R75/5 Valve adjustment, pushrod and rocker arm question

Discussion in 'Airheads' started by khale, Jan 27, 2013.

  1. khale

    khale ride dirty

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    Hey guys,
    I just finished up a valve lash job on my r75/5 at 56,600 miles and noticed by left side exhaust push rod wasn't lining up completely straight with the screw end of the rocker arm. Is this normal?

    I adjusted the inlet to .10mm (.004 in) and the exhaust to .20mm (.008 in) on both sides. I've read elsewhere that people adjust inlets to .15mm. Is there a poll anywhere on ADV for inlet valve clearance gap on r75/5's?

    Left side, looks off?
    [​IMG]

    Right side, looks correct
    [​IMG]

    Is this a symptom of a larger problem? I did notice the left side pinging slightly loudly than the right side when I started the bike back up.

    This image from Duane seems like the rocker arm/push rod alignment looks correct
    [​IMG]
    #1
  2. disston

    disston ShadeTreeExpert

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    I don't see a problem with the push rod alignment.

    I used .10 mm and .20 mm valve adjustments for a long time. I think my /6 runs better with .15 and .20 which I currently use.
    #2
  3. bmwrench

    bmwrench Long timer

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    The rocker arms can be moved around quite a bit in the cylinder heads you have. They should be set up so that the rocker tip is inboard of the center of the valves tip. This reduces valve guide wear and noise and keeps the rocker from rubbing the valve spring.
    #3
  4. khale

    khale ride dirty

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    Any tutorials on how to do this? I loosened the rocker arm shaft and attempted to move it to align it better with the push rod with no luck.
    #4
  5. khale

    khale ride dirty

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    It's not so much the pushrod as it's the angle the rocker arm seats on the push rod. Do you see in the first pic how the exhaust rocker arm creates a slight angle rather than a straight line like the exhaust (and inlet) rocker arm to pushrod in image 2?
    #5
  6. khale

    khale ride dirty

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    Here's a line drawn on the angle the pushrod to the rocker arm I'm referring to that's concerning me. The ball end of the push rod still sits flush in the socket end of the screw, it's just not perfectly straight like the others.

    [​IMG]
    #6
  7. disston

    disston ShadeTreeExpert

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    So the left exhaust rocker is rotated around more to get the correct valve lash? All these pics were taken with that particular side at TDC for setting? I see now what it is you are talking about. I don't know that you have a problem. The one thing we are told to watch for is exhaust settings that change a lot or too fast. This can indicate a valve seat that is receding too fast.

    So when you set the valve lash was this valve tight? Did it take a lot of adjustment to get the right gap? Has it been a long time since the last valve adjustment?

    I think it may be wise to remove the heads and check the valves and seats. Maybe a more knowledgeable inmate can correct me.
    #7
  8. Houseoffubar

    Houseoffubar HoFmetalworks.com

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    My observation would be the POSSIBILITY of a receding valve, that previous valve adjustments have been compensating for. Notice how screwed out the adjuster is? this causes the rocker to tip much more toward the pushrod, giving the impression the valve is too long. Since it was probably not originally installed too long, it would appear to be receding.
    Or.... it's a....never mind I'm not clever enough to come up with something entertaining, sorry!:dunno
    #8
  9. khale

    khale ride dirty

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    I'm probably going to get a few chuckles and reprimanded by you inmates for this one... This was my first valve job I have done by myself on my bike (valve jobs have been done before, just not by me). I didn't realize that valve lash adjusting was a diagnostic tool to see what maybe wrong with the bike, rather than a mechanical procedure that actually effects engine performance. So I didn't record or measure my inlet/exhaust lash gap for either cylinder when I first took off the valve covers, thus not knowing if the gap was too tight for inlet/exhaust. :eek1 What I plan on doing, and correct me if I should do otherwise, is put another 1,000 miles on the bike, pull the valve covers and check the valve lash gap again.
    The last valve lash adjustment was around 6k miles ago, or 2+ years. I don't put more than 2-3k a year on this bike.
    And before anyone asks, yes, I was at TDC/OT for each cylinder I was checking; the pushrods could be rotated on the side I was adjusting.
    I used this guide and Hayne's as a reference:
    http://w6rec.com/duane/bmw/valve/index.htm
    #9
  10. khale

    khale ride dirty

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    I could also just be overthinking it too much, and it's just the positioning of the exhaust rocker arm in TDC on this cylinder.
    #10
  11. disston

    disston ShadeTreeExpert

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    I'm afraid you would be well advised to not put another thousands miles on her before further investigation. It sometimes takes us a day or so to get up to speed but I see now what I did not see at first concerning the rocker arm. There is no adjustment left or very little. Either one of two things appears to be happening. Either the exhaust seat has eroded or the ehaust valve on the left head has started to wear severely. I would like to further say that you may just be in time to save this engine but this is not something that is just a little over the edge. It appears from here you have something very serious going on.

    Here's a web page put up by inmate Anton Largiader that shows some pretty serious valve wear;

    http://www.largiader.com/articles/valves/

    There are many other pictures around of valves set too deep in the heads but for whatever reason your exhaust valve is set too deep in that head. This makes the tip of this valve set higher and the adjustment gets used up. When these screws are at the end of their adjustment they are already in danger of having a broken valve. The valve could break before you get to this point it is only luck that has kept you running so far.

    Do you have the tools to take the heads off? Do you have the tools to take the valves out? Depending on where you live a place to work off the street and indoors will be helpful. Get your wallet out. The heads are going to have to be sent for rebuilding. Where do you live? There may be somebody that we will recommend for this work close to you.

    One more word of caution. This work should be done by somebody with experience in Airhead work not your corner machine shop.

    I'm sorry for the bad news. Maybe somebody will tell me to shut up and go away but that doesn't change the condition you have there. Sorry.
    #11
  12. khale

    khale ride dirty

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    More food for thought: I used a heat gun on my bike when I buttoned it back up and the left side (the side I'm concerned about) is running about 50F hotter than the right side. Does this indicate the exhaust valve of concern is about to crap out? Jetting is stock and the same on both carbs.
    #12
  13. disston

    disston ShadeTreeExpert

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    You mean an Infra Red Thermometer? The temp of the cylinders can be varied by small turns of the mixture screws or other carb variations. I think 50* is a big difference. Big enough to be concerned about. But we have no data relating this to what is happening with your valves. I have one of those thermometers also but they are a relatively newer type of tool for Shade Tree Mechanics like myself.

    Do you have a wrench suitable for removing the exhaust flange nuts? The large fined things holding the exhaust headers on. You need the tool for this and you will need a suitable torque wrench for 25 ft/lbs to put the heads back on. Parts for just getting the heads off and back on are going to run ruffly $100. The cylinder head work and parts for that is extra at this point but plan on close to $500 for rebuilding the heads. Sometimes less but I give you the upper limit this time.

    The only way to know what is happening with your valves at this point is to take the heads off and if you have a suitable valve spring compressor you can remove the valves. However all the work to do this has to be done by a shop skilled in Airheads head rebuilding so sending the heads out for service is the first or the next step.

    Think about this. Everybody else will be home later today and they will give you some other opinions, maybe.
    #13
  14. khale

    khale ride dirty

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    Thanks for your help. My brother has a healthy supply of Airhead tools. We are going to investigate the valves tonight as I think that's the first order of business from your advise.
    #14
  15. chollo9

    chollo9 Screwed the Pooch

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    I recently had the same problem (start with post #38 to avoid annoying jibber-jabber):

    http://www.advrider.com/forums/showthread.php?t=830576&page=3

    Exhaust valve adjuster was at its limit. Pulled apart to find a burnt exhaust valve and seat, but honestly I expected worse. Heads are currently at bmwrench's for whatever is needed to bring them up to snuff.
    #15
  16. Bill Harris

    Bill Harris Confirmed Curmudgeon

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  17. khale

    khale ride dirty

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    Thanks. In the event that I need new seats, do you recommend sending off to bmwrench? He seems to be the go-to airhead machinist in the country.
    What can I expect to pay for 4 valves, guides, seats, etc? I'll replace the valves myself, just need a machinist to press the seats in the heads.
    Should I be looking to do the whole she-bang as this inmate did?
    http://www.advrider.com/forums/showthread.php?t=533058

    Is it good practice to replace all the valves, guides and seats at once, since the engine is at 56k miles?
    #17
  18. disston

    disston ShadeTreeExpert

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    Khale,

    I've been getting by on a second set of heads but will be right behind you in the cylinder head refurbishing pretty soon. So I'm not an expert.

    I believe the exhaust seats are the ones that get replaced. Intakes run cooler and don't have a problem.

    I think the rest of the work has to be checked before knowing if it all gets done or just some of it. Has your brother done Airhead valve work before? You seem to trust him. The heads are heated up, very hot, and the old guides driven out and new guides driven in. Then the guides are reamed. Sometimes the intake valves might be reused. But having 4 new valves also sounds nice.

    If you are really looking to make some improvements consider adding dual plugging while the heads are being tended to.
    #18
  19. chollo9

    chollo9 Screwed the Pooch

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    bmwrench has an excellent reputation, and is on the east coast.

    Dunno the cost yet, it is what it is--e.g., genuine BMW exhaust valves are $150 each.

    I'm for replacing what needs replacing.
    #19
  20. chasbmw

    chasbmw Long timer

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    If you are doing the work, replace the exhaust valves and guides as a service item. The valve heads can and do drop, which can be very expensive.
    #20