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by Mal Marsden - 06/16/22 7:00 pm
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Allan G, The Bonneville Shop
Total Likes: 6
Original Post (Thread Starter)
by S-NJ-W
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.

[Linked Image from]

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

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

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

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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,

Liked Replies
by bon
Its a pity they cannot go the extra mile and get them spot on in terms of dimensions.
1 member likes this
by Stuart
Hi David,
Originally Posted by DavidP
I presume that they come calibrated for an 18" rear wheel.
calibration screw accessible from the outside of the gauge for those of us with 19" rear wheels?
confused 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?

1 member likes this
by raf940
here's how i did mine on my 72 OIF Bone-vile using 1960s era instrument plate and headlite ears.
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1 member likes this
by Stuart
Hi David,
Originally Posted by Allan G
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.
+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 ...


1 member likes this
by S-NJ-W
Originally Posted by The Bonneville Shop
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, t'was yourself that supplied the clocks. Thank you for the astonishingly fast shipping!
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