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  • Challenger/Silverstone oil seal

    A question for those racing a Challenger or Silverstone. The timing side oil seal does not seem to get any lubrication due to the large diameter spacer between the main bearing and the oil seal carrier. Whenever I pull this seal out it is dry (and worn!), even after a few races and despite lubricating it on assembly. Has anyone overcome this by any means like scalloping the spacer (I believe it is hardened) to allow oil to reach the seal. Apart from wearing quickly it must rob the motor of some power.
    Thanks, Stan

  • #2
    T/S Oil Seal

    Stan,
    This was a known problem, Chris Goodfellow told me that the comp shop used to try and divert a drop of the main bearing oil onto the seal but I can't remember how. Your way seems as good as any.

    I think you'll still have to replace the seal at regular intervals though.

    Druid

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    • #3
      I used to pack the seal and the bearing carrier on my Challenger with a very thick sticky blue grease before fitting the seal. If my memory is correct it was made by Evinrude for lubricating outboard motors. It certainly worked on the Challenger. I used to regularly work on that engine for many other reasons but never for a failure of that seal.

      David.

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      • #4
        Thanks for the replies, guys. Will take a closer look at this over the winter. A labyrinth seal seems like it might be a good alternative if I can fit one in. Have given it some thought about using Honda 50 piston rings.
        Just back from our last race of the year at St Eustace, Quebec. The Greeves won the Period 1 250 race to win the series by one point after a first event DNF due to a coming together and a subsequent highside
        Stan

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        • #5
          You've got me thinking now. I've got a Silverstone engine kicking around somewhere with a labyrinth seal but I can't remember which side. It also has Krober ignition. Will try and find it.

          Changing the seals was a regular job for me back in the day, along with cleaning the piston rings (and checking the pri chain).

          I found that you ignored regular maintenance at your peril!

          Looks like Greeves are still winning!

          Comment


          • #6
            I had a 24MX4 once that had piston rings as oil seals. It worked just fine, and with less friction, but of course you have to machine grooves in the crankshaft to accommodate them, which strikes me as introducing an unnecessary weakness into a competition engine.

            Griffon crankshafts could break just behind the Stefa flywheel...
            Colin Sparrow

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            • #7
              Labyrinth Seal

              Some considerable time ago I discussed this with Brian Wooley who used labyrinth seals on a Silverstone. He didn't machine the crankshaft but used an aluminium bobbin running on the shaft and employed Honda 50 piston rings.

              I believe I reproduced the discussion as an article in the Leading Link, as I say, a long time ago.

              My old copies are hidden in the loft, if someone has ready access to the old mags perhaps he'd like to reproduce it on the forum to help poor old Stan out.

              Druid

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              • #8
                My idea on the lab seal was to machine an aluminum (sorry, aluminium) piece to slide over the crank with the grooves machined in the OD for the piston rings to fit in, probably with a couple of O rings in the bore to give a good seal. Then the whole seal assembly could be slid over the crank and the rings compressed into the bore of the case, after the cases are assembled together. I can't remember now but I think a thin wall steel sleeve may be required in the bore of the case to suit the OD of the Honda rings, would need to suss that out again. I figured that this might even mean it would be possible to eliminate the steel spacer, so giving a bit more room for the lab seal.
                I will have to look at this again now the season is over.
                Stan

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                • #9
                  Oops, we crossed replies, Druid. I have LLs going back to #30 so I will do a search using Colin's useful index to see if I can find it. It sounds like Brian's seal is very similar to what I was thinking.
                  Thanks,
                  Stan

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                  • #10
                    I found a write-up by Rob in issue #39 describing a set of Silverstone cases he had at the time (1991) that had been modified to use lab seals on both mainshafts and also a Krober ignition. The description of the seals sounds the same as I was thinking, maybe that was were my idea came from (it's a bugger getting old). I do remember reading an article by Brian Wooley on the Silverstone in an early edition of Classic Racer where he mentioned making a lab seal using Honda 50 rings but there were no other details.
                    I couldn't find anything else on lab seals from the LL index but there may be something buried in one of my issues. It will be a good excuse to spend a few evenings rereading them all when we are up to our necks in snow this winter!
                    If I find suitable rings I will attempt to make something up this winter to fit behind the PVL ignition I fitted a few years ago, although the seal holder/backplate is the same as the original so the design should be interchangeable with the standard ignition set-up. If it works I will share this with the GRA.
                    BTW, when I pulled out my index of LL articles I see it was Rob who put these together, sorry Rob.
                    Stan

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                    • #11
                      What is the purpouse of the thrust washer? The crank is located axially by the ball race behind the drive sprocket

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                      • #12
                        Challenger oil seal

                        I believe the washer is to stop the cage and rollers moving out of position.
                        Druid

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                        • #13
                          Ahh that makes sense. With the Nametab bearing conversion it isn't needed

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                          • #14
                            As you say gribs, thrust washer not needed, the endfloat is dictated by the ball race behind the primary drive sprocket, but even with new good quality bearings, once run a while endfloat is quite considerable static, but running, trues itself, at least thats how it goes on the griffons...
                            Last edited by dave higgins; 05/12/2014, 11:58 PM.

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                            • #15
                              I didn't get around to sorting out a labyrinth seal for the timing side of my Silverstone as I figured I would have to remove all or most of the spigot on the ignition back plate that carries the existing seal to make space and this was a one off, machined to carry the PVL system I have been using for a few years now. Difficult to put the material back if the lab seal didn't work out.
                              Anyway, when I stripped the motor at the end of last season the TS oil seal was dry, despite changing it once during my 4 weekend race season. The seal lip had disappeared and some seal material had melted onto the crank! That would account for having to keep going up in main jet sizes during that last race weekend.
                              When rebuilding the motor for this year I decided to try and improve the lubrication to this seal and change the seal material to a higher temperature spec. I drilled 8 x 5/32" diameter holes equi-spaced on a 1.450" PCD in the steel spacer (it is not hardened as I thought it was). These aligned with the gap between the outer sleeve in the case and the aluminium bearing cage. The holes were carefully chamfered on both sides and I made sure there were no burrs that might break off and enter the bearing. I bought Viton seals to replace the standard Nitrile seals, that although 3 times the price are still peanuts in the scheme of things.
                              So, having just completed my 2nd race weekend I pulled out the seal to change it and found it was in perfect condition and there was lots of oil present. I have always used R at 20:1 so that hasn't changed. I replaced the seal anyway as I had bought several spares.
                              It looks like holes in the spacer allows lubricant to reach this seal and, although not as sophisticated as a lab seal, it seems an easy remedy to the problem of lack of lubrication.
                              Stan

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