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A7, A10 BSA gearbox on a Challenger.

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  • A7, A10 BSA gearbox on a Challenger.

    Hi,

    Can any member off me some advice on fitting a BSA A7, A10 gearbox to a Challenger engine?

    I'm particularly looking for information on what clutch to use. I was led to believe that a Griffon type clutch was a direct fit - but that is not the case. The Greeves clutch I have has a 5 spline fitting. It's a 6 spline on the BSA.

    I've seen these gearboxes fitted often to a Greeves but information online is non existent.

    Thanks,
    David.

  • #2
    David, There are two centres for Griffon clutches. One, 5-splined for Challenger boxes and a 6-splined for late Griffon boxes, Jack Knight gears I believe. I have both types, one on the Silverstone and the other on a late Griffon engine and box. Colin

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    • #3
      As a note of interest, I fitted the plunger frame bolt up BSA gearbox shafts to Gold Stars back in the sixties as it allowed the use of a Norton clutch,when Goldies were common in club racing. So perhaps a Norton clutch might be an alternative. Colin

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      • #4
        Ahh right. Now I know! This one came off a Silverstone Albion 5 speed gearbox. This special I'm building is starting to get complicated. I sorely regret selling you that Greeves 4 speed box now! It would have made the whole job much easier.

        Regards,
        David.

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        • #5
          I had thought of that but I would be in the dark about the whole idea. From what I see online. Norton clutches are a bit pricey.

          Originally posted by Dogsbody View Post
          As a note of interest, I fitted the plunger frame bolt up BSA gearbox shafts to Gold Stars back in the sixties as it allowed the use of a Norton clutch,when Goldies were common in club racing. So perhaps a Norton clutch might be an alternative. Colin

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          • #6
            A10 gearbox on a Challenger

            The first Challenger gearbox was so bad that riders took to fitting the plunger A10 box just to get a reliable ride. Not too difficult to fit the box but the primary took a bit of work. Both the Norton clutch would fit the spline, or, using a S/A A10 mainshaft you could fit an adaptor to use the Triumph clutch. Both clutches were superior to the A10 clutch basket with the floppy studs.
            Back in the '60s both A10 gearboxes and Norton clutches were cheap, not the case now.
            The ratios in the std box were a bit wide for the 250 Challenger, the scrambles ratios (sc) were better but are now like hen's teeth and cost about £600 for a box. The best option really is to find a box off an MX5 or 360 and use that with a Griffon clutch if you intend to race the bike.

            Druid

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            • #7
              Thanks for the reply. It's a road bike project I'm working on.

              I have the close ratio box. I've just completed re-building that. I must have been lucky. The box and parts where not that expensive or difficult to source.

              I want to use the original chaincase - so If anybody has a 6 spline Greeves clutch for sale or a complete gearbox please get in touch.

              David.

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              • #8
                I am fitting an A10 box to a 360 engine for my new sprint bike. The gearbox bolts straight to the engine. I have modified the housing by having a couple of bits welded on around the end cover mounting face so i can fit the swing arm type end cover. This will allow me to fit a Nova 5 speed cluster. I will be using a Bob Newby clutch with belt primary drive

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                • #9
                  Yes it's a straight forward enough job.

                  You are keen..... Nova gears are 2k plus.

                  David.

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                  • #10
                    Yeah but how much is a 5 speed cam barrell Albion that may be knackered?

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                    • #11
                      That's assuming you could find one. You could have had my fully working one one for a lot less.

                      Just had a look at Bob Newby's website. Nice work!
                      Last edited by 46T Sprocket; 05/05/2015, 10:42 AM.

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                      • #12
                        Just had a chat with Simon Bateman. Nametab. He has a 6 spline clutch and shaft to copy and plans to offer a 6 spline clutch centre at some point. So that is at least one possible option for the future if all else fails.

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                        • #13
                          There was a 5-speed Nova cluster on ebay a while back, new unused, went for about 1600 I think. I reckon BSA/Nova is the way to go if you want long term reliability and easy to find spares. There is a guy near me who is going to make close ratio BSA gears soon, but only 4-speed. The plus side is that he reckons a 4-speed close ratio cluster will be about £600.

                          It is possible, with a huge amount of work, to use a Triumph 5-speed box inside the BSA 'box. I think Roy Shearwood did one a few years ago.

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                          • #14
                            Result!

                            Phoned Geoff Nunn after speaking to Simon Bateman and by pure chance he had just removed a 6 spline centre from a clutch to fit a 5 spline centre and had the 6 spline one spare. Reasonable price too. So I'm a happy lad and my project is back on track.

                            Geoff's not on the internet though. "That's a dark art to me Dave!" Bit like gearboxes are to me then Geoff!


                            David.

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