Rear wheel turns even with Clutch depressed

Discussion in 'The Garage' started by McVick, Oct 25, 2009.

  1. McVick

    McVick Been here awhile

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    Hi,
    This is curious, anyone have an idea of explanation?

    Bike - 1988 Honda NX650

    The rear wheel continues to recieve drive even when the clutch lever is depressed.

    I just replaced the clutch cable and adjusted it appropriately.
    I have the bike up on a stand so I decided to start it up and make sure everything is running smoothly since I just replaced the two sprockets, chain and rear tire....

    With the engine running and the bike in 1st gear and the clutch lever depressed the rear wheel spins. Same for all the gears, depressed the clutch lever and shifted through all the gears, rear wheel still spins with clutch lever depressed. Granted it is spinning slowly and does not seem to be accelerated by throttle with the clutch lever depressed.

    Is this normal?????

    I thought the clutch lever should completely disengage any gearing when depressed just like in a car.

    Thanks
    Brian
    #1
  2. P B G

    P B G Long timer

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    Many bikes the wheel will turn clutch in or in neutral, while on the centerstand.

    There's some amount of drag between components in the transmission, and that can transfer rotation.

    I would imagine that while the bike is off the stand it doesn't drive forwards.

    And I would guess that if you ride it around till warmed up and put it on the stand it will turn less.

    As the viscosity of the oil is less when hot, and that will make it thinner, and in turn less drag, and less movement.

    This is also the reason alot of bikes will "clunk" into first from neutral when cold. The clutch needs to break free and the oil warm up before everything performs like it should.
    #2
  3. concours

    concours WFO for 48 years

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    just normal internal drag. Multiple plate wet clutch is markedly different than the dry, single plate in a car. Try it with the wheel on the ground and be prepared for unexpected motion in case you've effed up the clutch job.
    #3
  4. McVick

    McVick Been here awhile

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    Thanks guys,
    I was hoping that was the case, makes sense.
    It does not look like there would be enough drive to move the bike forward when on the ground.

    Thanks for educating a newb!
    #4
  5. LuciferMutt

    LuciferMutt Rides slow bike slow

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    Yes.

    It's the oil drag of the wet clutch. It acts a tiny bit like a torque converter in an auto transmission.

    Nothing to worry about.

    Watch YouTube for videos of people demoing a new exhaust -- many times the bike will be on a stand and when they rev up the engine in neutral or with the clutch squeezed, the rear wheel will turn slowly.
    #5
  6. A_Vasiliev

    A_Vasiliev Red, white and blue.

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    That doesn't seem right. Doesn't neutral mean the actual tranny gears aren't engaged, meaning the clutch and any oil viscosity between the plates are besides the point?

    :deal
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  7. P B G

    P B G Long timer

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    Its not that they are engaged in neutral, its that they are all next to each other, with oil between them, and they aren't far apart, they are sort of sitting against each other dragging.

    And as is often the case they are Constant mesh designs as well meaning the gears are in engagement, and they have to be "linked" to the output by the means of sliding collars.

    So your clutch drags a bit even when pulled in, your gears drag a bit even in neutral, and your wheel will turn a bit, even in neutral with the clutch in.

    BUT you will find you can stop the wheel fairly easily.

    I would even suggest that if your wheel doesn't turn a bit you probably have something too tight, chain tension, wheel bearing preload, or the bearings aren't very smooth. Something to check.
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  8. LuciferMutt

    LuciferMutt Rides slow bike slow

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    Probably because in neutral, the clutch is engaged, and the input shaft is spinning inside the hub of a gear -- it's just that the dogteeth are not engaged on that particular gear. Same thing, oil drag/component drag causes the output shaft to spin slowly. A car on stands would probably do this if there weren't so much drag in the differential and brakes.
    #8
  9. P B G

    P B G Long timer

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    This is what i mean by constant mesh

    [​IMG]

    All gears always together, when you shift there are collars between the gears with lobes on their sides, those lobes slide into the gears "locking them" which is what controls which gear you get. But note in neutral the input shaft spins inside the gears, which they all turn the same direction so the additive friction can cause it to turn.

    Also this is why I commented that when warm you see it less, the oil inside gets warm and thin and everything spins easier.
    #9
  10. A_Vasiliev

    A_Vasiliev Red, white and blue.

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    Ah, PBG and Devil, thanks for clearing that up for me. :ear
    #10