mixture.

    Blowby can cause carbon to buildup, does your engine smoke or knock?
     
  6. lwcmattlifter

    lwcmattlifter LawnSite Senior Member
    from NC
    Posts: 859

    Yep it smokes and burns oil no knocks though. Any thoughts on the best way to repair this engine? It is only used as a backup and at most will cut 2 small backyards a week. I am not going to replace the engine because I don't use it enough for that. I want it to go for a season or two more until I demote one of my newer mowers to backup. I think I am going to lap the valves and hone the cylinder and install new rings. Whats the best way to get rid of the carbon?
     
  7. mudpie

    mudpie LawnSite Member
    Posts: 45

    I would check the valve guides they are most likely worn. I`ve seen the same thing on briggs engines
     
  8. Travis Followell

    Travis Followell LawnSite Silver Member
    from KY
    Posts: 2,207

    The best way to get rid of the carbon is to scrape it off.
     

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