Sunbeam S7 questions

Discussion in 'Classic Motorbikes' started by Kes Green, Jul 3, 2003.

  1. Kes Green

    Kes Green Guest

    Anyone ever had one of these? I've always like the looks. but have been put
    off by criticisms of the handling and the worm drive (and the cost!). Any
    advantage to buying one in the USA and bringing it back?
    Kes Green, Jul 3, 2003
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  2. Kes Green

    Platypus Guest

    I've often wondered about that worm drive. Like, a worm drive is a
    one-way thing: you can drive the pinion with the worm, but not vice
    versa. Think of the machine heads on a guitar - don't exactly unwind
    under string tension, do they? If you did something foolish like
    finding a false neutral, or pulling the clutch lever in, presumably the
    back end would lock up, as the shaft wasn't being driven. Possibly
    there's a freewheel of some sort.

    VN800 Drifter, R80RT
    BOB#1 SBS#35 ANORAK#18 TWA#15
    Platypus, Jul 4, 2003
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  3. Kes Green

    Hog Guest

    That final drive is a terrible weakness (1) and there is no getting away
    from it but otherwise it's a lovely SOB.

    (1) if not using hard or high miles doesn't matter?
    Hog, Jul 4, 2003
  4. Kes Green

    Platypus Guest

    I've just dug out an article[1] on the S7/S8, which reckons that the can
    of worm would become uncomfortably warm in everyday use, and would wear
    out completely in a few hundred miles on the sports model.

    [1]Gurt British Motor Cycles of The Fifties by Bob Currie, twa squids
    from the local cheap bookshop a couple of years ago.

    VN800 Drifter, R80RT
    BOB#1 SBS#35 ANORAK#18 TWA#15
    Platypus, Jul 4, 2003
  5. Kes Green

    Kes Green Guest

    I believe it does have a car-type freewheel, I've also read that there's no
    engine braking (to reduce wear on the worm drive teeth) so it must
    disconnect when you throttle off I suppose. I think that's why the bike
    goes all over the place when you blip the throttle. Anyway, it does look

    Kes Green, Jul 4, 2003
  6. It's quite possible to make a worm drive that works on over-run and many car
    manufacturers have done it. Probably the ratio involved has something to do
    the reversibility. They do tend to need special oils though, you can't
    chuck in any old gear oil and expect to get away with it. Peugeot, who only
    gave up worm drive on cars in about 1965, used to specify a castor base oil
    made by Mobil, though probably old fashioned thick Castrol R would have
    worked OK.

    Ron Robinson
    R. N. Robinson, Jul 4, 2003
  7. It it a true worm drive, though - or just a short one? I'm thinking a
    short one might be able to over-run. Perhaps it's a hypoid bevel and
    mis-called worm.



    GS 850 x2 / SE 6a
    FUB KotL OSOS#12? UKRMMA#19
    Grimly Curmudgeon, Jul 4, 2003
  8. Kes Green

    R Strong Guest

    I know nothing, but a pal had them and swore about the brakes a lot.
    R Strong, Jul 13, 2003
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