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Loose valve rocker arms

in General Tech Discussion 10 years ago
While doing a condition inspection on my Rotax 912 ULS Powered RV-12, I noticed an oil leak at the bottom of the #3 valve cover. On removing the cover I discovered both the intake and exhaust rocker arms weren't firm. I then removed all valve covers and found the same condition on the exhaust rocker arm for cylinder #4. The rest were firm.

I'm assuming the valves are self adjusting (Hydraulic lifters). So, what's the solution for returning the rockers to a firm condition?

Walt Shipley

  • Re: Loose valve rocker arms

    by » 10 years ago

    Hi Walt,

    So long as the oil hasn't been drained out of the system that would affect the lifters then this may be normal.
    We would need to ask what happens when you rotate the prop at least 180 degrees from where those particular ones were loose? Are they still loose or did they firm up?
    If you haven't drained the oil out of the system then run the engine for 1-2 minutes and check them again.

    If the oil was drained out and did affect the lifters then an oil purge would need to be done before running it again.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: Guilherme Tomazini
      
    Report

  • Re: Loose valve rocker arms

    by » 10 years ago

    Roger, thanks for the reply. I turned the prop and the lifters that were loose did tighten back up. However, the three lifters in question get much looser than the rest of the lifters. I'm probably going to have to do a purge and then attempt to push the lifters down with the plastic or wooden handle of a hammer as shown in the oil purge video.

    Thanks again. Walt
      
    Report

  • Re: Loose valve rocker arms

    by » 10 years ago

    Roger, since my last post on the loose rocker arms, I did an oil system purge and ran the engine until the oil reached 122 degrees. I then rechecked the rocker arms that had been loose and they were nice and firm. However, once the engine cooled back down, those rocker arms again loosened up.

    I discussed this situation with tech support at Lockwood and they said they had never heard of a situation where the rockers are firm when hot, but not when cold. Right now I'm on the fence about which way to go. On the surface, it would seem if the rockers are all firm when the engine is running, I shouldn't have anything to worry about. But, maybe not. What is your input?

    Thanks, Walt

    PS To make matters worse, today I cross threaded the top #4 spark plug!! Hopefully Rotax will condone a heli lock if I can find one in the right size. ARGH! This has turned into the Condtion
    inspection from Hell.
      
    Report

  • Re: Loose valve rocker arms

    by » 10 years ago

    I would bet your rocker arms are okay. Just get a 12mm spark plug thread chaser. Spark plug thread chasers are not sharp edged like a standard tap and don't cut new threads. The plug tap has more rounded edges to reform the threads. Do this first before doing anything else.

    http://www.matcotools.com/catalog/product/SPT100/12MM-SPARK-PLUG-HOLE-CHASER/


    http://www.amazon.com/Jack-Sealey-Spark-Thread-Chaser/dp/B000R9Y5JG/ref=sr_1_1?ie=UTF8&qid=undefined&sr=8-1&keywords=12mm+spark+plug+thread+chaser

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Loose valve rocker arms

    by » 10 years ago

    I run this 1/4-1/2 inch on every plug hole when I change the plugs.
    Thank you said by: Walt Shipley
      
    Report
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