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what is involved adding a tach drive to a '61 ES2 500 single?

Discussion in 'Other Norton Motorcycles' started by JamesWeyand, Aug 14, 2019.

  1. JamesWeyand

    JamesWeyand

    Joined:
    Aug 10, 2019
    What is the process for adding a tachometer drive to a 1961 Norton ES2 500 single? I'm thoroughly confused with all the different drive ratio information out there and need help from the experts on what's right for my engine.

    I just posted a wanted ad for a timing cover with tach drive already installed but if I can't find one for sale, does anyone know a member or good machine shop that can perform this modification on an ES2 and install a functional tach drive?

    Jim in Seattle
     
  2. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
  3. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Camshaft driven tach drive gearboxes are generally 1:1 ratio (either reversing or non-reversing) to suit 2:1 rev counters (Atlas, SS) or 2:1 (rev./non-rev.) to suit 4:1 revcounters (20M3 Commando).
     
  4. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
  5. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Might it be easier to consider and electronic tacho?

    If it’s coil ign you could used an original looking smiths job.

    If it’s magneto that won’t be possible but you could use something like a Scitsu.
     
    jan nelder and johnm like this.
  6. ntst8

    ntst8 VIP MEMBER

    Joined:
    Feb 14, 2004
    My thoughts too. Featherbed singles were coil ignition from new so should be simple, and the smiths chrono replicas have the step function on the needle movement so look original.
     
    jan nelder likes this.
  7. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Re; “If it’s magneto that won’t be possible but you could use something like a Scitsu.”

    Tut..Tut – it’s not a timing cover you need, as the mag is already reduced to 4:1-what u need is a 1:1 rev counter drive, like on the BSA in pictures, fit a big nut with suitable slot on end of magneto, fit clay/plasticine into top of timing cover push on and then drill in the centre a pilot hole followed by a bigger hole and drill the two holes for the bolts, welding two nuts on the inside.

    The 500 Gold Star shows how its done;


    http://onlymotorbikes.com/public/16/bsa-500-ss-gold-star-1972-moto.jpeg

    https://www.bing.com/images/search?...ar&selectedindex=16&ajaxhist=0&vt=0&eim=1,2,6
     
  8. marinatlas

    marinatlas

    Joined:
    Nov 4, 2007
  9. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
  10. desmo

    desmo

    Joined:
    Aug 16, 2019
    you need to establish the centre of the shaft in relation to the timing cover
    assemble the cover with a blob of modeling clay ,then remove and measure thickness , remove nut on mag drive and get someone to turn you up a
    pointed nut a couple of mm longer than
    than original nut + thickness of modeling clay fit piked nut assemble case and ding the aproximate area with a mallet this will transfer the centre of shaft via the nut /centre punch !, drill a hole a small pilot one for now as a reference to aid marking out
    now you may have to build up a bit of a platform by marking out the base of your drive unit and build up the area by tig welding ,or i suppose you could use jb epoxy if youre a cheapskate.
    now drill a clearance hole for the spindle and spigot of drive ,spot drill thru the unit f
    or mounting holes ,and drill thru and tap
    get a forked drive nut ,3/8 bsf for mag end goldstar? or if using bottom sprocket 3/8 bscy inter /manx ?
    or make one
    check that the spade end is not bottoming in the fork when fitted again plasticene /blutack will establish this

    well thats tin shed engineering for ya
     
  11. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Do you have an advance /retard unit on the end of your mag/distributor?
     
  12. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    Not so. There are HT sensors which read the change in magnetic field around the HT wire. Here is an example:
    https://shop.revivalcycles.com/motogadget-ignition-signal-sensor/

    I have seen another one in the list of accessories for Smiths electronic tachos as well.
    No mechanical interaction needed, and a lot cheaper to realize.

    -Knut
     
  13. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    That’s what a Scitsu tacho does Knut, it simply has a wire that is taped to the HT lead.

    The lead you show is for a motogadget.

    If there’s a known way to make a Smiths work with a mag that’s great, please share if you know.
     
    desmo likes this.
  14. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    Thanks for the clarification, Eddie.

    For a suitable sender to drive the Smiths electronic tacho off the HT lead, look here:
    http://www.puca.co/accessories.html

    -Knut
     
  15. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Thanks Knut, yup that’s clear, they’ll work perfectly with a mag!
     

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