Hitchcocks Forum

Hi friends
Been a while since I was in here so maybe this topic already has been discussed. Anyhow; my speedo is showing wrong spped. It's in kmh and the fault is about 20 kmh to much at the speedo. The speedo drive is 2:1 and the scale is 0-160 kmh. It's a Smiths replica.

What can be wrong? I have tryed 2 different ones with the same result. If there is no fix to it maybe some of you know where to get a better one? Must be kmh, old style like Smiths and preferably white face.

They're just cheap magnetic instruments with a replica (sort of) Smiths dial and quality can vary. If you have someone near to you who can repair magnetic instruments you might be able to get them calibrated properly, otherwise you have three options, for which You Will Need To Get Your Wallet Out!



1. Get an original genuine Smiths chronometric speedometer, perhaps an old one needing repair. When it is being rebuilt, whoever is rebuilding it will need to know what ratio speedometer drive you're using (normally 2:1 on an Indian Bullet) and the circumference of the tyre on whichever wheel drives your speedometer (usually the front one on more recent Indian Bullets).



2. Get a digital chronometric from Puca-Smiths, an offshoot of the original company, available in kph as well as mph, and with an electronic trigger to fit the old speedometer drive. Full calibration instructions are given if you want to set it up manually, as well as pre-sets if you have a standard 19 inch front wheel.



http://www.puca.co/productC.html



3. Get a GPS speedometer, there are some classic-looking instruments about which ALMOST fit the existing speedometer hole in the casquette, I think you have to enlarge it by 5mm. Might not work in Tunnels or in case of extreme solar flares! For example:



https://www.ebay.co.uk/itm/12-24V-85mm- ... SwTEZcIeOF



Hope this helps.



A.

Hi Adrian

Thank's for your answer. Will look around for a solution. Most likely try to calibrate one already in my garage. Or try one from our host. I guess they sell better quality than Ebay.

There is a similar problem further down the page.
Things to check;

are the tyres and sprockets standard size as they would have left the factory?

Leon,



the sprocket size is irrelevant, the speeodmeter drive is either taken off the rear wheel, Redditch and early Indian Bullets, or the front wheel on more recent Bullets.



Most tyre munafacturers will post on an on-line data sheet on their web sites, so that you can calculate the tyre circumference if you don't want to get the tape measure out.



A.

Or get one of the replica Smiths style speedos our hosts list - there are over 12 different versions and as far as I know they are checked for calibration and guaranteed.

http://accessories.hitchcocksmotorcycle ... peedometer

My speedo is now as accurate as can be. It was reading a consistent 12 MPH fast. Other than removing the bezel and glass, the rest is easy. I simply pulled off the needle and replaced it CCW the same number of degrees it was reading higher than than it should.  I simply bent it up slightly to settle above the stop peg. Testing was a simple ride with the glass off, stopping to fine-tune the needle angle until it matched my bicycle speedometer at different speeds. Easy peasy. No need to even remove the speedo face or housing. I rode home to remove the speedo, crimp on the bezel and Bob's now my uncle.

Felix said "My speedo is now as accurate as can be. It was reading a consistent 12 MPH fast."



Felix, does that mean it was reading 12mph while you were stationary? And 32mph when you were really only doing 20mph?

Mine reads about 12mph high at a real speed of 60mph, but only 6mph high at 30mph. I think if I did as you described the lower speeds would read too low.

Aethelric,
Mea culpa. I wasn't clear. At my cruising speed of 60 mph my speedo reads 60 mph. My needle rests against the peg at 0 mph and rises to 30 mph at 30 mph. Those two speeds were matched by a roadside radar sign on my usual route, as well as a Sigma bicycle speedometer calibrated to my tire circumference. I didn't check other speeds since I was happy with the result. Compared to adjusting the springs that restrain the needle against the magnet/cup assembly this is an easier way to modify a cheaply made speedo.
No longer cruising at 60 mph and reading 72 mph.