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Do I need a top end rebiuld?

Discussion in 'Technical' started by JeffM, Jun 8, 2018.

  1. JeffM

    JeffM Active Member

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    Location:
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    My Bike(s):
    Big Dog K-9 2008
    First Name:
    Jeff
    Greetings and salutations fellow Doggers.
    All those who follow this mad Aussie and his affair with his K9 would know i am ok with the spanners and quite happy (sometimes) to try something new ie: AUTO CLUTCH - thankfully i can say i have it working perfectly with NO help from the suppliers, but with grateful thanks to the members on the forum.:old2:

    Next issue, my motor has 40,000 klm (whatever that is in Dog miles) and i am blowing blue smoke at idle, that said i don't appear to be using oil.
    Last weekend my friends and i did 1500 klm over 3 days of quite quick riding (the new 114 HD still can't beat the 117) but i noticed the smoke when stopped.
    I don't seem to be down on power- allowing for general wear and tare from new.
    I have rebuilt several HD motors over my years, live by the addage -"IF IT AINT FUCKED DON"T FIX IT".
    However this is my baby, and i don't want to kill it.
    I thought a hone, re-ring, maybe guilds and a re- lap of the valves would fix this problem.

    Thoughts?
     
    francoblay1, chubs, bigkelk9 and 2 others like this.
  2. bigkelk9

    bigkelk9 Well-Known Member
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    Sounds like u have it all figured out really
     
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  3. pauly

    pauly Active Member

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    Hi Jeff,
    I'm not a mechanic but it would be easy to check few things first before you start
    pulling the motor apart. At idle there is more vacuum in your intake manifold which can
    suck oil mist with crankcase gases into your combustion chamber. I'm assuming that you haven't
    modified breathing arrangement on your motor yet.
    Disconnect your front head breather hose from intake manifold and plug the hose and cap the manifold hose connection.
    Disconnect the rear head breather hose from filter backing plate, cap the hose connection on backing plate and
    leave the hose vent to atmosphere.(might want to extend the hose and run it to ground) Now go for a ride and see if you still have smoke coming out of your exhaust at idle. Also check your oil level after the ride you might over filled it a bit. Restrictive oil filter can cause problems as well. If that helps I would use one of the crankcase ports and put another went hose with check valve there as well.

    Paul.
     
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  4. BWG56

    BWG56 Guru

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    :old2: That was my first thought and you prolly already know this but I would test the compression before I would take anything apart.
    I no mechanic either.
     
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  5. pknowles

    pknowles Getting better by the day...---... GURU
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    Always nice to see members helping other members:oldthumbsup:
     
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  6. Sven

    Sven Well-Known Member

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    Generic blue oil smoke:
    Rings:
    1. Oil is not scrapped off via the scraper ring. The excess oil on the walls burns with the gas.
    2. Excessive ring end gap plus loss of tension at the ring. Compressed air is forced down the wider gaps and cause blow-by.
    3. Detonation can pound so hard over the dome of the piston, it can lock the rings in the grooves and no longer expand out to seal the chamber, or scrape the oil off the wall.
    Cause/Effect... Every time the cylinder fires, the oil loss remains a constant and burns oil in the constant.

    Valve Guides:
    a. Excessive OD to ID clearances cause the oil to be sucked thru the gap via intake stroke.
    b. Guide seal rubber is broken/hard/moved off the guide and floats on the valve stem, then add the intake draw filling the chamber with oil.
    c. Oil flows from head, past the seal's lip, travels down the valve, drops oil onto the piston and is burned upon startup.
    Cause/Effect... Every time the engine lights off in the morning or cold start, it took a few hours to drip oil into the chamber and smoke upon startup and then clears up. When you lift off the throttle and cause the vacuum to pull air from all sources, this vacuum will pull oil from around the OD/ID clearance and leave a bellow of smoke upon throttling back up to speed.

    Conclusion:
    Rings = Constant smoke when running.
    Guides = Smokes upon lift then acceleration, then stops smoking.

    Which is it?
     
  7. Srodden

    Srodden Well-Known Member

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    Good explanation Sven
     
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  8. chubs

    chubs Well-Known Member

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    X 2
     
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  9. pauly

    pauly Active Member

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    Jeff mentioned smoke at idle after riding not at start up after sitting.
    Another thing to check is oil return line for blockage-restrictions.

    Paul.
     
  10. pauly

    pauly Active Member

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    How did you go Jeff?
    Have you looked into it yet?

    Paul.
     
  11. francoblay1

    francoblay1 The Spaniard

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    and here he is, da man is back!!! welcome back Sven! :old2:

    :chopper:
     
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