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little hole in clutch pressure plate

Discussion in 'The Garage' started by xjwmx, Apr 3, 2011.

  1. xjwmx

    xjwmx It's just the unknown. Top Contributor

    Why does the little hole in the clutch pressure plate have to line up with the mark on the piece behind it? It looks all symmetrical to me. Did they balance it lined up with the mark at the factory?
  2. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    The hole is used to aline the pressure plate teeth with the gaps in the clutch centre grooves. If they are misalined, the teeth will partially rub against the clutch centre grooves, resulting in plates not pulling in fully and clutch slipping.

    There is a wrong rotary position and there is a right rotary position, thats why the index hole is there.

    Nothing to do with balancing.

    If you count the teeth, there are 29 teeth. When you divide 29 into 360 degrees, you get 12.4 degrees between teeth. The spring bosses are 60 degrees, so you can rotate the pressure plate every 60 degrees. The problem is that 12.4 degrees does not divide evenly into 60 degrees. If yamaha had used 30 teeth, then the rotary position would have repeated every 60 degrees, and there would have been no need for the index hole. I think Yamaha used 29 teeth just to make it a little challenging for re-builds.

    Attached Files:

    Last edited: Apr 3, 2011
    gggGary and DanielBlack like this.
  3. xjwmx

    xjwmx It's just the unknown. Top Contributor

    Ah ha! I didn't pay close attention to it when it was off, because I was going to put it back with the marks lined up regardless :)
    Last edited: Apr 4, 2011
  4. Great explanation retiredgentleman :cheers:
  5. itsagivens

    itsagivens itsagivens

    I pulled the side cover and the clutch plates and I can`t see any marks on my `72. I put new plates in from MikesXS, it said to use 6 metal and 7 fiber, which I did. Now what? This 40 year old is kickin my ass!!!!!
  6. I don't think the early style had splines on the pressure plate so no hole.
  7. itsagivens

    itsagivens itsagivens

    Your right no splines,found two tiny bumps, lined them up still wont disengage!!!
  8. XSLeo

    XSLeo XS650 Guru Top Contributor

    I don't think the spring bosses are at 60 degrees. When you put the pressure plate on in the right spot the threaded holes for the spring screws line up centered in the spring holes. Turn it one notch and they don't. At this point the pressure plate rubs on the places were the threaded holes are.
    This rubbing can prevent the pressure plate from moving as far as it should. This can keep the pressure plate from putting pressure on the clutch plate, it also makes the lever pull harder.
    If no marks try it in a few posions and find where they allthe spring screw holes are centered in the spring seats.
    This will make more sence when you look at the parts.
    gggGary likes this.
  9. itsagivens

    itsagivens itsagivens

    Thanks Leo I`ll give that a try!!!

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