Shim under bucket

Discussion in 'Parallel Universe' started by Camel ADV, Sep 23, 2010.

  1. Camel ADV

    Camel ADV Long timer Supporter

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    I just checked my valve clearances and they are all within spec (barely). 34,000km.

    Intake Spec: 0.18mm-0.26mm
    Mine are 0.19mm, 0.20mm, 0.19mm, 0.20mm

    Exhaust Spec: 0.27mm-0.35mm
    Mine are 0.28mm, 0.30mm, 0.31mm and 0.32mm

    My understanding is that in a shim under bucket system, as things wear, the clearances get tighter rather than looser like rocker arm set-up. So if things get tighter you would always want to adjust all the way to the high end of the spec so you get the most bang for your buck? With all my current clearances being so close to minimum I'd want to shim right to 0.26mm on intake and 0.35mm on exhaust rather than mid-scale correct?
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  2. TowPro

    TowPro Single Track Geezer

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    I don't know what the so called experts are going to tell you, but if it was me, I would wait until you drop below the required measurement, then change to the next thinner shim which brings you back into specs on the tight side.

    As you add clearance you loose valve opening height and gain noise (valve tap).

    Rocker arm valves also go tight as they "wear". The wear is the valve setting lower in the seat, closing up the clearance.

    I would be more worried about the measurements once you get to the point the adjustment is required more often. This is usually an indicator that the valve is bending or the seat is going bad.

    I know in modern high RPM 4 stroke dirt bikes (like my last TE Husky) you will find the valves stay in adjustment for a while, then start to loose clearance fast. When you get to the "loose adjustment fast" mode, its time for a rebuild before valves break (and bounce around inside the head).
    #2
  3. ebrabaek

    ebrabaek Long timer

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    You have it right. When they move...they usually goes tighter. That is due to the valve coating wearing off, and then valve itself is now wearing....and progressively seating deeper in the valve seat. That causes the stem to move the shim closer to the cam....etc... Tolerances are created to cover the differences in measuring. 10 persons, would get 20 different measuring values.... That said, as long as you are within the tolerances.... I`d leave it right there.... Record the values....And check them again in the next say 5000-10000 km/ miles. If they have now moved outside the spec`s.... Then you move then to the top of the tolerances. When they begin to move...there are usually no way back.... They will continue to wear, since the coating is gone.... Factors that affect this.... Biggest one is dirt ingestion. I`m gonna throw a fireball here......Ride a lot in the dirt with a K&N filter...with out the pre-filter...... If you do have the urge to change the shimms.... Yes to the upper of the spec`s.....:thumb:thumb

    Erling
    #3
  4. Camel ADV

    Camel ADV Long timer Supporter

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    I wasn't really thinking about valve/seat wear being the cause of the clearance changing. I was expecting cam, top of valve stem and rocker contact surfaces wearing down was the reason and was having a really hard time geting my head around the fact they tighten as they wear. It's all clear now!


    Since they are in spec now I understand why you would say leave them. The problem is that we're heading to South America in a few weeks and will put 30,000km on before we get back and if I can avoid having to be ordering and swapping shims while I'm on the road that would be ideal. I'd like to bring them to the top end of spec so they can wear tighter over the next 6 months and then do a re-valve when I get back. Obviously I'll have to check them while on the road a few times.
    #4
  5. itsforrest

    itsforrest Ugly bag of mostly water

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    Just curious, is this the first valve check? If adjusted previously, do you have the numbers from that time?

    Ideally I would adjust them to dead-nuts in the middle of the spec range. They don't always tighten up as they wear, although it seems most common from what I've heard/read.
    #5
  6. reinerka

    reinerka Been here awhile

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    I just did mine as well (24K mile service) and all of them are within specs - as I expected. I don't expect them to change from now on until around the 75K mark. That is when I had to changes on the GL1800 (shim under bucket as well).

    I usually adjusted them back to the middle of the interval and didn't get any additional changes for another ~75K miles before changing them again. Worked well for the 240K miles I had the bike.

    Reiner
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  7. blatant

    blatant Been here awhile

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    here's a question: Everyone that said they've had them checked at 12k, 18k or even 20,000 miles more or less have said they've been fine and not needing adjustment.

    Clearly not a perfect experiment above but could you say from this determination that one could "skip" the 12k mile "valve service" and simply change the oil filter etc? Considering the expense of that service. NOW if you did decide to skip this "crucial" step, per bmw, what would it do to said warranty or what other potential issues or hassles could arise?
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  8. GeorgeinVA

    GeorgeinVA Beemers Uber Alles

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    It would end your engine warranty, BMW sees skipping things as neglect. However I doubt any "real world" harm would be done. I have checked a few dozen F800s (F650 twin) never seen a shim out of spec. Most of those were 12k a few were 24k and less than 5 were 36k. If I owned one the valve cover would never come off unless it was leaking or I noticed a change in performance/ gas mileage.
    #8
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  9. blatant

    blatant Been here awhile

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    georgeinva, thanks, nice to see a small biz owner. I've seen your posts here and there. Good shit. You and joel wiseman should go on a date :flip lol
    #9
  10. ebrabaek

    ebrabaek Long timer

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    As to what I posted above.... I`d like to add this..... When they begin to move due to dirt ingestion..... They move fast......Like ping-pong in say 2-3000 miles... ( hard to say on this motor, but in general), So imho....even if you adjusted them now to the upper limits..... You`d be chasing them all through out Africa. The key is the trend.... Which is an even better reason to check them periodically......rather than to honor the warranty. So if they have not moved....well..... ehh.... since last time you checked them..... I`d personally leave them alone. Make sure you have a good filter in the airbox. If you have one of those metal mesh over gauze filters....:D... You need a pr-filter.....imho. Other than that.... I would leave them alone... They are within spec`s......:thumb:thumb

    Erling
    #10
  11. The Griz

    The Griz Long timer Supporter

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    Very true. Saw this on two brand new K&N BM8006 air filters I received for my F800GS. The scariest part is that I didn't notice it until I got back from a 3,400 mile trip and I went to clean the filter!

    Notice the large openings in the filter material. The biggest opening was about the size of a large piece of sand or a small pebble.

    K&N? Hell no!!

    [​IMG]

    [​IMG]

    I recommend the UNI USA F800GS air filter:

    Model #NU-7308

    http://www.unifilter.com/online%20catalog/streetbmw.html
    #11
  12. itsforrest

    itsforrest Ugly bag of mostly water

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    Holy crap........... you posts............ are hard........... to read...........:eek1


    There was a comparison done on a car forum recently between the OEM Mazda air filter, K&N, BMC, Uni, and two or three others. I found it through a link either here or on F800 riders forum. He tested the air flow on a bench and tested the filtration with a white paper secondary filter on which it was easy to see how much dirt got through. Each filter was tested for the same period in the same or similar conditions. If I remember correctly, each was tested for 5,000 miles of daily driving, no off-road or competition.

    While the gauze filters such as the K&N and BMC did flow a tiny fraction more air, the OEM paper filter was the best of any, including the oiled foam, for filtration. The pre-filters for the gauze filters decreased the air flow more than stock and did not stop more dirt.

    I've used many K&N filters over the years and have one in my car right now. With a ram air intake it is a very noticeable power improvement. However, I wouldn't bother with a drop in for a stock air-box and would never use one in dusty conditions.
    #12
  13. Camel ADV

    Camel ADV Long timer Supporter

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    I checked them when I changed the leaky valve cover gasket a year ago and they were in spec but I don't recall the numbers. I wrote them down but was on the road at the time and that paper didn't make it home with me.

    I talked to 2 bike mechanics at a BMW specialty shop today and one said, "leave them alone" and the other said, "adjust before you go."

    The lazy me thinks "f$%k it, leave them" and the other part of me thinks "do it now so you don't have to do it in the middle of Bolivia and wait weeks for parts.:huh
    #13
  14. ebrabaek

    ebrabaek Long timer

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    Sorry........I did`nt mean to...:jjen......I perhaps should have posted it in the...morning....before espresso...:*sip*
    :thumb:thumb

    Erling
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  15. The Griz

    The Griz Long timer Supporter

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    I've seen that write-up. I think you're speaking of this:

    http://www.bobistheoilguy.com/airfilter/airtest3.htm

    Unfortunately, he doesn't test UNI USA oiled foam. In fact, he doesn't test any oiled foam. Only paper and K&N oiled cotton gauze.

    All I have to say is that I've used UNI USA filters on all of my bikes: KLR650's, F800GS, and DRZ400. No matter how dusty or dirty the conditions are, the design of the UNI foam and the UNI oil keeps my airbox spotless. I mean spotless. Not a hint of the finest dust particle. Every time I remove my UNI USA filters for cleaning, I'm amazed at how clean they keep the airbox. Oh yeah, and when I hold them up to light I can't see through them!!:deal:D
    #15
  16. itsforrest

    itsforrest Ugly bag of mostly water

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    Thanks Griz, I couldn't find that when I searched. I thought that one had the Uni foam in there, too.

    Here is a separate test that does include the K&N, Uni and a few others.

    http://bmwmotorcycletech.info/K%20&%20N.htm

    Note in the accumulative gain that the Uni actually passed more dirt than the K&N.

    Still seems that paper filters are the best for stopping dirt.
    #16
  17. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    Let me start by saying I've never worked on an engine with the "shim under bucket" design, but have worked on a variety of overhead valve engines on cars and a few bikes and I almost always see the clearances getting BIGGER not smaller.

    I realize the valves can wear such that they set "higher" in the head thus reducing clearances, but it would seem that all (most?) of the rest of the wear in the system would tend to make clearances larger ... wear on the cam lobes, wear on the rocker arms, wear on the cam journals, etc.

    Are we sure here that these bikes tend to tighten up with age? :huh
    #17
  18. ebrabaek

    ebrabaek Long timer

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    No.... Not with age..... That nasty symptom..:D...will cause the valves to loosen. After a gazillion miles.....at least on this bike..... But if they wear due to dirt ingestion..... They will get tighter, after the coating wear.......Thy`l go fast......In most all instance..... you need a valve job....:thumb:thumb

    Erling
    #18
  19. itsatdm

    itsatdm Long timer

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    Are we talking F800 here?. If you are, it is not a shim under bucket design.
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  20. The Griz

    The Griz Long timer Supporter

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    I know this sounds stupid, but while reading everything in the link above, I didn't once notice him mention that they actually oiled the UNI air filter. Now, you'd hope/think that common sense would kick in while they were testing. However, I find it very important to mention that those numbers regarding the UNI are typical of what you see with an un-oiled UNI. :deal And for a guy (the guy in the link) that admits that he doesn't have any experience with foam air filters, I must say, I wouldn't put it past him. The UNI relies heavily on the UNI filter oil the capture the dirt. Without the oil, you will see numbers like in the report above.
    #20