Clutch Clutch works Motor Runs No Motion.

Discussion in 'Transmission / Drivetrain' started by will_start, Jun 29, 2010.

  1. will_start

    will_start Member


    Bike stopped.

    Clutch works to start motor, motor runs.
    But I try and engage engine, and get no motion.

    Took off clutch cover, and small cog still engages engine
    with a push forward.

    i think something is broke inside.

    o o o
    Last edited by a moderator: Jul 2, 2010

  2. AussieSteve

    AussieSteve Active Member

    Does the clutch slip at all when you're starting it?

    First, as you're considering, try adjusting it.
    It wouldn't hurt to remove the top clutch plate and visually check the pads, while you're at it, too.

    It's odd that it grips to start, but not to run....
    If the clutch all seems OK and adjustment doesn't help, it's possible that one of three woodruff keys has sheared, but is still working like a ratchet. (Not a big deal to fix.)
    The countershaft sprocket has one, the primary drive gear on the RHS of the crankshaft has one and the clutch has one.
    (Also one on the magneto rotor, but that's not the problem.)
    You'd need to remove them one by one to check.
    Do you have a clutch/countershaft sprocket puller?
    Last edited: Jul 1, 2010
  3. will_start

    will_start Member

    I may have a sprocket puller somewhere.

    The clutch doesn't slip when starting.

    A. countershaft sprocket.
    B. primary drive gear on the RHS of the crankshaft.

    would I need to take motor apart to do this ?
    Would that require special parts once it is apart ?
    EG motor seals etc.
  4. O.K.

    First things first:

    Is this the first build you have done.

    It sounds to me like your engine isn't firing just think it is because it's making a Brrrrrrr noise when you release the clutch.

  5. AussieSteve

    AussieSteve Active Member

    Jim, it's not a new build. It's been running for quite a while. (will_start can tell whether or not it's running.)
  6. Strange...

    It can only be something similar to what you had originally a ratchet effect...that is definitely a new one on me...but then again it's Chinese...:biggrin:

  7. Start the engine...give it gas...the engine revs freely and is no longer engaged to the rear brain is still trying to figure out HOW!

    I've had a bunch of these seems impossible.

  8. will_start,

    Describe exactly...what happens after you start it?

  9. AussieSteve

    AussieSteve Active Member

    Yeah, it's a new one on me, too, but I can't see any other possibility. What else could make the clutch work only in one direction?

    Only the side-covers need to be removed, the crankcase doesn't neeed disassembly.
    No special parts except a new woodruff key if that's the problem. No seals needed.
    (A woodruff key is a tiny, half-moon shaped piece of metal that locates the gear/sprocket/clutch on it's shaft so it can't rotate.)
    Last edited: Jul 1, 2010
  10. AussieSteve

    AussieSteve Active Member

    Jim, do you know where woodruff keys to fit are sold?
  11. The only keys I can get locally are the SAE standard ones.

    They have to be worked a bit to fit.

  12. AussieSteve

    AussieSteve Active Member

    I just did a search and it looks like most people do that. On my dirt bikes I used to use a piece cut off the right-sized washer.

    I'll check with one or two suppliers for ready-made ones, first. Not sure of the dimensions without pulling my engine down. My MBc search results give varying sizes: 3/16", 1/8", 2mm x 10mm.
    (This is assuming that it is a sheared key. Symptoms are odd.)

    Ha, my failing memory..... I forgot that I had a spare countershaft sprocket and woodruff key sitting here, (and my vernier).

    Dimensions: 2.4mm x 8.9mm x 3.6mm
    Last edited: Jul 1, 2010
  13. AussieSteve

    AussieSteve Active Member

    Woodruff Key Suppliers

    In the US, woodruff keys can be had from, for $3 each, here, (mid-page, RHS).

    I just emailed ZBox in Oz to see if Steve will sell them separately.
    Yep, same price - $3 each plus $6 delivery - got four ordered as spares.
    Last edited: Jul 1, 2010
  14. will_start

    will_start Member

    Start motor as normal, hold clutch in warm engine up.
    peddle, release clutch all the way out and rev engine.
    nothing happens. Its like the clutch is still in.

    IE bike don't move unless I peddle.

    need i say more.

    I made a vid of installing the woodruff key on small clutch cog.
    about 16 years ago on this motor.

    I'll post Utube link if I find/search it and link,
    but don't hold ya breath.

    page 2 of the below.

    That vid has had 3,300 views...goes to show how much
    the woodruff key sucks !!!
    Last edited: Jul 2, 2010
  15. AussieSteve

    AussieSteve Active Member

    Was that really 16 years ago and same motor?
    That's one sweet HT engine.

    On a serious note, your description is exactly how I pictured it. I can't imagine it being anything but a sheared woodruff key, to cause that freewheel effect.
  16. will_start

    will_start Member

    It feels like 16 years ago (jan 08). I use that timeline description, to affect whats happened to me in that time-frame...3 girl-friends, too many dates to mention, 1 job redundancy, 1 divorce, 3 house do the maths.

    If the Woodruff Key I show in the vid is sheared, then the motor will not start.
    So, where are these other mysetrious wood-ruffs A & B, and I need a diagram.
    There was an exploded diagram of the motor on this site somewhere...
  17. AussieSteve

    AussieSteve Active Member

    Quite true, usually, but at times after shearing they grip at times and slip at other times.
    Very possibly, one of yours has sheared and is doing that.

    This is a very unusual problem, as Jim and I said earlier, and it's hard to find an explanation for the symptoms.

    I don't need to watch the video, (PC is faster but I'm still on dial-up for now), the woodruff key that you replaced is the one on the crankshaft.
    It drives the larger cog on the clutch. When the clutch is fully disassembled, there's a nut holding it's base plate-onto the countershaft. When the nut is undone and, using a gear puller, the clutch base-plate is removed, there's a woodruff key that's used to locate it on the countershaft.
    On the LHS, there's a woodruff key locating the front drive sprocket on the countershaft.
    (Also on the LHS, under the front side-cover, is another one used to locate the magneto rotor, as I've mentioned. This couldn't cause the problem that you describe, though.)
    These woodruff keys are identical to the one you replaced before.
  18. srdavo

    srdavo Active Member

    I just gotta ask..... are you pedal starting, or do you use a pull/rope starter??
  19. AussieSteve

    AussieSteve Active Member

    Good thinking Dave.
  20. Stan4d

    Stan4d Banned

    Real curious question. If you pull the plug and roll the bike forward and backward with the clutch engaged does the motor turn. In both directions? After removing covers you might be able to do this and see where the loss is. (On electric forklift final drives,I have seen woodruff keys snap and only slip when powered one direction.)