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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    Thanks for the help, guys. I really appreciate it. I took off the head last night and here's what I saw. Not as bad as I originally thought. The exhaust and inlet valves are still seating perfectly on their seats. No wiggling or movement on the valves either. No cracks. They just have a lot of carbon build up, which I assume is normal.
    Any advice after seeing this? I don't think it would hurt to have fresh valves...

    Exhaust valve closed:
    [​IMG]

    Exhaust valve open. Hard to see the seat due to carbon build up on the outskirt. The actual seat where the valve rests itself is clean as a whistle.
    [​IMG]
    #21
  2. khale

    khale ride dirty

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    Can someone provide the laundry list of parts I need in order to perform a full valve job on this bike? Parts numbers would be lovely. Looking on MAX BMW for right now.
    Should I go ahead and complete the top end by replacing piston rings as well?
    Forgive any ignorance, my first time doing this...
    I've sent an email to Bud to see if he's interested in putting new seats on my heads.
    #22
  3. disston

    disston ShadeTreeExpert

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    You let the machinist provide valves, guides and seats. New springs are a nice touch and not terribly expensive. You get what the machinist recommends. There are several choices of after market or OEM valves and guide materials. There are threads and surveys here on AdRdier dot Com that have more than a hundred posts and give well into the neighborhood of 3 dozen opinions on how to do this. Nobody is going to digest this and make any sense out of it. If you want to learn how to do BMW Airhead cylinder head work then I suggest you enroll in a BMW Service School. The tools for this work will run into the tens of thousands of dollars and the school will probably be a hundred thousand dollars. After 30 years of messing up other peoples machines I think you may get a refereral or two from some of the Inmates here.

    It is not a list of parts and some pointers off the Web kinda thing. See?

    Your part is called the R&R That is Removal and Replacement of the parts. To do this you need a pair of head gaskets, a pair of base gasket/shims and 4 push rod tube rubbers. You generally don't need things like new valve cover gaskets but when taking things apart you check these to make sure they don't need replacing.

    To see if you might need rings, take the pistons off the rods, take the rings off the pistons and set them in the cylinders to check the ring gap. If rings are with in spec you can reuse them. The pistons can also be checked by putting into the cylinders with out their rings on and checking the fit with feeler gauges. Also wiggle the pistons inthe cylinders to see how well they fit and note weather the cylinder walls are worn in a taper. If you have trouble deciding if you need cylinder or piston ring work then a machinist can measure these things with accurate tools that most of us don't have.

    You must be very careful when removing and replacing piston rings. These are not made to bend and they are easily broken. If you break one ring you will be buying all six too make things right. May in fact be what you need but it's still recommended you don't break the rings. There are special pliers for removing the rings and helping to not break them. I recommend using these tools instead of the finger nails which is usually what we do when we don't have the ring pliers.

    You'll also need a suitable ring compressor tool to put the pistons and rings back into the cylinders.

    If you are doing this much so far then also get the special triple square driver for removing and replacing the rod bolts and replace the big end rod bearings. These are not terribly expensive and are service type parts for our bikes. They get replaced merely because we are there.

    You are going to need a suitable torque wrench for the rod bolts and the cylinder head bolts. The rod bolt toque is in your manual. If you still need it I'll look it up later. The cylinder head bolts are to be tightened to 25 ft/lbs in three stages. Use 25 ft/lbs as the final torque value and disregard any other toque value published anywhere.
    #23
  4. chollo9

    chollo9 Screwed the Pooch

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    If Bud is doing your heads, I'd let him provide anything head related. The rest is just gaskets and such. As for rings, just check the gaps--if they are well within spec, I wouldn't change them (and you won't have to seat them). If they are outside, or close, then a fresh set would be in order (along with light honing).

    My rings were way out, and my pistons are just within tolerance. I decided to let the pistons ride, knowing they will make it at least a year, and go with first over rings, which I will file to get good gaps.

    My thinking is that it's so easy to pull the top-end, I don't mind fudging a little. When I'm sending stuff like heads off to have work done, that's different, I'm getting it all done while it's there.

    Just my way of thinkin', and the budget has a bunch of other stuff in it this winter too!

    (disston replied while I was typing, so . . .)
    #24
  5. disston

    disston ShadeTreeExpert

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    After all the directions earlier I'm looking at the pics of your heads and don't see what the problem is. If the valve is not eroded and the seat is not eroded then why is the adjustment at it's limit?
    #25
  6. disston

    disston ShadeTreeExpert

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    Yes Chollo I'm rather long winded. :lol3
    #26
  7. chollo9

    chollo9 Screwed the Pooch

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    As am I.

    But then I stare.

    And edit.

    Then I appear to be a Man of Few Words.

    Ha! If only.
    #27
  8. disston

    disston ShadeTreeExpert

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    Why is his adjustment at the end? If the seat and the valve look good? Is there something we aren't seeing?
    #28
  9. khale

    khale ride dirty

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    This is really what I'm trying to get to the bottom of... After pulling the head, evidence shows the exhaust valve looks completely fine, worthy of 4 or even 5 digits worth of miles. Why would the exhaust rocker arm adjuster screw be at the end? :huh
    #29
  10. khale

    khale ride dirty

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    Appreciate the thoroughness. This all helps me a lot. I guess I should have stated I'm not entirely a novice when it comes to mechanics, but I'm absolutely not on the level of Click/Clack. I own many tools, including a torque wrench.
    #30
  11. khale

    khale ride dirty

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    When I was putting the head back on last night after inspection of the valves, I put the rocker arm/shaft in place and from what memory serves me, I had room left on the exhaust rocker adjuster screw. I wish I had taken a picture so I could verify it 100%.
    If my adjuster screw does now in fact have room left, could it have meant that I just didn't align my rocker shaft correctly, or anything else? Sorry, I know this is a tricky issue to diagnose.
    #31
  12. bmwrench

    bmwrench Long timer

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    With the adjuster screwed in that far, the exhaust valve has to be sinking into the seat. You can't determine that without disassembling the head.
    #32
  13. photomd

    photomd Been here awhile

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    [deep south southern draw]Don't tell them boys from the UK about a torque wrench. Evidently they have a genetic mutation that enables them to torque by feel. :evil We 'Merican's are the only ones that need torque wrenches.[/deep south southern draw] :D

    IMHO, I'd say button it back up and watch your valve adjustments every 500-1000 miles. From the pictures I've seen, I don't think you need head work.It looks like your valves and seats look good. If there's no wiggle of the valve in the guide with the spring removed and no exhaust blow by, I'd say you're good. If you want another opinion and you're an ABC member, I'd bet you could email Oak for another opinion: that might be helpful. It might be worth running the adjustment issue by him as well.
    #33
  14. Renner

    Renner combustophile

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    I'm guessing this pic was taken with the valve spring in place and somehow compressed... and that no measurement of the valve stem and guide bore was taken...
    I'd like to be wrong in that assumption.

    If my guess is right, then it would be difficult to feel the slop in the clearance, etc.
    It would be a drag to carry on with a worn valve stem & guide till the valve head separates, noisily beating the piston to death, AMHIK.

    but then again it may be fine till the next inspection.

    in the pic, that little bit of valve seat looks sort of recessed... but maybe the image is misleading.
    my best guess is bmwrench has it right.

    The cylinders on my old /5 were so tapered we went from standard to 2nd over, though that engine was running pretty well before I tore it down for head work.
    (not the same engine that swallowed a valve).

    #34
  15. disston

    disston ShadeTreeExpert

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    khale,

    If you haven't put it back together yet can you take a few more pics? You have the valve out from the looks of the first photo. Take pic of seat with out valve and valve out of head. Please.
    #35
  16. chollo9

    chollo9 Screwed the Pooch

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    My head with the same valve adjuster issue looked surprisingly "good" upon disassembly, valve guide wear aside.

    I expected serious seat recession, or heavy valve tuliping but could only see some heavy burning.

    Not an easy thing to measure either, e.g., compared to the other head. I guess it's a sum of a number of small faults, rather than one glaring one--best left to a real machinist, not an amateur like me.
    #36
  17. disston

    disston ShadeTreeExpert

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    I guess Khale has put it back together now so the answer will have to wait.

    I often leave out the story of some of the nonsense I'm capable of. I have mentioned that I have two sets of heads for my bike. I had the original ones off and was trying to replace the rings. I ended up with new 2nd over sized pistons, rings, honed cylinders. And my old worn out set of heads. The main problem with my heads seemed to be the guides were a little too worn.

    I found another set with better guides but worn out exhaust valves, I thought. So I bought a new pair of exhaust valves and lapped them into the seats. That's what I've been running for the past 20K. Runs fine.

    One of these days I will try putting guides in. I need the proper type reamer. I have the other stuff. But I figure both sets of heads now need new seats or that's what I think I want and I know we can't do valve seats. We might do valve guides but it seems few riders do this any more.

    Going to set the valves later today but the main project is to paint the inside of my fairing. Temp will be almost 70* I think. Then it's going to turn Winter again tomorrow.
    #37
  18. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    +1 on Disston and Chollo. Unless you are planning to buy expensive valve tools and add decades of experience, you'll want the shop to do the entire job and not simply press new seats in.

    Too bad we didn't get to see the valves and seats...

    --Bill
    #38
  19. PaulRS

    PaulRS Dutch fool

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    Seat recession, valve tuliping, or valve stem stretching (even breaking) is a known problem on older airheads.

    But another problem is that the posts the rockers sit on creep inwards.
    They are a press/fit steel bushing in the alloy heads and over time they tend to do so.

    So check the height of those posts on the affected side, and compare with the other, which look ok.

    I had similar problems with the heads from my old /5, should have taken a few pic's for posterity, but they ended up in the bin before I thought of that.

    Paul.
    #39