Speedo calibration advice needed

I need to recalibrate my speedo as it reads 70mph when others show more like 60mph. I took it off and see there is already a hole drilled to access the adjustment screw. How many turns should it require and would that be c/w or anti c/w when viewed from the back? thanks.

Take the speedo off the bike and mount it on a stand of some sort which gives you access to viewing the dial face and adjustment screw. With a short length of speedo cable inner with the squared end in the speedo and the other in a variable reversible speed drill. Operate the drill in the right direction and increase revs until you see 70mph on the dial, move the adjustment screw until you see 60 mph with the drill at the same revs.

Dedubyah said:

70mph when others show more like 60mph.

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If you’re not sure how big the discrepancy is, get a speedo app on your phone and tape it to the handlebars.

Dedubyah said:

I need to recalibrate my speedo as it reads 70mph when others show more like 60mph. I took it off and see there is already a hole drilled to access the adjustment screw. How many turns should it require and would that be c/w or anti c/w when viewed from the back? thanks.

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Is this adjustment hole drilled at the factory or something an owner needs to do? Could someone post a picture or explain where it is? Thank you!

Jonez69 said:

Is this adjustment hole drilled at the factory or something an owner needs to do?

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No, you have to do it as Smiths never added a hole for access.


The problem with drilling the hole without dismantling the speedometer is loose swarf and where it could end up.

I did mine successfully by rigging up a bicycle speedo display with magnetic pick up off the rear wheel...calibrated according to wheel tyre diameter as per instructions. With bike up on CS, wheel well clear if ground...run the engine and with 1st gear engaged, watcged to two speed displays and made small adjustments on the smiths until they matched well. Took out on higher speed runs on road and made a few fine adjustments. Done. Confirmed with a gps displayed speed on my phone while riding.

Edit: all adjustments made with smiths mounted on bike, carried a small screw driver and able to tweak the screw as needed btwn runs.

Jonez69 said:

Is this adjustment hole drilled at the factory or something an owner needs to do? Could someone post a picture or explain where it is? Thank you!

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Ascper older threads on this topic, the brass slot head screw should be barely visible through the lamp hole of the casing. That will let you know where to make the hole. Use caution not to drill fast/hard through casing so as not to punch through into the screw below and reduce swarf. Maybe use grease on the bit to help hold swarf. I dont recall taking much precautions and never had any issues...more the 8 yrs since doing this amd some 22k miles.