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Thread: 78 R100/7 Oil Leak

  1. #1
    Mike V. #30064 30064's Avatar
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    78 R100/7 Oil Leak

    Before I go tearing into this thing I wanted to reach out to any of you that have experienced the same problem. This leak(s) makes little sese to me since the only reasonable explanation is oil delivery is getting past both the head gasket and upper head bolt. As you can see; the mating surfaces are dry. Porosity is another possible culprit I suppose, but both heads in the same place? The leak is inconsistent in volumn, sometimes only a visible amount - other times it will wet my boot(s). And the bike seems to using more oil than expected. Compression is high (??160), plugs are clean and not discolored. The bike runs excellent in all circuits and is very strong. Left side head is very similar, a little less visible oil.
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    Mike V. / San Diego
    MOA#30064 / ABC#11027
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA-VBMWMO / http://tinyurl.com/4df7hgs

  2. #2
    --Tony AnnapolisAirhead's Avatar
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    Heads (all 6 bolts) torqued down to 25-26 ft lbs in a criss-cross pattern? Aluminum flexes a lot more than it may seem, so if you torqued them down in a clockwise direction, they could possibly be warped. Possibly, but I doubt it.

    If you are still leaking even with those silicon VC gaskets, perhaps your heads or VC are warped. A good machinist can shave them true. My guess is that the VC and/or heads are slightly warped and at that high compression, oil is being tossed around pretty good, slipping through the VC not the head gasket.

    160 psi is a bit excessive I think, although judging from the black valve covers you must be talking about the '84 R65--I think they have 9.5:1 compression, so I could be off base. Actually, both should be high compression IIRC. Even still high compression should be in the 140-145 psi range I'm pretty sure. Did you check compression with carbs off the bike?

    Funny, I have an '84 R65...but haven't even looked at how many miles are on it...tucked away in storage for now.
    1971 BMW R75/5 | 1975 Moto Guzzi 850T Cafe | 1983 BMW R100RS | 1988 BMW R100GS
    1988 BMW K75 | 1998 BWM R1100RT | 2000 Moto Guzzi Quota 1100ES |2002 Moto Guzzi V11 LeMans

  3. #3
    Mike V. #30064 30064's Avatar
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    Yes, I agree 160 is high. I'm attributing that to carbon build-up. The compression test was done with the carbs off. The heads have been torqued in a criss-cross pattern to 26 ft-lb. I don't believe the oil is coming from the VC gaskets. This only started when I took it to the local boneheads when I had the money and not the time to replace PTS's. My biggest mistake. I took it back and they kindly pulled a stud out of the case and took it upon themselves to install silicone gaskets...not needed in my opinion. I need to do a total top end on it, I'll do that myself this winter.
    Last edited by 30064; 07-09-2010 at 07:53 PM.
    Mike V. / San Diego
    MOA#30064 / ABC#11027
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA-VBMWMO / http://tinyurl.com/4df7hgs

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    Registered User toooldtocare's Avatar
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    This does not make sense, but I had silicone gaskets on a R100RT once and they leaked if I tightened them too much. I finally replaced them with proper BMW gaskets and the leak stopped. I current one on my 78 RS oil pan, and it also leaks. I have a BMW gasket and will install it at the next oil change. The silicone oil pan gasket was on the bike when I got it, so I can only assume that it is also over tight.

  5. #5
    Mike V. #30064 30064's Avatar
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    There is no oil coming from the valve cover gasket on either cylinder. It appears the oil is coming from the 12 o'clock cylinder stud position and puddling around the plug and adjacent fins...but why? There should be no oil delivery there. And if it's getting past the head gasket why isn't it visible at the head-to-cylinder join externally? Guess I just need to go in and have a look at things...maybe double-nut the stud, remove it, clean well and seal the threads with compound after replacing the head gasket and close inspection of existing condition. Appreciate all comments, suggestions and like experiences.

    Maybe I'll try cleaning both sides well and try the talc method.
    Mike V. / San Diego
    MOA#30064 / ABC#11027
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA-VBMWMO / http://tinyurl.com/4df7hgs

  6. #6
    I have seen several bikes leak from the top stud over the years. It seems most prominent in R100s, which have less distance from cylinder edge to stud than R90s, etc. It seems to me that the heads must have a porosity in the area. Replacing head gaskets didn't fix it, so I installed a crush washer under the standard washer. This has so far been successful.

    I wouldn't call 160 PSI excessive. I expect to see at least that and would prefer to see 175 PSI.

  7. #7
    Registered User skiteach's Avatar
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    I'd clean with carb cleaner and then talcum powder, before pulling anything apart. Breather clear and working? Oil overfill?
    '73 R75/5
    Never had a bad day skiing!

  8. #8
    Mike V. #30064 30064's Avatar
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    Quote Originally Posted by lostboy View Post
    ... so I installed a crush washer under the standard washer. This has so far been successful...
    Interesting, tell me more in detail please. Crush washer? Brass, copper, size?
    Mike V. / San Diego
    MOA#30064 / ABC#11027
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA-VBMWMO / http://tinyurl.com/4df7hgs

  9. #9
    --Tony AnnapolisAirhead's Avatar
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    Quote Originally Posted by lostboy View Post
    I wouldn't call 160 PSI excessive. I expect to see at least that and would prefer to see 175 PSI.
    Hmm, ok. I just haven't seen anything north of 148 and Clymer's specs that 145 is 'excellent'. Seems there would be some limit as to what's good and what's too much.

    +1 on the talc powder approach that Skiteach suggests.

    From the pictures, it looks like it is confined to the heads, not the head-to-cylinder joint. Silly question, but are the plugs tight or is it possible the last person to work on them stripped the plug hole threads?

    It could also be that the last shop to work on it re-used the head gaskets, but I still can't see any oil there. Even if the (new) head gasket where installed backwards, I'm not sure it would leak--it will score the pushrods though.

    The silicon gaskets work wonders for me and I'm thinking you have a slightly warped head or valve cover still. Any change that the center valve cover bolt stud is stripped (maybe replaced)? I suppose if that were the case it would be leaking oil on the bottom too and you'd notice that.
    1971 BMW R75/5 | 1975 Moto Guzzi 850T Cafe | 1983 BMW R100RS | 1988 BMW R100GS
    1988 BMW K75 | 1998 BWM R1100RT | 2000 Moto Guzzi Quota 1100ES |2002 Moto Guzzi V11 LeMans

  10. #10
    Registered User skiteach's Avatar
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    Interesting, tell me more in detail please. Crush washer? Brass, copper, size?3

    Copper or Aluminum are the most easily obtained. It may take a friendly counter person at a parts store or dealer. There are lots of these used in fuel injection systems. A shop that specializes in foreign cars might be another source. Should not be too hard to find a 10 mm crush ring.
    '73 R75/5
    Never had a bad day skiing!

  11. #11
    Yarddog
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    Quote Originally Posted by skiteach View Post
    Interesting, tell me more in detail please. Crush washer? Brass, copper, size?3

    Copper or Aluminum are the most easily obtained. It may take a friendly counter person at a parts store or dealer. There are lots of these used in fuel injection systems. A shop that specializes in foreign cars might be another source. Should not be too hard to find a 10 mm crush ring.
    Also a Dorman oil drain plug assortment might contain a copper crush washer...

  12. #12
    Mike V. #30064 30064's Avatar
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    I'm trying to understand how a crush washer against the head surface and around the cylinder stud could stop the flow of oil "if" it is in fact getting through that area and past the stud threads. And, how the crush washer may affect head torque. If this is so...the oil must be getting past the head gasket, right? If not, it must be getting through the casing material by ways of porosity. But in the same place in both heads? What are the chances of that? I think I'm shooting at windmills until I have a look inside and can closely inspect the gasket material and installation. Not to mention other things.

    Keep 'em coming guys, appreciate the replies. I'll get to the bottom of this sooner or later. Most likely later...I'm planning a x-country tour next month.
    Mike V. / San Diego
    MOA#30064 / ABC#11027
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA-VBMWMO / http://tinyurl.com/4df7hgs

  13. #13
    Registered User skiteach's Avatar
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    The head gasket seals the compression area of the combustion chamber. The balance of the gasket supports this ring and may seal some of the stud holes. It has been quite a while since I saw Airhead gaskets. As I remember the oil reaches the head thru the push rods and not thru a pressurized passage, as is the norm for most other types of engines. There is not any provision applied to the gasket (silicon beads applied) to seal the stud holes. This might allow oil to migrate under and around the head nuts and washers, following the stud to the areas you see. By inserting a crush washer under the washer it would provide sealing in that area.
    '73 R75/5
    Never had a bad day skiing!

  14. #14
    Mike V. #30064 30064's Avatar
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    Teach,

    The oil is delivered under pressure along the upper two cylinder studs directly to the valve assemblies and is returned to the crankcase through the pushrod tube seals.
    Attached Images Attached Images
    Mike V. / San Diego
    MOA#30064 / ABC#11027
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA-VBMWMO / http://tinyurl.com/4df7hgs

  15. #15
    Registered User skiteach's Avatar
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    Told you it'd been a long time! 30 yrs I'm thinking. Ok, as Lostboy said, that top center stud is the area that it's leaking and there's no sealing bead there, nor at the bottom studs either. Are you seeing any leaks at bottom? If that's your head gasket, it looks pretty good, or new. If it were mine and it was down that far , I'd run a small bead of Halomar around the studs that are not already sealed. The crush washer would not hurt either and can be done without head removal. I have seen silicon sealers used in place of crush washer- but it should be VERY sparingly used.
    '73 R75/5
    Never had a bad day skiing!

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