Leaking Left cylinder

Discussion in 'Airheads' started by globalt38, Apr 16, 2018.

  1. globalt38

    globalt38 "A Fist Full of Throttle"

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    Need thoughts from the collective wisdom...
    First things first - 1994 R100 GSPD, ~ 45k miles on it, original top end (no piston, ring, cylinder work done to date).

    Returning from a ~500 mile round trip outing a while ago noticed a lot of oil from the left side. Enough that it was making my shifter lever slick and the toe of my boot slick enough I had to be careful putting my foot down or it would slip out. When I got home, took a look and there was oil on the carb, shifter, and top/bottom of the cylinder.

    Top of left carb
    [​IMG]

    Cylinder Intake
    [​IMG]

    Carb Air Intake
    [​IMG]

    Cylinder bottom (with filthy pushrod tubes)
    [​IMG]

    [​IMG]

    So I cleaned things up some and, prior to my next ride little while later I dusted with talcum
    Again, lots of oil on carb, boot, and shifter.
    When I got back - could tell that, while might be a slight leakage at the pushrods - it was not the cause of all the oil. Looks to be from the head gasket area which is being misted/slung onto the carbs, shifter, and my boot toe. As you'll see from the pics - the only other thing would be the cylinder intake from the carb? (would a lot of oil leakage from that be possible?).

    Cylinder top after second ride
    [​IMG]
    [​IMG]

    Cylinder intake
    [​IMG]

    [​IMG]

    Here's a shot of the bottom after being parked little bit (sorry bit blurry)
    [​IMG]

    And in anticipation (and because I got them for Christmas) - I did a compression test and leakdown test. Carbs were removed and I ran the bike to get the temp up but it probably cooled little while I got the carbs off.

    Compression test of right (non-leaking) cylinder
    [​IMG]

    Compression of left (leaking cylinder).
    [​IMG]
    So looks to be about ~10 psi less on the left.

    Leak down test on the left cylinder
    [​IMG]

    So looks to be about 4psi (4%) loss. Felt around and felt a little air from the exhaust valve and when I opened the oil filler/dipstick could "hear" air in the sump but didn't feel any coming out the filler.

    So - thoughts?
    Is the oil leak coming from the head gasket or could it be a bad seal at the cylinder intake?
    Is the compression and leak down test bad enough to indicate bad rings or?

    Thanks for all the help I know I'm sure to get.

    Advance warning - because I know folks like instant gratification - my ability to really get to work on the bike is often sporadic depending on many variables and the bike is in a shed/shop up the hill that is my back yard (no garage) that requires me to run an extension cord for light/power so it's not a quick hop out to the garage to check/confirm something. :1drink
    #1
  2. IdahoAirhead

    IdahoAirhead Been here awhile

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    I'd bet it's a head gasket.
    There is no oil in the intake path anywhere to leak out the carb rubber.
    To confirm that for yourself, just take off the clamp that holds the carb into the rubber on the head, pull the carb off and look inside. Not likely to have any oil inside at all.
    As mis-installed as that clamp is, you may not even have to loosen it to pop the carb off . . . .
    #2
  3. Rucksta

    Rucksta SS Blowhard

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    Install the hose clamps on the inlet tubes with the screw to the top.
    #3
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  4. ritetwist

    ritetwist Been here awhile

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    1995 R100 GSPD here. 184,000 kms. (114,000 miles.) Never been apart since I bought it with 103,000 kms.
    4/5 years ago I had the same problem you describe.
    Turns out that the bolt through the airbox into the trans. had backed out. Oil was splashing up into the airbox and coming down the air tube.
    It made a real mess, the trans was down quite a bit on oil. Smell the difference,?
    #4
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  5. Steve W.

    Steve W. Boxer Pilot

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    Check the torque on the head nuts, you might ( I hope NOT) find a pulled stud.
    Cheers
    #5
  6. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    +2 on that.

    also you will get a little oil from the engine breather which is routed through the carbs to be burned off. My G/S had a little oil dripping from the left carb intake (at the inlet side of the carb...from air cleaner to carb boot) this quit when the breather was rerouted directly to the atmosphere....shhhhh do tell the EPA
    #6
  7. cycleman2

    cycleman2 Long timer

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    Yes check the carb inlets and the air box. If the PCV valve isn't working properly it will put excess oil into the intakes, although that is usually on the right side, but it can go both ways. You may also have been overfilling the crankcase with oil and the pressure in the block will push it out. With the amount of oil around the left intake runner, I would suspect something in relation to the air intake. Also could be the bolt in the bottom of the air box that attaches it to the top of the transmission that could be allowing oil up into the air stream. ( Somebody else mentioned that one ).

    Compression and leak down look OK to me, anything over 120 is fine. What colours are the spark plugs, difference between left and right side. Excess oil can and will collect in the well area just inside the intake side of the head. Again remove the carbs and have a look around.
    #7
  8. bmwrench

    bmwrench Long timer

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    How much oil does the engine consume?
    #8
  9. hardwaregrrl

    hardwaregrrl ignore list

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    Mark, I'm pretty good at pulling shit apart if you want to leave it here. Maybe it's just time for head gaskets and pushrod refresh.
    #9
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  10. Solo Lobo

    Solo Lobo airhead or nothing

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    Pull off the carbs elbows and check the insides, if they are oily (like the outide) I would say it is very unlikely the source is the head gaskets... how would the oil get inside the intake elbows?

    My guess is that it is blow-by given what I am seeing that is pushing the oil out the stock breather system into the elbows. Also pull the airbox lid and air filter and look for evidence of oil in the bottom half of the airbox as well. Is there oil leaking out the clambshell/gooseneck onto the back of the transmission?

    My G/S pushes quite a oil through the breather, even though the heads are recently rebuilt and the compression is 160+
    #10
  11. globalt38

    globalt38 "A Fist Full of Throttle"

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    Thanks for all the speedy replies! Nothing less than I expected!

    A :doh moment here - I did peek inside through the inlet when I pulled the carbs prior to the compression test and did see now that I think back - pretty dry in there...

    Forgot to mention I did pull the airbox and filter to check and make sure - just a residual oil in bottom of airbox - nothing unusual. Will check to make sure but pretty sure the bolt to the trans hadn't backed out and also sure the oil isn't trans but will check the bolt to be sure. Also it was a lot of oil and more than I think would come through the carbs (but could be wrong there).

    It was losing a bit on the rides bmwrench - did check it frequently and had to put more in couple times - should have kept track but didn't :bluduh

    So it sounds like bad gasket and the compression/leak down doesn't indicate bad rings as the cause?
    I'll double check the airbox and carb inlets and intake side of the head to be sure I wasn't missing anything but again I think the oil on the carbs was from blow back off the head.

    Jenna - generous as always! - if it's just the gasket I can do that myself and like I said, very minor weep possibly at the pushrod seals so may wait on those - will see. I'll definitely keep it in mind though! :wave
    #11
  12. Pokie

    Pokie Just plain Pokie.

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    Judging by your mileage, this might be a good time to do some head work anyway. When the heads are off, check the mating surfaces for flatness. Likely the one head is starting to warp a bit, allowing a leak to start.
    #12
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  13. globalt38

    globalt38 "A Fist Full of Throttle"

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    You are probably right Pokie...

    Checked the both the carb and head intakes again this morning to be sure - little bit of residue in the elbows but nothing unusual. Cylinder intake was dry - felt around inside to be sure.

    Will see about pulling the head by this weekend and will let you all know what is there - will take plenty of photos of it.

    Thanks again for all the input!
    #13
  14. globalt38

    globalt38 "A Fist Full of Throttle"

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    Alrighty

    Pulled the "incontinent" left head on Saturday.
    First off - someone asked about how the plugs looked so took some pics of those as well.
    Right plug (non-leaking side)
    [​IMG]

    Left Plug (leaking side)
    [​IMG]

    Checked the valve clearance first and both were way too tight - couldn't fit a .1mm gauge between either the intake or exhaust! :bluduh

    Also re-torqued the head studs to check to see if any were pulled. All torqued just fine at 25 foot lbs. When I broke them free before retorquing them, however, the bottom left (front) stud was not tight/torqued at all - possible cause of the head leak?
    [​IMG]

    Minor irritation when pulling the head and discovered I'd have to loosen and move the head guard first. :dirtdog
    [​IMG]

    Cylinder and Piston head with gasket still on
    [​IMG]
    [​IMG]
    [​IMG]
    Looks as if the leak was exhaust/front side of the head/cylinder? (loose bottom front head stud nut mentioned above?)

    Gasket removed
    [​IMG]

    [​IMG]

    Head and Valves
    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Told ya I'd take lots of pics! :-)

    So - what are the thoughts and suggestions. If possible distinguish between the "do now before riding again"; the "Good idea to do soon if not now"; and "probably want to think about doing this in the future before putting too many more miles on it" recommendations. :deal

    Thanks in advance for the help! :beer
    #14
  15. Geezerrv

    Geezerrv Been here awhile

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    My question would be why 1 loose stud? Are the block threads failing?
    #15
  16. globalt38

    globalt38 "A Fist Full of Throttle"

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    Good question - but they did not appear to be when I re-torqued them/it. It was the last one I "loosened" before re-torquing - would that have made a difference?
    #16
  17. bmwrench

    bmwrench Long timer

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    Pull the cylinder, then remove the stud in question, and examine the threads.
    #17
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  18. Geezerrv

    Geezerrv Been here awhile

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    Others with more experience on Airheads to answer that. I would think it had to be loose even before you’d torqued the other 3. I may be wrong but I have never seen a head move enough to make a loose nut.
    #18
  19. globalt38

    globalt38 "A Fist Full of Throttle"

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    Would the way to remove the stud be to put 2 nuts on the stud and use the inner to unscrew the stud?
    #19
  20. bmwrench

    bmwrench Long timer

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    Yep.
    #20
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