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Thread: Sunbeam 1949 S8

  1. #31
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    Default Re: Sunbeam 1949 S8


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    When you say "like a Commando",do you mean wheel patter,like riding over a wash board?
    This could be fork damping due to lack of oil,or wheel balance,but neither should be critical on this model.
    If the bike had been sitting for some time,maybe with flat tyres,it could be a flat (out of round) on the front tyre.This should sort it's self after a few miles.
    Also check that the tyres are seated even on the rims,if they've been pumped up from dead flat,they could be out of true.
    If you find one that's uneven,deflate it,push the beads in,wipe some tyre soap round the beads and over inflate.This should pop it back in place,then reduce to correct pressure.
    By the book
    FRONT-3.25 X 19 20PSI
    REAR -4.00 X 18 22PSI.
    Both tyres standard profile ie AVON SM's.

    This is for 10 stone rider,increase 1PSI for each extra stone in rider weight.

    With the charge light,as said,first thing to check is brushes,they could be sticking,or if worn the sring tension is too low,and they can bounce as they go over the comutator segments.
    http://www.onthebeam.co.uk/lucas.pdf
    Some old Lucas Regulators have points just for the charge light,and if these are manky,the light will have no relation to the actual state of charge
    You can get photo copies of the old Parts Books and the Munro/Pearson books (workshop manuals of their day) from BMS at around 9.60 each.
    Also think about joining the Sunbeam Fellowship,a good club.


    Lovely bike,enjoy.
    Last edited by FlatheadDave; 19-06-11 at 12:37.

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    Default Re: Sunbeam 1949 S8

    Quote Originally Posted by FlatheadDave View Post
    FRONT-3.25 X 19 20PSI
    REAR -4.00 X 18 22PSI.)
    I seriously disagree with those pressures. They look like original figures from a 1949 handbook. New tyres have softer sidewalls than 1949 ones and work better with higher pressures than that. I like your other ideas about what might cause the wobbles (lumpy tyres etc). Wheel balance should usually show up at greater speed than 45 on big wheels though.
    Last edited by ink ink; 19-06-11 at 13:35.

  3. #33
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    Default Re: Sunbeam 1949 S8

    As I said "by the book",if fitted with Roadrunners,it would be more like 29/33 psi,but how much of that is compound,and how much lower profile,I couldn't say.

    Maybe a call to Stewerts would be the best idea.I see they do a good online Parts Catalogue,and their own Workshop Manual for 8.

    Online Parts Catalogue to Stewart Engineering

    They also have online Tech Info that you can see if you register.

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    Default Re: Sunbeam 1949 S8

    Thanks for this....more to look into....the forks at 45 appear to vibrate/flap front to rear, a little like the washboard analogy. Fork oil/springs/tyre roundness bead etc are all candidates too!

    The red charge light is intermittent it stays on sometimes whilst revving, then appears to go out if you give it a handfull or, blip the throttle and it sometimes sorts it out. whilst riding the bike has developed a miss fire when you wind it on....it bogs and misses (electrically) then if you back off it goes back onto two. Its not wet anymore, I thought it coincided with the rain but I shall investigate the points () everyone's raised. It was a big shakedown 70 miles (thats what my bum told me!)but I think on balance its a good bike, its just got a little electrical niggle ATM.

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    Default Re: Sunbeam 1949 S8

    The full throttle miss could be many things. Replace the plugs and clean and gap the points. could be a crack in HT insulation or distributor cap or somesuch, damp inside distributor cap (WD40 was invented for that), bad spark plug. Plug caps that seal to the plug with rubber tend to trap dampness. Sometimes ignition coils just get old. Any coil from a 6V points system should work. A flat battery is more likely to miss at high rpm than at wide throttle, but who knows really?

    If there's an ammeter on the bike, it should show a discharge when idling with headlight on. Rev up and the needle should rise to zero or go into positive charge. As the battery charges up, the positive reading will fall back to zero.

    Dave's out of round tyre or wheel theory would fit that front to back thing (but who knows really?).

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    Default Re: Sunbeam 1949 S8

    Quote Originally Posted by ink ink View Post
    The full throttle miss could be many things. Replace the plugs and clean and gap the points. could be a crack in HT insulation or distributor cap or somesuch, damp inside distributor cap (WD40 was invented for that), bad spark plug. Plug caps that seal to the plug with rubber tend to trap dampness. Sometimes ignition coils just get old. Any coil from a 6V points system should work. A flat battery is more likely to miss at high rpm than at wide throttle, but who knows really?

    If there's an ammeter on the bike, it should show a discharge when idling with headlight on. Rev up and the needle should rise to zero or go into positive charge. As the battery charges up, the positive reading will fall back to zero.

    Dave's out of round tyre or wheel theory would fit that front to back thing (but who knows really?).
    The charging seems normal and the ammeter bears this out. The miss fire is as you say one of the above and is familiar territory....though, not recently! There was a definite start to it rather than a gradual thing. (when the rain started) There may well be a bit of lurking moisture ......or there may not!!

    Its nice that all the old bike/car electric ailments are written up here, we all think we know them but its easy to forget one or more and miss the one that's the real culprit!

    Wheel wobble/tyre roundness at a "resonant" speed seems favorite at the moment but again half the fun's fettling stuff.

    Cheers all.

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    Default Re: Sunbeam 1949 S8

    this is a bike?

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    Default Re: Sunbeam 1949 S8

    Quote Originally Posted by taou View Post
    this is a bike?
    Welcome to TRC, and yes, you'll learn ,maybe

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    Default Re: Sunbeam 1949 S8

    Whats the latest Rodbargee? Any more fettling?

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    Default Re: Sunbeam 1949 S8

    Not a lot of fettling to report really, works getting in the way of lazy Sunday spannering. The battery is a bit suspect lately and is due I reckon to the previous owner who wired up "retro indicators" to be permanently live, along with the horn. Its been a long time but I am reasured that's how bikes of that vintage were wired ...with the horn live at all times. Horn I can perhaps see but the indicators I think should be only active with the ignition?..... at the moment if you listen carefully you can hear flasher unit at standstill "pinging" I think that's (sure) draining the few volts that are on offer plus the battery is as old as LJK Setright too, so all combined starting has become an issue so new batt on the way....and a looksee in the headlight.

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    Default

    Great thread.

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    Default Re: Sunbeam 1949 S8

    The horn is generally as you say permanently live from the battery (doesn't go through the ammeter) and the horn push completes the circuit by earthing the return feed. It shouldn't cause a drain.

    Why not check by disconnecting the battery live then connecting an ammeter between the battery live and the lead. That will show you whether you have a drain and by progressively disconnecting things you can find out where.

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    Default Re: Sunbeam 1949 S8

    6 volt AGM batteries and old style cases from here.
    He also does halogen and led replacement bulbs that can help with the load.

    Motorcycle batteries

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    Default Re: Sunbeam 1949 S8

    A permanent live indicator system sounds silly to me, but the live horn isn't all that bad an idea. The simplest way to wire a horn was Battery live, horn in, horn out, handlebar, earth return to battery. Also a horn was liable to blow the fuse, so wasn't on a fused circuit.

    It was common to have the brake light on a permanent live on old bikes too, but with switch in the live feed, probably just because the battery and the brake light switch were close together.

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    Default Re: Sunbeam 1949 S8

    *Thread resurrection*

    I am just about to take on a Sunbeam S7 Deluxe from my Dad. He bought it in 1962 and restored it. But has been left covered in the garage for many years!!
    Will Post a fresh thread when I get it to my work shop. But in the mean time have found this:

    Bonhams 1793 : 1951 Sunbeam 487cc S7 De Luxe Frame no. S7 5479 Engine no. S8 8073

    Which sold at Goodwood this year!!!

    To say I am looking forward to getting it is an understatement!!!

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