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Old 06-24-2011, 05:56 PM   #16
danedg
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Quote:
Originally Posted by Mike D View Post
'76 R90S



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...

You've absolutely, positively, guaranteed that your gearbox is full of fresh new 90W?....
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Old 06-25-2011, 01:35 AM   #17
Arkwright
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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!
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Old 06-25-2011, 03:40 AM   #18
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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.
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Old 06-25-2011, 03:50 AM   #19
Sanders
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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'
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Old 06-25-2011, 06:21 AM   #20
Wirespokes
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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.
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Old 06-25-2011, 08:09 AM   #21
Bill Harris
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It might be something minor like learning to preload the shift or a dragging clutch or something major like transmission internals.

He needs to let someone experienced in Airheads take a look at it.
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Old 06-26-2011, 08:22 AM   #22
batoutoflahonda
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As mentioned before, try the spline lube. It's simple and something you can do yourself.

I was having trouble getting mine to downshift under a load, and was getting false neutrals on up shifts. Thought the tranny was bad. Lubed the splines a couple weeks ago and it shifts like butter. Who'd a thought.
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Old 06-26-2011, 01:42 PM   #23
Max Headroom
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The "false neutrals problem" sounds more like bent or worn selectors to me, given that the problem is consistent, and only happens with an up-shift. Possibly caused by excessive pre-loading of the gearshift lever when changing gears . . . .

Wirespokes, your accurate overview of the shortcomings with the /6 and /7 gearboxes with the heavy clutch/flywheel, the selector mechanism design and the solid driveshaft remind me of why I went to the trouble of fitting a post '82 flywheel/ clutch, post '86 gearbox internals and a torsion driveshaft to my R90S. Together with correct shimming, gearchanges are welcomed now instead of dreaded, and quiet instead of truck-like.
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Old 06-26-2011, 09:13 PM   #24
Wirespokes
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Quote:
Originally Posted by Max Headroom View Post
...remind me of why I went to the trouble of fitting a post '82 flywheel/ clutch, post '86 gearbox internals and a torsion driveshaft to my R90S. Together with correct shimming, gearchanges are welcomed now instead of dreaded, and quiet instead of truck-like.
Yeah, it's one of the things I love about my newer bikes. I'm thinking of doing the same thing to the 90S myself. However, I don't believe the torsion driveshaft makes any difference at all with shifting. My 84 had one, but had to replace it for some reason I don't recall, and used a solid one instead. It shifted just the same afterward.
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Old 06-26-2011, 09:24 PM   #25
Boon Booni
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Quote:
Originally Posted by Mike D View Post
'76 R90S



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...
My R90/6 used to sometimes pop out of gear immediately upon releasing the clutch after shifting to 5th. I found that when I shifted to 5th, before I let the clutch out, I could hold the shift lever up and would get a second detente after 1/2 a second or so and then it wouldn't pop out.

Fixed it by putting an upgraded ramp kit in the gear box.


Lovely bike by the way.
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Old 06-26-2011, 11:44 PM   #26
Rob Farmer
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Mike D,

Has you bike always done this? It doesn't sound right to me. I've just sold a 78 100RS that had a lovely positive gearbox with no signs of false neutrals. My high mileage 78 100/7 has a nice positive gearbox. It sounds as though yours needs some TLC.

As for shifting without the clutch..just make sure the gears have a chance to spool down. I've seen a couple of these through people changing down through the gears too quickly. layshafts aren't cheap..


Rob Farmer screwed with this post 06-27-2011 at 12:25 AM
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Old 06-27-2011, 08:52 AM   #27
coastranger
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you are facaing major major issues
even still.......Ill give you 500 bucks for it as it sits
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Old 06-27-2011, 09:14 AM   #28
Rob Farmer
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you are facaing major major issues
even still.......Ill give you 500 bucks for it as it sits
What a nice man you are
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Old 06-27-2011, 12:13 PM   #29
yokesman
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I have not been on my buell for sometime, heavy footed the thing, some false shifts. the lever on some of these bikes need to return to their position to engage the next gear.
i need to raise my lever or lower my inflexible 60 yo foot.
just a starter, been away awhile and find i added to the delimmea.
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Old 06-27-2011, 01:23 PM   #30
Mike D OP
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Thanks everyone for the responses, explanations, and compliments. Sounds like I need practice and patience. As I mentioned, this is my first airhead, so definitely not used to the technique required.

I'll try everything mentioned, and if that doesn't fix it, and the problem gets worse, it'll go to a pro.
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