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Thread: mystery vent...

  1. #1
    zsnider
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    mystery vent...

    So, there is a small curved pipe on the front left bottom corner of the engine on my R50. The Clymer manual doesn't say a word about this vent, I have some ideas about what it is and what it is doing but I am looking for a more detailed description.

    Also, after replacing both head gaskets the bike is running a bit rough. it is difficult to start, it feels a little sluggish at low RPM, and is slow to pick up. The exhaust is more white than normal, and the Mystery vent from in my first question is blowing out a bunch of white / gray exhaust.

    Is this a carb tuning problem or is there something else i am missing?

  2. #2
    Administrator 20774's Avatar
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    That curved pipe is the outlet for the crankcase breather system. If it's pushing out white smoke, it sounds like the system has been improperly installed or something has broken. IIRC, the system was improved over the years and can be retrofitted. I had my R69S overhauled and do not have any noticeable smoke out the pipe but did before I worked on the bike. It could also be that the something is wrong with the top end and there's excess crankcase pressure and the air has to go somewhere. Since you just replaced the head gasket, that's where I'd start. Try a compression test, leakdown test, etc. Check valves, timing.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Little Egypt Airheads
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    Quote Originally Posted by zsnider View Post
    So, there is a small curved pipe on the front left bottom corner of the engine on my R50. The Clymer manual doesn't say a word about this vent, I have some ideas about what it is and what it is doing but I am looking for a more detailed description.

    Also, after replacing both head gaskets the bike is running a bit rough. it is difficult to start, it feels a little sluggish at low RPM, and is slow to pick up. The exhaust is more white than normal, and the Mystery vent from in my first question is blowing out a bunch of white / gray exhaust.

    Is this a carb tuning problem or is there something else i am missing?
    It's possible you've installed the head gasket(s) incorrectly. The oil feeding the rockers drains back into the case through a hole in the head connected to a small pipe (I think) that allows drainage back into the crankcase. I'm not sure if the gasket has the hole on both sides making incorrect installation impossible. Did you use any gasket sealer on the head gaskets? They are supposed to be installed dry and any sealer might have plugged up the hole, too. Your symptoms sound as if oil is trapped in the rocker cover and being forced into the combustion chamber by crankcase pressure thus causing smoking exhaust. Blowby past the rings would cause this smoke to be present in the crankcase and would exit through the breather tube you noticed. All this would mess up performance, too. Hope this helps.
    Little Egypt Airheads,
    '66 R50/2
    '76 R75/6
    '80 R100RT

  4. #4
    Administrator 20774's Avatar
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    This is the way my R69S head gasket went on....dry as indicated...

    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
    zsnider
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    I installed the gasket dry and there is one hole in the gasket for the oil drain that was clear when I installed it. If it is clogged there would be a bunch of oil under the valve cover when I pull it off right?

    What is a leakdown test?

    what causes the timing to change? is it possible that I changed it accidentally while the heads were off?

    thanks for your insight.

    ~Z

  6. #6
    Cam Killer marchyman's Avatar
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    Quote Originally Posted by zsnider View Post
    What is a leakdown test?
    A leakdown test is sometimes done after a compression test to help isolate where compression is being lost. You pump air into into the combustion chamber at TDC of the compression stroke and measure how much is being lost. You can also sometimes feel or hear where it is being lost, e.g. out the exhaust (bad exhaust valve) or out the carburetor (bad intake valve). If neither of those, but you are still losing pressure you can bet it is the rings.

    You need a leakdown tester and source of air.

    // marc

  7. #7
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    If this is the same bike that posted all the earlier valve clearance problems and overtorque fiasco then the carbs were tuned before your head gasket replacement for a bike with at least one valve that was not closing all the way - certainly you will have to do a complete carb adjust after having fixed the valve clearance problem and installing new head gaskets.

    Also timing may be suspect - sluggish at low rpm might indicate a spark advance mechanism that is not working or sticking and the blowby and hard starting might be caused by timing being way off.

    There are so many variables involved with your problems and you have so little understanding of the engine as evidenced by your not knowing what the breather pipe is for - you really need to be working with a person with much more experience looking over your shoulder and advising you before you absolutely destroy the thing.

    If this sounds nasty it certainly is not intended to be so - but I know from my own personal experience as a stubborn young man many years ago how much damage one can do and how quickly understanding is gained when one can be taught by one who actually knows.

  8. #8
    zsnider
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    Quote Originally Posted by 44006 View Post
    If this is the same bike that posted all the earlier valve clearance problems and overtorque fiasco then the carbs were tuned before your head gasket replacement for a bike with at least one valve that was not closing all the way - certainly you will have to do a complete carb adjust after having fixed the valve clearance problem and installing new head gaskets.

    Also timing may be suspect - sluggish at low rpm might indicate a spark advance mechanism that is not working or sticking and the blowby and hard starting might be caused by timing being way off.

    There are so many variables involved with your problems and you have so little understanding of the engine as evidenced by your not knowing what the breather pipe is for - you really need to be working with a person with much more experience looking over your shoulder and advising you before you absolutely destroy the thing.

    If this sounds nasty it certainly is not intended to be so - but I know from my own personal experience as a stubborn young man many years ago how much damage one can do and how quickly understanding is gained when one can be taught by one who actually knows.
    that is why I am here on the tech forum. 44006 thanks for the encouragement.
    ~Z

  9. #9
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    I noticed in the 2007 anonymous book that there is an entry by a person in your same city showing the vtg code among others - if this is not your entry perhaps you might give this person a call and maybe you could get some in person guidance from someone who knows the sound and feel of one of these bikes.

  10. #10
    Administrator 20774's Avatar
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    Anton has a shop in Charlottesville, VA. His website is http://www.largiader.com/shop/. He specifically states '70s on but I'm sure he's also plugged into the local BMW community.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  11. #11
    zsnider
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    Anton Has been very helpful through my mechanical adventures with this bike.
    ~Z

  12. #12
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    Your earlier posts indicated that one head gasket was leaking before you started all this.
    If smoke (not just air with slight oil mist or condensation vapor) comes out the breather pipe it indicates a probable similar leak even though new gasket installed.

    Can you confirm that groove in head into which cylinder sleeve protrusion fits is deep enough to allow head gasket to be compressed and not have condition where cylinder sleeve bottoms out in head groove not deep enough or caked up with carbon?

    Did you confirm that head surface was actually flat by rubbing on piece of glass or similar?

    As far as hard starting and sluggish slow speed behavior confirm you do not have same problem I sometimes have with neglected 1967 R50/2 - one carb slide sometimes sticks in its bore and does not fully drop to bottom on throttle off - need to move the rubber cable protectors out of the way at the cable/carb junction to confirm one cable not hanging up by checking cable slack at throttle off is same both sides - you cannot feel this in the grip. If one slide sticks very hard to start and runs on one cyl till throttle open far enough to actually start lifting both slides.

  13. #13
    Rally Rat
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    A possibility that nobody has mentioned above: check the crankcase breather vent at the top of the case. There is a simple valve in there which is supposed to contain and neutralize crankcase pressure from the cylinders' simultaneous movement.

    But white smoke out that breather would indicate burning oil: somehow oil is getting into the combustion chamber and then into the crankcase cavity......?

  14. #14
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    Quote Originally Posted by rpeckham136133 View Post
    A possibility that nobody has mentioned above: check the crankcase breather vent at the top of the case. There is a simple valve in there which is supposed to contain and neutralize crankcase pressure from the cylinders' simultaneous movement.
    I think the reason no one mentioned a breather valve at the top of the case is because this is an R50/2 (I assume the /2 since this is a vintage board) and it doesn't have anything on the top the engine. It does, however, have one that fits to the front of the engine, and hence routes the air to the "mystery vent" at the lower front of the engine.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  15. #15
    zsnider
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    Quote Originally Posted by 44006 View Post
    Your earlier posts indicated that one head gasket was leaking before you started all this.
    If smoke (not just air with slight oil mist or condensation vapor) comes out the breather pipe it indicates a probable similar leak even though new gasket installed.

    Can you confirm that groove in head into which cylinder sleeve protrusion fits is deep enough to allow head gasket to be compressed and not have condition where cylinder sleeve bottoms out in head groove not deep enough or caked up with carbon?

    Did you confirm that head surface was actually flat by rubbing on piece of glass or similar?

    As far as hard starting and sluggish slow speed behavior confirm you do not have same problem I sometimes have with neglected 1967 R50/2 - one carb slide sometimes sticks in its bore and does not fully drop to bottom on throttle off - need to move the rubber cable protectors out of the way at the cable/carb junction to confirm one cable not hanging up by checking cable slack at throttle off is same both sides - you cannot feel this in the grip. If one slide sticks very hard to start and runs on one cyl till throttle open far enough to actually start lifting both slides.
    I checked both the cylinder sleeve depth and the "flatness" of the head surface. both are OK. I will check that carb slide.

    My next course of action will be to reset the timing. Does anyone have any helpful tips and or specific things to look for while doing this? any and all help would be appreciated.

    thanks.

    ~Z

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