Consistent False Neutrals

Discussion in 'Old's Cool' started by Mike D, Jun 24, 2011.

  1. Mike D

    Mike D Corporate Cog

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    '76 R90S

    [​IMG]

    Consistently getting false neutrals, mostly between 4th & 5th, but sometimes between 3rd & 4th. Always on the upshift, never on the down.

    I always catch the false neutral with the clutch, and am able to disengage the clutch, lift the lever again, and it catches. I'm not worried that I'm doing any damage.

    I've searched the issue, and have a question:

    Someone posted that I should try, when shifting, continuing to hold the shift lever up while engaging the clutch; the theory being that the gear will catch as the clutch is engaged.

    Seems to me that greatly increases the risk of grinding gears, or straining the whole system by engaging gears with a partially engaged clutch.

    Is this a recommended practice? Or, should I just accept, and plan for, the false neutrals that really aren't hurting anything?

    Thank you in advance for your wisdom...
    #1
  2. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    Interesting. Whenever I hit a false neutral, I can't just pull the clutch and shift it up.. If I try to, I can feel gears starting to grind. I have to shift it back down into a gear and try again.

    But, of course, this is of no help to you.. :lol3
    #2
  3. stainlesscycle

    stainlesscycle Long timer

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    is there slop in the linkage? is everything tight? everytime i catch a false neutral on any bike it's usually sloppy lever or linkage. unless it's a bultaco, then it's always a box full of neutrals.
    #3
  4. Beater

    Beater The Bavarian Butcher

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    1. When was the last time your splines were lubed?
    2. Tranny ever seen work? rebuilt? When? how many miles since?

    I see a false neutral on the upshift, but mine is 2nd to 3rd. I 'preload' the shift arm by applying a bit of pressure to the shift prior to squeezing the clutch ... then squeeze and continue to apply pressure with the foot until I can feel the tranny is completely in gear ... only then releaseing the clutch. This seems to help me. I have 120K on the non-rebuilt tranny too ...

    I have heard of increasing occurances of false neutrals with the splines (tranny to driveshaft) becomeing dry ...

    Good luck.
    #4
  5. bmwblake

    bmwblake upside down parker

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    you kinda hit on this in your original post. it's somewhat hard to get this across in text, but i would guess that you just aren't used to shifting an airhead.

    push up on the shift lever a bit before pulling in the clutch, continue upward to shift, release clutch, release shift lever.

    you can't just click through the gears. think of it more like a tractor and less like a honda. :D
    #5
  6. Arkwright

    Arkwright Grumpy ole Git

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    It's quite simple, after the first change from first to second ................STOP USING THE CLUTCH........................., just roll the throttle off slightly and change up............its a DOG BOX not a synchro box.............it doesn't need the clutch..............when you get used to it you'll be amazed how easy it is, and you won't do it any harm. The same applies to going down the box particularly in the higher gears, roll the throttle off slightly to take the load off, then slightly blip the throttle as you change down it's very easy when you get used to it. I started doing it when I had exactly your problem, I discussed it with my Airhead mentor (who showed me how to rebuild my box) who explained it to me and I haven't looked back since! I even do it on my 12 now!
    #6
  7. Mike D

    Mike D Corporate Cog

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    You are right, I'm not used to shifting an airhead, this is my first one (have an 1150GS that shifts quite well, comparatively :lol3).

    I'll try that technique. Thanks
    #7
  8. Mike D

    Mike D Corporate Cog

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    Seriously? No clutch after the shift from 1st to 2nd? (I understand what you're saying about the throttle blips, makes total sense)

    Shifting without the clutch will cause the universe to implode, right?

    Being a rookie airhead owner, I'm sorry for questioning you, but....

    Does anyone else agree with this?
    #8
  9. rufusswan

    rufusswan Been here awhile

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    Not saying that I agree with it as a "best practice", but before gearboxes got synchros they were called "crash boxes" and he is describing the correct method of shifting the old things.
    #9
  10. hardwaregrrl

    hardwaregrrl ignore list

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    Preload the shifter. it just works.
    #10
  11. Mike D

    Mike D Corporate Cog

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    Yea, I've done that. It just doesn't.

    EDIT: Thought that would come off as funny - - it just doesn't :) Thanks for that advice, but I've tried it, and it doesn't help. It works on my 1150GS, but doesn't solve the problem on the R90S.
    #11
  12. P B G

    P B G Long timer

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    You can certainly do so, and it can be quite handy if you are occupied trying to stop a carb leak whilst accelerating onto a road.

    I would say it is best to learn the technique on someone else's bike. A rental perhaps.
    #12
  13. hardwaregrrl

    hardwaregrrl ignore list

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    Bummer. I have the same problem on my ST after a rebuild. It's the only way I can shift it into second.
    #13
  14. bmwblake

    bmwblake upside down parker

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    jenna is saying the same thing i was but in a much simpler manner.
    you can't really compare an oilhead and airhead gearbox. the airhead will require a bit more focused preloading, or maybe your gearbox is buggered?


    #14
  15. JonnyCash

    JonnyCash turd polisher

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    Really? On an airhead? On my RD I shift clutchless all the time, but on my R100s/5, it just doesn't seem right. Between 4th and 5th I sometimes do, but it just has never felt right on any of the other gears. Maybe I'm just too clumsy, but I've always felt that the gearbox was kind of clumsy.
    #15
  16. danedg

    danedg Horizontally Opposed

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    You've absolutely, positively, guaranteed that your gearbox is full of fresh new 90W?....:ear
    #16
  17. Arkwright

    Arkwright Grumpy ole Git

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    All BMW boxes are 'Dog' boxes the later ones just have a more sophisticated selector mechanism and all will change clutchlessly, you just have to be gentle but positive (if that makes sense!). The other thing that helps is a shorter shift lever with a roller arm on the end as supplied by 'bmwboxersupplies.com' and others like 'Migsel', less movement makes for a more positive change.

    To be fair it took me the best part of a year to perfect the technique properly, but you cant do any damage by trying, you engaging 'dogs' not gears and if you haven't taken the load off it won't move anyway!
    #17
  18. Jasper ST4

    Jasper ST4 Guest

    The gear box is clunky and different than most others. I tell people that it's German, you order it into gear. I always use the clutch and I've got 167,000 trouble free miles on it so far.

    But I mostly wanted to say that you have a very enviable machine! Someone put some love into that. The only thing I see, and I'm not an expert on the years, is the spark plug caps. Was the '96 equipped with the rubber 5k ohm ones? They may have updated the ignition to electronic but you can get 5k ohm metal capped wires.
    #18
  19. Sanders

    Sanders Stogiesuckingsinglemalter

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    I don't know about the shift thing, my 90/6 does exactly the same thing between 4 and 5, so I'll be paying attention.
    I really just wanted to say this is a pretty nice Airhead for your first one. I'm seriously envious, and I sported a little sumthin' in my britches when I saw her picture...
    Just sayin' :wink:
    #19
  20. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Gorgeous bike!

    I'm not certain I understand your problem with the false neutral. I get the idea it feels like it's in gear, but then pops out. Or is it that you let out the clutch and you're not in gear at all?

    These bikes do shift differently than most others. With the heavy flywheel, dry clutch and the jacking effect you've got some interesting dynamics to deal with. And it is a dog transmission - meaning it doesn't use synchromesh to bind the mating gears together (and align them while shifting) but dogs. Dogs are pegs protruding from one side (four or five of them) of the gear that mate to holes in the adjacent gear. This locks them together.

    Getting closer to your problem, some of the dogs are stepped. By this I mean a few of the gears have dogs that increase in diameter half way down. I guess if the dogs were the larger diameter clear to the end, it would be more difficult getting into gear.

    Anyway, how this relates is that it's very easy (especially for new airhead riders), to feel like it's in gear when in actuality it's only half way there. And it's very easy for the gear to pop back away from its mate as the clutch is letting out and pressure applied to it, thus your "popping out of gear" or false neutral. When shifting, you can feel the extra little force half way through and will know when it's all the way home.

    But it seems to me the stepped dogs are only on third and fourth. Not fifth.

    If the transmission input splines are dry the disc can drag and not engage easily, but usually causes a problem in lower gears and getting out of neutral.

    In the early 80s the shifting ramps were changed with more of a peak to help give more force to the shift forks forcing the gears into position. But once you understand these transmissions and have a feel for them you won't need all that upgraded stuff.

    The heavy flywheel in these bikes makes for interesting shifting - along with the jacking effect. What happens is the back of the bike rises when you get on the gas, and comes back down when you let off. That energy gets transferred to the gears and so you've got a situation of the engine not dropping RPMs very quickly, and on the back side, the output shaft being pushed by the final drive.

    The solution is to back off the throttle a little BEFORE PULLING IN THE CLUTCH, which will settle the rear end and remove pressures on the gears. Then, once everything is free of tension, with a little pressure on the shifter, pull in the clutch and it'll practically shift itself. Done right, it's almost effortless.

    But with the heavy flywheel bikes, don't expect to shift fast unless you've got a real feel for it and get everything matched up just right. And I wouldn't shift without the clutch though it can be done - I had to once when the clutch cable broke. But one of the major reasons these transmissions need rebuilding is metal particles from the dogs contaminating the oil. The smoother the shift, the less metal in the oil - I don't want to chance the possibility of grinding those dogs.

    If it's not any of the above and you still have problems, then it's either a case of shimming in the gearbox, or the shifter mechanism, maybe worn dogs. But I've got a feeling it's just your getting used to this foreign mechanism. My first beemer had been shimmed very badly with way too much play and was easily the worst shifting transmission I've ever met. Add that to the complexities already mentioned and you've got a real mess! It took me a couple years to figure out how to shift the thing smoothly most of the time. With that beauty of yours I can't imagine it being anywhere near that horrible.
    #20