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how do i know the size of my clutch disc/plate?

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  • how do i know the size of my clutch disc/plate?

    well, obviously, by looking at it, but i'm looking to buy parts before i take it all apart so i can put it together before forgetting where it all goes. i figure, if i'm inspecting it, i might as well replace the wearable parts.

    anyway, 51 champion. i heard some are 9 1/4", 9 1/2" and up to 10".

    could someone give me an answer or a point of reference?


  • #2

    According to S.I. catalog, 8" is for standard duty and 8,5 " for heavy duty. If your clutch is a heavy duty model, you should find a confirmation in your production order. I've experienced personnally several clutches that were modified or equipped with incorrect parts. I strongly suggest not to order before checking the size and all the components of the clutch. Also, don't hesitate to have the flywheel redone. A bad clutch is a real pain in the back.


    • #3
      Take LOTS of pictures as you take it apart. Keep the parts organized and hardware together (ziplock bags are good). The clutch is not all that bad though. Most stuff only goes in one way. On these cars there is almost no point in pre-ordering parts before you tear it apart. You almost always will need something else and have to track it down and wait anyway.



      • #4
        nice to know.

        what's the process in having the flywheel redone? just take it to a brake shop or something? about how much would that run? i'd like to be able to save up to do this all at once!


        • #5
          The flywheel may have burnt or real shiny (hard) spots on it, like this.

          If it does, then machining the face with a bit or turning tool (like in most brake lathes) may require removing extra material just to get thru the hard spots and permit creating a smooth surface.

          Refacing by grinding will allow minimal material removal.

          No matter which method is used, Material must be removed uniformly from around the face to preserve balance.

          On some flywheels the surface that mates with the crank flange face is in a pocket or recess.

          If so, fixturing must be used that supports and references that surface should be used for machining.

          Plonking the flywheel down on the grinding table can result in machining the face true to some arbitrary surface, and result in a wedge shape when from viewed from the side, and unbalance.

          If I was satisfied with the high rpm engine smoothness, Before I took the flywheel in for re-facing I'd measure the flywheel thickness at 6 locations around the edge, expecting all the measurements to be within 0.002 inch or so. Regardless, I'd make a map of the measurements, and ask the shop to check to be sure that original face runs true in their setup before starting machining.


          • #6
            Any competent machine shop should be able to do the job properly. I paid 50 euro for having mine resurfaced. I guess that would be cheaper in the U.S. as you have more machine shops than here. By the way, don't forget to change the little bushing at the center of the flywheel till you are there. Plunge it in motor oil for one day or two before installation. It'll last longer.
            If you doesn't change the clutch pressure plate, you should also check the fingers height and adjust if necessary.