Pushrod seals replacement

Discussion in 'Airheads' started by bikecat, Nov 3, 2010.

  1. bikecat

    bikecat Long timer

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    No problem; we're all learning here, and I am grateful for the knowledge and information imparted.

    Things took an interesting turn when I worked on the bike. I removed the valves with the help of a valve-spring compression tool:

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    The valves were not wearing evenly; any idea what would cause this?

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    Started cleaning the cylinders ...

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    I've learnt that it is important not to mix up the left / right sides; critical to label them properly. Take things slowly is important; almost like a zen approach. Next thing I did was to clean the pistons ......... that's where it got interesting .....

    Cheers
    #21
  2. Jasper ST4

    Jasper ST4 Guest

    Is it possible to mix them up? The spark plug hole would be on the wrong side.
    #22
  3. fishkens

    fishkens Long timer

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    Not likely that you'd get the heads confused but it's probably not a bad idea to mark the cylinders, etc. to keep parts together.
    #23
  4. wirewrkr

    wirewrkr the thread-killer

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    It's actually impossible to mix them up.
    The intakes and exhaust spigots are not concentric, they would point off in odd directions.
    #24
  5. fishkens

    fishkens Long timer

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    Exactly why it's not likely.:D That and the fact that the push rod holes would've gone all /2 on you ifn ya tried to point the intake/exhust in the right direction.
    #25
  6. kbasa

    kbasa Roubaix! Super Moderator

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    It looks to me like that one valve wasn't closing. You can see carbon all over the face of the valve seat, which should never, ever be there. I assume you were having compression issues on that cylinder?

    Your real task here is to figure out what's up with that valve. Was it left too tight during an adjustment?
    #26
  7. bikecat

    bikecat Long timer

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    Thanks for the replies. This is the first time that I took apart the cylinders so I am careful not to mix up both sides (noob here); I am sure that with experience it will be easy to differentiate the two sides. I also read up and it seems that the rocker arms and valves are not interchangeable left/right sides. Great pointers from all. :clap

    The valves will be re-seated and I've sent them to a machinist to get that done.

    Meanwhile, I did some work on the pistons. Kinda got carried away on the left one:

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    It seems that there is some markings of engine capacity / piston direction on the piston's surface. There's also something that looks like a "$" sign?

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    Right one:

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    The right one has an interesting pattern of wear, anything I should be concerned about?

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    When I was cleaning the right piston, I found this ....

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    So an order is out for a new set of rings. Looks like it's more than just pushrod seal replacement :)

    Cheers
    #27
  8. kraut.burner

    kraut.burner "Fun Club" President

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    fantastic :rofl
    #28
  9. Jasper ST4

    Jasper ST4 Guest

    The arrows go forward obviously, the dollar signs are for if you eff it up.:D That wear is interesting, wonder if it's related to the busted ring?
    #29
  10. supershaft

    supershaft because I can

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    I guess that busted ring didn't gouge the bore? I would be sure and check the ring groove. New rings don't help much with wallered out ring grooves and it's that top groove that often wears. It's always the top side of the groove. You can see the wear if you look closely. If you run a feeler gauge all the way to the bottom of the groove you won't measure any wear because the bottom of the groove doesn't wear. It only wears higher up where the ring is.

    I have seen a lot of nasty looking and even hammered in exhaust seats still seal perfectly but they still needed attention. I wouldn't be surprised if those exhaust guides are looser than a goose.
    #30
  11. bikecat

    bikecat Long timer

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    The broken ring was still in place, so I guess it did not affect the surface of the piston.



    Exhaust guides? Is this something I can check during valve clearance or I have to address it now? Thanks loads.

    Cheers
    #31
  12. supershaft

    supershaft because I can

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    I meant the surface of the cylinder bore.

    Rings do effect the piston's ring grooves! I would call that the surface of the piston. Ring grooves have specs just like the rest of the stuff in question.

    Knowing the specs is one thing and taking accurate measurements is another. It takes skill, tools, and experience. And then it takes some experience knowing what top end specs BMW pulled from outer space and what specs work here on planet Earth.
    #32
  13. bmwrench

    bmwrench Long timer

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    Those look like Black Diamond valves to me. The black coating often wears on the stem, particularly at the bottom and to a lesser degree at the top-which is where all valve stems wear. It doesn't seem to hurt anything as the stem itself is supposed be nitrided. The thing to watch for on these valves is transfer of guide material to the stem. If this is the case, both valve and guide should be replaced. If no metal has transferred and you measure clearance, be aware that this assembly needs at least .003" clearance to survive.

    The right piston crown indicates that it has had water in it-probably from the crankcase vent. I'd bet that the top ring started to rust to the bore at some point and that the ring broke when the motor was started.
    #33
  14. bikecat

    bikecat Long timer

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    Some history might help. The bike stood in tropical weather for nearly 3 years between 2003 to 2005 and then another 3 years in the workshop while the rebuild was taking place.

    This is a steep learning curve for me (I have no mechanical background), and I am grateful for the advice given.

    Cheers
    #34
  15. supershaft

    supershaft because I can

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    Have you seen Black Diamond valves with the stems so perfectly polished before? I haven't. I don't think I have ever seen any that didn't flare the keeper grooves quite a bit as well. Were the keepers ground short so the valves didn't rotate? That's the trick to getting crappy wearing keeper grooves to last longer.

    I have set up MANY a BMW airhead guide with WAY less than .003 stem/guide clearance. They worked perfectly AND let a LOT less oil by for a lot longer time. Hellfar, I have set up MANY a BMW airhead piston/cylinder with less clearance than that! Don't get me wrong, I am not big on real tight guides on most engines but airheads don't have seals and it makes a big diff! The ONLY way to run tight guides, or even looser guides IMO, is to size them yourself with a Sunnen valve guide hone. IMO, all other methods are comparatively a like using a chisel. Most people don't have access to a cylinder dial bore gauge let alone a guide dial bore gauge. IMO, measuring both with anything else (of course it takes micrometers to use the bore gauges) is a joke.

    I bet you're right on about that right piston. That isn't wear. It's corrosion.
    #35
  16. bmwrench

    bmwrench Long timer

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    My post about valve stem to guide clearance applies to Kibblewhite's "Black Diamond" parts, not OEM or other aftermarket parts, and only the exhaust side at that.

    Yes, tight guide clearances, where they will work, are a Good Thing; better oil control and valve sealing, leading to longer-lasting valve jobs, less noise,etc.
    #36
  17. Padmei

    Padmei enamoured

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    Bloody interesting stuff guys keep it going. If the valve guides are rooted how are they replaced?
    #37
  18. wirewrkr

    wirewrkr the thread-killer

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    That "dollar sign"
    is just the makers mark. It is a K on top of an S which mean Kolben Schmidt
    pardon my German spelling.
    Kolben means piston
    #38
  19. supershaft

    supershaft because I can

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    Smokey Yunick said that he found tight guides causing power loss through oil suction. I think I know what he is talking about but is is hard to explain. He does a good job of it. Tight guides might also reduce valve seal because they don't allow the valve room to find the seat's center. I have never noticed any leakage caused by that while leaking down hot engines with tight guides but . . . . At any rate, the upside of tight guides outweigh the downside in our engines IMO.

    I don't understand why you would run Black Diamond valves if you have to set up the exhaust guides well on their way to being worn out for them to work from brand new?
    #39
  20. bikecat

    bikecat Long timer

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    While waiting for my piston rings, I took time to clean the cylinders. Interesting, they seemed similar except for the print "GILAROONI 1" AND "GILAROONI 2" at the base of the cylinders:

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    There might be also similarities in the "5S C" on the "1" cylinder and "?? C" on the "2" cylinder.

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    What are these? Does it differentiate between left and right?

    Inside the cylinders there are lines and I'm told that they look normal.

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    Cheers
    #40