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  • Silverstone/Challenger Crankcase seals

    Hi All,

    I'm restoring a 1967 RES Silverstone to running condition. Possibly racing condition if all goes well.

    Some pictures here: http://www.davidnorwich.com/GreevesRES.htm

    I'm currently having trouble sourcing the crankcase seals. I've searched the forum and spent a considerable amount of time on the internet trying to track these down, but can't find any. Can any member point me in the right direction?

    The forum despite my frustrations in sourcing replacement parts has been a thoroughly enjoyable browse. There is so much knowledge to tap into in this forum. All credit to you guys.


    David.

  • #2
    Hi There,

    Try Nametab engineering on 01527 522266 ask for Simon, or Villiers services should have them on 01384 265797 ask for Steve.

    Good Luck

    Scott

    Comment


    • #3
      Thanks I'll need it Scott - luck that is.

      I haven't fiddled around with bikes for some years. It's a very steep re-learning curve. The Silverstone is a very simple machine that is awkward at times to work on. I've just discovered the cylinder can't be removed to get at the piston without removing the complete engine. The engine is situated forward and the barrel is very close to the beam, preventing it being rotated the necessary 90 degrees to lift the barrel off.

      I'm sure my 250 Challenger upper end could be worked on with the engine in the frame? Or is my memory of that wrong?


      David.

      Comment


      • #4
        Originally posted by 46T Sprocket View Post
        Hi All,

        I'm restoring a 1967 RES Silverstone to running condition. Possibly racing condition if all goes well.

        Some pictures here: http://www.davidnorwich.com/GreevesRES.htm

        I'm currently having trouble sourcing the crankcase seals. I've searched the forum and spent a considerable amount of time on the internet trying to track these down, but can't find any. Can any member point me in the right direction?

        The forum despite my frustrations in sourcing replacement parts has been a thoroughly enjoyable browse. There is so much knowledge to tap into in this forum. All credit to you guys.


        David.
        Hi David,

        The Challenger engine takes a 35x47x7 or 35x47x10 on the LH main. On the RH side it takes a 25x40x7.

        Good luck with your RES.

        Regards,
        Ken Sykes
        USA

        Comment


        • #5
          David,

          The barrel comes off OK without taking the engine out. I raced Silverstones back in the day and still have one.

          My barrel came off more than once in the paddock!

          Just put the piston at the top of its stroke and lift the barrel clear of the crankcase studs. Tip it back and then turn it and lift off. You only need to make sure the barrel is turned before the inlet port reaches the piston rings.

          Regarding seals, the ones Kenny gives for the Challenger are identical for the Silverstone. The drive side is the same as a Ceriani fork seal (and possibly Bultaco). They are common seal types and you may find that a local bearing supplier can supply them.

          Looks a great bike!

          Rob

          Comment


          • #6
            Thanks guys. The seals are the sizes indicated by Ken. Easily located on the internet from bearing suppliers as Rob stated.

            Rob,

            On your Silverstone is there a small port at the rear of the barrel? It comes into view just before BDC. My Challenger barrel only had four.


            David.

            Comment


            • #7
              David,

              On one of my barrels there is. This is non-standard and I believe is known as a 'boost port'. There is a corresponding window in the piston to match it. The only other Greeves I have seen that on is the American-spec Nick Nicholson TT Challenger barrel.

              Don't know how experienced you are with the Silverstone but if you want any hints or tips just send me a pm. They are easy to break compared to a trials or road bike (but more fun)!

              Comment


              • #8
                My RCS had no boost port, but the Silverstone replica did. No discernible difference in performance though.

                With a boost port you find yourself carefully cutting and filing a matching hole in the back of each and any replacement piston. Bit of a pain.
                Colin Sparrow

                Comment


                • #9
                  Originally posted by Rob View Post
                  David,

                  On one of my barrels there is. This is non-standard and I believe is known as a 'boost port'. There is a corresponding window in the piston to match it. The only other Greeves I have seen that on is the American-spec Nick Nicholson TT Challenger barrel.

                  Don't know how experienced you are with the Silverstone but if you want any hints or tips just send me a pm. They are easy to break compared to a trials or road bike (but more fun)!
                  That's very kind of you. Likely you will get a few PMs!

                  I know very little about working on this particular motor but it is not that different to the Challenger I used to ride from 1969 -1973.

                  The GP carb is a whole different ball game though! Based on the research I've done, I think I have it set up correctly and I'm just waiting on those seals arriving to finish building the motor up to have go at starting it.

                  The pilot jet has two holes in it just below edge where the needle exits. The replacement from Amal doesn't have any holes. I'm wondering what difference these holes make and what they are actually there for?

                  David.

                  Comment


                  • #10
                    Originally posted by Colin Sparrow View Post
                    My RCS had no boost port, but the Silverstone replica did. No discernible difference in performance though.
                    With a boost port you find yourself carefully cutting and filing a matching hole in the back of each and any replacement piston. Bit of a pain.
                    Hi Colin,

                    Who built the Siverstone replicas?

                    It seems odd that time was taken to design and manufacture this port, that in actual use it made no difference.


                    David.

                    Comment


                    • #11
                      Silverstone

                      That jet with two holes in the sides is a 4 stroke jet when used in concentrics and the one with no holes is a 2stroke jet when used in a concentric and the both have their own needles to suit, probably same applies to a GP carb...John P.

                      Comment


                      • #12
                        Silverstone/Challenger

                        The boost or "finger" port was not designed for the racer, it was intended for the Challenger and was "designed" at the request of Nick Nicholson, Bearing man will either confirm or deny this.
                        I don't think it made much difference on the Challenger and even less so on the racer.
                        Nowadays it's difficult to find a standard Silverstone barrel as all the "tuners" have been at them with their files.
                        People should realise that the Silverstone was never a Yam beater but it gave novices an intro to racing without bankrupting them.

                        Druid

                        Comment


                        • #13
                          Originally posted by 46T Sprocket View Post
                          Hi Colin,

                          Who built the Siverstone replicas?

                          It seems odd that time was taken to design and manufacture this port, that in actual use it made no difference.


                          David.
                          We have about 10 of these barrels in stock. According to Gordon Jennings who wrote the book "Two-stroke Tuner's Handbook" The design came from MZ to cool the piston crown and carry up oil to the wrist pin...what they found out was an increase in power as well.

                          Kenny Sykes

                          Comment


                          • #14
                            Originally posted by Bearingman View Post
                            We have about 10 of these barrels in stock. According to Gordon Jennings who wrote the book "Two-stroke Tuner's Handbook" The design came from MZ to cool the piston crown and carry up oil to the wrist pin...what they found out was an increase in power as well.

                            Kenny Sykes
                            Kenny, does that mean MZ found an increase? Presumably then they had found a restriction in the system that meant the existing transfers were not passing what the disc was allowing in, whereas the Greeves was restricted by the piston ported inlet, so adding the other port made no performance gain.

                            Comment


                            • #15
                              Originally posted by 46T Sprocket View Post
                              Hi Colin,

                              Who built the Siverstone replicas?

                              David.
                              Mine was a one-off which had started life as a 24MX5C. No idea who converted it, but it was very nicely done. See LL 75. I think it had a re-ported long-stroke Challenger barrel; Druid's remarks explain the existence of the boost port.

                              It actually handled quite well because it had about 2" longer wheelbase than a "real" Silverstone. I might still be about, it did get debated on here when it came up for sale a couple of years ago.
                              Colin Sparrow

                              Comment

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