Motor almost jumped timing 180degrees

Discussion in 'The Garage' started by domains, Jun 16, 2012.

  1. domains

    domains Been here awhile

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    Hi...XR650L Before dissembling motor I checked compression and got a reading 30... 60... and one time 90... So thought I bent valves. Took it apart and did a leak test with head upside down and it seems fine. I was driving real slow in first gear when it jumped and it almost started with 170degree jump.
    Do i have to take valves off or the leak test is enough? Think my compression tester is messed up, its those rubber tips you push instead of threads. When I push on it maybe the tip closes, works fine on my skidoo but ATV plug's smaller.
    #1
  2. Benesesso

    Benesesso Long timer

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    Did you make sure to hold the throttle WFO during the test? If carbs, must insure any vacuum slide is open too.
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  3. domains

    domains Been here awhile

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    Might take them off to be sure... need to borrow tool
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  4. ADV8

    ADV8 Taumarunui..Darwin..

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    Maybe this mysterious motorcycle has cam shaft decompressors to get those low psi readings.
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  5. domains

    domains Been here awhile

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    My cam chain tensioner was shot from the start making it jump with new chain and sprockets.
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  6. domains

    domains Been here awhile

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    Took them off and they don't look bent while turning them with your fingers but with drill you feel a little wobble.

    Tried my old oem valves to compare (Cheap 80$ valves on ebay)... maybe i'm better off with stock only 12000 miles on them.
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  7. mcma111

    mcma111 Long timer

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    Your working on what? A john deere tractor???
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  8. H96669

    H96669 A proud pragmatist.

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    Now that you edited your original post.:evil Them XR650L have a decompressor.:wink:
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  9. domains

    domains Been here awhile

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    I had The valve cover off when checking compression.

    I noticed the rubber of idler was chewed up but never thought it could make the bike jump timing.... people say they make noises when worn out but i heard nothing, bike was running great.

    It jumped a few times because I noticed power loss... thought maybe it was my imagination :)
    #9
  10. mcma111

    mcma111 Long timer

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    Did you put the bolt back in the cam chain tensioner shaft when you installed the new cam chain???
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  11. domains

    domains Been here awhile

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    mcma111... Yes bolt is/was there.

    Now that I think of it I never heard it made sounds but sometimes when it stalled it made a loud metal to metal sound.

    The shaft of the idler has marks on it aswell.

    I bought a used xr600 off ebay shaft with idler. Next day I saw a new one off ebay 50$ but no shaft. I bet the dealer wants like 150 for it.

    Bine a week still waiting for it :(
    #11
  12. mcma111

    mcma111 Long timer

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    PM sent
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  13. sieg

    sieg Wearing out tires......2 at a time, day after day.

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    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p> </o:p>
    Yes, I also wondered how an engine could jump 180. A tooth or 2 but 180 I don't think so. :huh<o:p></o:p>
    #13