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Primary chain tension - QUB 380

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  • Primary chain tension - QUB 380

    Hello folks,

    Engine almost ready now - but one question - how much slack should be left in the primary chain? I am assuming a few millimetres (5 to 10?)at the mid point of the chain run to allow for engine/gearbox case expansion when hot? Is that about right?

    Also, I've lock wired the bolts holding the chaincase to crankcase (tab strip was missing), also the gearbox to engine bolts. Are there any others I should wire?

    I'll put some pictures up on the site soon - when there is something worth photographing!

    Once again, thanks for the help.

    Tony

  • #2
    Just to be clear........5 - 10 mm movement in the chain up and down - not front to back!

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    • #3
      Tony,

      Certainly the gearbox to crankcase bolts need wiring. I didn't bother and the gearbox nearly fell out at last year's Christmas Cracker! The bolts very quickly came loose and fell out.

      Years ago, a chap in our local chalkpit had the throttle stick open on his 380. The vibration was such that the gearbox end cover screws came loose and the oil ran out as he tried to get the plug cap off!

      Wire verything you can!

      Cheers,

      Rob

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      • #4
        griffon bolts

        We no all about that Rob!

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        • #5
          From experience with the Works bikes , I used a plain washer , then a shakeproof , dab of loctite & then wired the chaincase & gearbox bolts .

          This because of seeing the gearboxes & chaincases come loose on the Griffons that were presented to the Press at wakes Colne .

          The bikes were not prepared in the Comp Shop but elsewhere , I never lost a chaincase or gearbox on the ones I did .

          Chris

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          • #6
            Thanks to all, I shall take heed of these wise words.

            Also, I've now put a couple of photographs up on the site. I'm still learning about how to do all this Forum stuff, so have not yet fathomed out how to put a link in here, but they are definitely there.

            I would welcome any comments about the 4 fin barrel. I've been fortunate in being able to talk to the original builder who says that contrary to what they thought would happen, it actually ran 25% cooler than standard. He was pleased because it took two weeks to grind the other fins away.

            Are there other examples around like this?

            Tony

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            • #7
              Originally posted by riflegreen View Post
              From experience with the Works bikes , I used a plain washer , then a shakeproof , dab of loctite & then wired the chaincase & gearbox bolts .

              This because of seeing the gearboxes & chaincases come loose on the Griffons that were presented to the Press at wakes Colne .

              The bikes were not prepared in the Comp Shop but elsewhere , I never lost a chaincase or gearbox on the ones I did .

              Chris
              Hi Chris - very interested in your post here...I am continually getting problems with bolts working loose....I have solved the gearbox to crank ......but last meeting the chaincase to crank bolts worked loose and I also noticed the main primary drive bolt and clutch mainshaft bolts also starting to work loose...despite use of loctite and spring washers.....I am just re-building ready for Sunday at Marks Tey and will try your suggestion on the chain case bolts but do I need the plain washer as well as the shakeproof and does it matter which one first??.....

              Also - I will try shakeproof washers on the primary drive and the clutch mainshaft as well.
              Many thanks in advance Cheers Kim

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