Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Fitting EMGO speedo/tach to OIF cups

I mentioned some time ago that I was in the process of trying to work out if I should re-furb my existing Smiths speedo and tach, which are pretty beat up and faded, or buy new EMGOs.

To have the Smiths clocks re-furbed was $225 each.
To buy new EMGOs was $65 each.
The web sites selling the EMGOs made it clear that the EMGOs were 1/4" deeper than the Smiths and were not just a drop in replacement.



Fitting the EMGO clocks to the OIF cups only needed the two rubber 'nubs' in the cups to be removed with a craft knife.



The clock then just pushed into the rubber cup and the top edge of the cup sealed around the bezel.



The speedo needed a hole cut into the cup for the tripometer reset, but the cup is profiled at the right point.



Nothing to fear, apart from stabbing yourself with the craft knife. Don't do that.

I am going to make up some 3/16" alloy spacers so the the clocks can be 'bolted' to the cups without crushing the rubber,

Steve.

excellent x-planation i used a dry frame triumph mounting plate on mine sans the cups either way is good

I've been using the grey-faced replica speedo's on my 68 B44 and A65 for quite a few years and find them to be excellent.

The grey-faced version is taller than the black face type and needs a lot more material removing from the binnacle and only just fits after removing a lot of material from the binnacle base.

I've also used black-faced replica speedo & tacho on my Norton Commando which required modification to the alloy mounting cups to get them to fit.

Given the price and reliability of the replicas, I don't think I would consider having an original Smiths clock rebuilt, unless it was for a Concours restoration.

i have the emgo ones in all my bikes they are smooth and accurate and all have several thousand miles trouble free.......... but that's just me

100% Agree Gunner. Personally, I prefer the pre '71 instrument binnacle.
In the end the difference in cost of $500 (inc shipping) for the Smiths vs the $130 for the EMGO clocks was hard to ignore.

Its a pity they cannot go the extra mile and get them spot on in terms of dimensions.

They are cheap and reliable as they are based on a Japanese clock, change the dimensions and cheap bit disappears with tooling costs for a deep drawn die and bolster.

I presume that they come calibrated for an 18" rear wheel. Was Emgo nice enough to make the calibration screw accessible from the outside of the gauge for those of us with 19" rear wheels?

There’s probably half an inch between the OD of a 400:18 and a 3.50:19

If it’s a unit single with 3.50:18 these will have a different speedo and gearbox anyway.

Hi David,
With respect, surely you know by now the diameter of the wheel rim makes only a limited difference to the diameter of the complete wheel with tyre?

You're talking about an (A65?) 18" rear wheel with a 4.00 tyre and a triple's 19" rear wheel with a 4.10 tyre. There's absolutely bugger-all difference in overall diameters; what use would a "calibration screw accessible from the outside of the gauge" be?

Regards,

After about 10 years of being built, my once really accurate smiths Speedo now reads 10% slow at at least 40mph. Not been through any other speed traps to check other speeds 😅

No calibration screw, as its for a 1.25:1 rear speedo gearbox it will be equivalent to the Smiths 1000 markings ie rear wheel turns 800 times per mile.

Hi Allan,
Just a thought but possibly telling you it needs a service? Also, iirc the distance between magnet and needle can be altered when the speedo. is open?

Hth.

Regards,

That or the speed trap is out of calibration. I'll try it against my GPs this weekend. I aught to make a rig that I can check them on.

Im thinking a rheostat connected to a DC motor, then driven speed of the gearing checked with a digital tachometer.

Excellent idea, S-NJ-W. We sell a lot of the reproduction instruments and will remember this modification for the oil-in-frame motorcycles using the soft rubber binnacles.

Dave

here's how i did mine on my 72 OIF Bone-vile using 1960s era instrument plate and headlite ears.

Dave, t'was yourself that supplied the clocks. Thank you for the astonishingly fast shipping!

So, if you have a larger rear wheel you're stuck with whatever the gauge reads. Can I say bollocks without it being stricken?

Yes but the most you’ll probably be different by is 5mph from a low profile tyre fitted on either rim. If your comparing a 3.50:19 against a 4.00:18, likelihood is they will read the same as the overall tyre size is the same.

Too add more confusion to the latter. I had a speedo reading change when I took off my Emgo speedo gearbox and fitted the LF Harris one. They should both be identical 15:12 gearboxes.

Smiths did nothing for the 1000 turn speedos, but for the 1600 they did 2 rear wheel gearbox ratios, 21/10 and 2/1.

Hi David,
+1. A 4.10 is "low profile" because its section width is greater than its section height, whereas a 3.50's are the same, and only section height has an effect on overall diameter. The idea was 4.10 replaced 3.50 (do TT100's still have "REPLACES 3.50" moulded on them?). 4.00x18 and 4.10x19 are pretty-much the same overall diameter, certainly the Dunlop overall diameters for 4.10x19 TT100 and 3.50x19 K70 are within 1/4" ... on that basis, you'd be recalibrating the speedo for tyre wear ...

Hth.

Regards,

As an interesting aside, I put an Emgo speedo on my '69 T100 but with the 2:1 gearbox. The difference is 62.5% while a km is 62% of a mile. My speedo now reads in km/hr!!! Close enough to keep me out of trouble in Canada.
Tom