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

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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
 
The gear box is either a 2:1 or a 4:1 ratio , you will need a corresponding rev counter to match.

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).
 
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.
 
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.
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.
 
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
 
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?view=detailV2&id=590026BA31E2BEA89C2B01F519F10D22CA82866F&thid=OIP.U7jLk-Gwi1x1fuiKkLckJwHaFj&mediaurl=https://eglivincent.files.wordpress.com/2013/12/10.jpg&exph=857&expw=1143&q=BSA+500+gold++star&selectedindex=16&ajaxhist=0&vt=0&eim=1,2,6

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
 
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.

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
 
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.
 
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.

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
 
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