Tool

Discussion in 'Mechanic and Repair' started by andy35321, Jul 4, 2012.

  1. Patriot Services

    Patriot Services LawnSite Fanatic
    Posts: 12,446

    Personal theory on testing at past TDC. If there is any ridge at the cylinder top it can interfere with the ring to cylinder contact. I have an OTC model that's probably 20 years old. This is important info. Guys throw tons of parts at a problem when only to find out its lacking enough compression to even start.

    But that's what Motor Honey is made for. Right?
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  2. andy35321

    andy35321 LawnSite Member
    from georgia
    Posts: 189

    So patriot where do you go 1/4 past tdc. Thanks for all the replies.
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  3. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    If there is a ridge at the top of the bore...there is probably another just like it at the bottom of the bore..The ridge is a result of worn rings and/or a "Piston Slappin' ":waving:..As the purpose of the leakdown test is to best figure the internal condition of the valves and rings without taking it apart..The more info you can get...The better...
     
  4. BigFish

    BigFish LawnSite Silver Member
    Posts: 2,915

    Hey, that works! I've used the ol' blowgun trick many times! Either way, ya gotta get past the point where the ACR is holding one of the valves open. Usually you have to bring the piston PAST top dead center by about a quarter inch or so. On OHV units, you can check the rockers for play and go with that.
     
  5. BigFish

    BigFish LawnSite Silver Member
    Posts: 2,915

    Yes, both valves have to be closed.
     
  6. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Just loosen the rocker arms...pop them off the pushrods...and put the air to the cylinders...
    Keep it simple...
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  7. Patriot Services

    Patriot Services LawnSite Fanatic
    Posts: 12,446

    Your assuming the person loosening the valves has the skills to readjust them. But that will be another thread.
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  8. andy35321

    andy35321 LawnSite Member
    from georgia
    Posts: 189

    I like to keep it simple. Most times when I adjust valves I just open one then adjust the other. And do the same for the other.
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  9. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Another thread indeed....
    Exposing the people with leakdown testers that don't know how to adjust valves..
    By the time I have to perform a leakdown test....the head is usually coming off anyway...for one reason or another...
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  10. Bashby

    Bashby LawnSite Senior Member
    Posts: 446

    I'm used to working on cars, no compression release. So the acr holds the exhaust valve open at tdc on compression stroke?
     

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