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  • @68 isdt

    I have one of the four Greeves prepared by Comerfords for the '68 British ISDT team. It has been kept as original as possible and I do not want to alter its originality, but its b****** noisy and not really suitable for a lot of events- I am making from scratch(!) a tail pipe silencer but is there any other solution? Also, its based on a Challenger so has a close ratio gearbox- are there any other choice of wider internals?

  • #2
    Peter
    Re exhaust, 2 things you can do.
    1) Repack the 'silencer' part of exhaust with new fibre glass (loft insulation) you will of course need to cut it open to do this and then re weld. I would think there is a perforated tube running through the centre with the fibre glass packed round it. I have not had experience with a Challenger but have done a similar mod with roadster exhausts to good effect.
    2) You could fit an auxiliary 'stinger' silencer to tailpipe, these are available from various motorcycle component stockists and dealers.

    Cant help with gear ratios, looks like you have the standard scrambles ratios, I presume a wide ratio set were fitted for ISDT use.

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    • #3
      Isdt

      Don't cut it open no perf pipe in here you say you don't know about Challenger so why give duff answers again more rubbish stick to 4T.

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      • #4
        You could simply get a quieter exhaust and fit it and keep the original safe somewhere.

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        • #5
          Used to love the Crack, from the open exhausts at the Scramble meet, I was taken to as a kid.
          Also Exeter speedway, standing trackside, goggles on, being covered in 'Cinder' as the riders came round our corner.
          I remade my Trials Greeves exhaust to conform to modern event standards.
          Do drop off the 'Stinger' Tail pipe at home some times, because
          Get one made with a re packable end section, then I can be cleaned once a year, to conform to the 'Greenies'
          But maybe, unlike John, I no absolutely nothing about Challengers, so will be probable asked to stick to the Trials section of the forum.

          whitehillbilly

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          • #6
            Originally posted by anglian man View Post
            Don't cut it open no perf pipe in here you say you don't know about Challenger so why give duff answers again more rubbish stick to 4T.
            Come on, keep it friendly please.
            Colin Sparrow

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            • #7
              Originally posted by anglian man View Post
              Don't cut it open no perf pipe in here you say you don't know about Challenger so why give duff answers again more rubbish stick to 4T.
              Anglian Man if you know about this exhaust system why dont you give Peter Greig some constructive advise as to how to reduce the noise on his bike instead of slagging me off.
              Not a duff answer as the system could be modified to incorporate an absorption silencer (perforated tube and fibre glass wool packing), but looks like the easier option would be to fit an after market 'stinger' silencer to outlet, my second suggestion.

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              • #8
                I had the same problem with my ISDT challenger exhaust being too loud so I saved the original and bought a replica exhaust pipe from CW classics http://www.cwclassic.co.uk/gallery-bike-parts/ for £180 which took 4 week for them to fabricate. The tail pipe or stinger was a larger diameter than my original exhaust so I was able to fit an internal baffle (as suggested by Stace on this forum) which I bought off ebay https://www.ebay.co.uk/itm/1pcs-48mm...wAAOSwL3JawzHy and packed it with wadding. It is a lot quieter now and looks just as good as the original. The replica challenger exhaust pipe was painted using a spray can of high temp matt black used for painting barbecues that I bought from my local DIY store. Just make sure that if you buy a challenger exhaust from CW Classics that you tell them what size diameter your header pipe is (or better still send your header pipe to them so they can snuggly fit the exhaust to it without any air leaks at the joint). Although CW Classics say that the new challenger exhaust pipe comes with an internal baffle already fitted; it is just as loud as my original so I had to fit another baffle in the tail pipe.
                Attached Files
                Last edited by pgc40; 10/07/2018, 08:33 AM.

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                • #9
                  I changed my close ratio gears for wide ratio for my mx2 ISDT challenger with the help of Druid on this forum and it is much better for enduro type riding. The close ratio gears I believe are much sought after for motocross racing so you may be able to do a swop with some one on this forum. A lot of Greeves challengers in the USA have wider gear ratios for trail riding so it may also be worth speaking to Kenny Sykes aka bearingman.

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                  • #10
                    '68 ISDT Challenger

                    Peter are you sure your bike has the close gear set because it was originally built with wide ratio gears. I believe Paul Gollings at Villiers services still has some of the wide gears. Email me if you need more info.

                    Greeves did modify the silencing on these bikes by stuffing a Volkswagen baffle tube up the exhaust.

                    Druid

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                    • #11
                      I donít know much at all but Iíve used a chrome end pipe off a vw Bettle before on a greeves Scottish,fitted inside greeves silencer

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                      • #12
                        VW Beetle tail pipes readily available and cheap https://www.ebay.co.uk/itm/VW-Beetle...YAAOSwG-1W0D35

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                        • #13
                          We Built this MX5 clone for a customer who was going to ride it in the ISDT reunion ride. My attempt was to make it quiet as possible without adding a large silencer. Since the pipe was made from scratch, we lined the inside with perforated metal cones and wrapped these with fiberglass silencing cloth. On the exhaust tip we used flexible stainless tubing with slots cut in it and again wrapped it with more fiberglass cloth. For the tail piece, we used an FMF USFD approved spark arrestor that is used in a modern four stroke exhaust. While it looks the part and fits really well, it's still a little noisy to my disappointment as a lot of work went into the fabrication. I should have used more cloth, but did not want to turn the power into a total slug.

                          Kenny Sykes
                          Nicholson Motors
                          Attached Files

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                          • #14
                            Isdt

                            Ooh! that's put the cat amongst the pigeons! 1. I am making a stinger style tailpipe silencer, more details, photos etc when (if!) it works. 2. Without dismantling the gearbox & counting teeth I believe I have a close ratio box- you would expect a wide ratio to be chosen, but the riders in those days did not hang about so...Ö? I understood that this bike was not b****** about with it, although it was running on 13/1 ish comp ratio when I got it, you would change that before replacing gearbox internals, and I have. I want it useable in modern surroundings, but to be returnable to original by unbolting the era bits.

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                            • #15
                              My theory is that you need to add some packing in the expansion chamber and a box on the end. If you look at other manufacturer's ISDT bikes, they have very big chambers. This suggests to me that the "free" area in the chamber must be maintained for efficiency and the packing added outside the expansion area. The Challenger exhausts were very small in comparison to other makes, with the resultant crack being noticeable. If originality comes before function, then it seems a problem for road or modern enduro riding.

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