1980 Yamaha 400 Special Countershaft Oil Leak

Discussion in 'Motorbike Technical Discussion' started by mpgmotors, Nov 29, 2006.

  1. mpgmotors

    mpgmotors Guest


    I got a Yamaha 400 Special (vertical twin) bike in today and after a
    few hours of fun chasing the electrons to herb them the right
    direction, "it fired right up". After clearing it's throat a few times
    it started to run pretty well. That is when I noticed the puddle of oil
    spreading on the floor.

    The oil is coming out from the countershaft seal when I rev it up. If I
    take the sprocket off, I can see a little coiled wire around the shaft
    behind the rubber seal that looks like it popped out of the seal. The
    sprocket was loose on the shaft but tightening it didn't stop the leak.
    I saw in an off road forum, that it is possible to pull out the old
    seal and force a new seal in without splitting the cases. Does anyone
    here think that will work? The bike isn't worth a lot of effort but I
    hate to throw out a running machine - even if it leaks like a sieve.
    The shaft has some play in and out of the case, maybe an eighth of an
    inch or so. Not sure if it should do that so I wanted to mention it.


    mpgmotors, Nov 29, 2006
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  2. It's called a "gaiter spring". It helps the lip seal work.
    No, it wouldn't. The oil seal has to hold the oil in.
    You might try drilling two small pilot holes in the metal part of the
    oil seal, opposite each other, maybe 1/8th of an inch from the edge.
    Then screw two sheetmetal screws into the oil seal and pull on them
    with two pairs of pliers. If you can get the old seal out, you can
    position a new seal and gently tap it into place with a homemade seal
    driver, perhaps made of large diameter PVC pipe.
    If you go to www.partsfish.com and register, look at the TRANSMISSION

    The countershaft is in the upper right side of the diagram. It's the
    shaft with one gear machined onto it.

    # 31 is called "circlip 1". It's like half a piston ring, and it keeps
    the countershaft bearing from moving laterally.

    # 25 is called "washer plate". It keeps the countershaft from moving to
    the right.

    # 29 is called "shim 2". It keeps the countershaft from moving to the

    If somebody has split the cases previously, and left any of those parts
    out, that would explain excessive free play of the countershaft.

    Too much free play in the transmission can result in shifting problems
    and the transmission may pop out of gear inconveniently.
    Potage St. Germaine, Nov 29, 2006
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