Speedo reading

[Craigy]

Swarthy,

I suspect non original. The bike was a box of bits for 50 years.

I also have a ‘59 with smiths clock and ‘s’ model number

[chaterlea25]

Hi Craig,
That's a copy made in India,
Pot luck with the ratios inside
If you want an original chronometric it will be expensive 
Buy a correct ratio one from a specialist rather than pot luck on eBay or such which will cost as much again to sort out..
OR, buy a GPS cycle computer

John

[Swarfcut]

 All is revealed. As CJ says it's an Indian version of a look alike, and side by side the difference is like night and day.  Swap them over for a statutory test in the short term, but don't waste time with the copy...they're only good for blocking up the hole.

 Smiths are still going, with vehicle components made by a close associate company in Swansea, South Wales. They make new speedos, gauges etc for the upmarket classic car market....and Henry Cole's Gladstone outfit and a curious Czech inspired retro electric scooter. All on their website if you can be arsed to look them up.

 Swarfy

[groily]

That's an Indian jobbie, yup.
IKBA about speedos and their zillion versions and I have never dared take a chrono completely to bits, but a typical Smiths 150 job looks like this pic, which I'm pretty sure is original to the '66 650SS it's on. Probably made them with '0mph' positioned like your earlier 125mph one too, dunno. The only other Smiths 150s I've seen apart from on bikes like mine have been the big ones on Vincents. All I know is they all cost a lot of beer vouchers to obtain, or to have overhauled properly by an horologist-type person. (My matching tacho started as a speedo and had ££££ invested to create something that is to all intents and purposes correct.)

You mention your older one is fluttery over 60mph. I have one which has been fluttery over 55mph since 1976, but still works. Opened it up to see if there was anything obvious - there wasn't (as if I knew what I was looking for!) - but someone had been in there before me and written 'Sticky Movement!' on a bit of glued-on paper. I give it a drop of Singer sewing machine oil for the want of anything better now and then, and it hasn't changed in a good couple of hundred thousand miles. It's a NOI ('next owner issue') - probably for my daughter  . . .

[chaterlea25]

Hi All,
In a chronometric Speedo,the speed and mileage recorder are two separate mechanisms.
I have had the speed mechanism' s apart and repaired a couple of my own. The speed can be adjusted to some degree if you have spare weights The "balance" wheel comes in different weights plus clip on widgits for fine adjustment..
I have not attempted to work on the mileometer except to repair the ratchet pusher.. as far as I could figure out the ratchet wheel comes in different tooth numbers to calibrate? Or has the eccentric a different stroke? Having seen a damaged set of number wheels apart I figured it best not to go there
This was all more than 15 years ago when my eyesight was a lot better 
I will need two rev counters  for my projects , a  3:1  for the RGS and a 4:1 with 2:1 face for the Goldie project
BSA Gold Stars, use a 2:1 rev counter but they wear out at an expensive rate due to the high speed that the internals have to endure. I found a 2:1 drive box that halves the cable and internal mechanism speeds.
Then the 150mph Speedo for the RGS will need reconditioning too
I have a good Speedo for the GS project though 
I think I has better buy some lotto tickets

John

[Rex]

For the unwary, there's a very easy way to tell a Chrono from a Taiwan, namely as the Taiwan is a magnetic speedo the cable entry at the rear is central to the casing, while the Chrono enters off-set from the centre. This can cause problems when the speedo is mounted in the tank or headlamp shell.
The Taiwan repro's also usually have a green plastic ring visible between the glass and the face.
As said, OK for filling a hole but not much good as an accurate speed indicator.

[Craigy]

Thanks very much guys, I have learnt something here.

1/ It’s going to cost
2/ Don’t touch it.

I’m new to classic bike ownership so have lots to learn.

John, I was thinking about mileage recording v speed and wondering if they were connected as the miles seems to be going up too quickly as well. I’d assumed that they must be connected. If I ride for an hour at what the speedo says is 70mph, I’d guess the mileage will go up by 70 miles. It’s interesting that you say they are not connected and probably too much for my pea brain, but not sure how that works.

As far as original Smiths clocks go, is there as ‘off the shelf’ correct model for a ‘52 A10 (s…..) or do I. We’d additional info to source from a variety of option?

Thanks for all your help. Very much appreciated.

Craig

[limeyrob]

A chronometric has two mechanisms, a mileage recording one and a clock one that calculates speed.  They are driven by the same cable and at the same speed.  If the mileage is being driven too fast then the speed calculation will also be too fast.  Get the mileage right and you will get the speed right (or close).  Are you sure you have the correct speedo?  How far out is it.  What drive sprocket do you have on the gearbox?

[JulianS]

Below factory service bulletin from 1955 gives speedo face numbers.

[Craigy]

Below factory service bulletin from 1955 gives speedo face numbers.

Thanks for that Julian, great info.

Bike is a ‘52 A10 GF Plunger, so guessing #546/3/L is the correct one in mph

[Beeza]

Hi Craigy, you have the plunger model with the (cow pat/divers bell) nacelle, you are in luck as there is quite a few crono speedos of varying face numbers to suit you for that bike, it is everything from early A7/10 & some B models to the last of the swing arm A7/10 and B32/34 even gold stars, the main difference is final drive (gear box sprocket/wheel sprocket), hope this doesn’t razzle you too much, but they are available.
What you do need is a unit that has the trip reset poking out through the bottom of the casing, then there is a long plastic extension that gets connected to that via a split pin ( more on that later).
The chrome bezel for the cow pat nacelle is unique in that it has a small protruding lip, this sits in a unique rubber speedo mount grommet, to get this speedo into the rubber and then into the cow pat nacelle without cursing all of the BSA design team is NOT possible.
So some good points, and some challenges.
I do have a great chronometric guy in NSW that will work with you on whatever you can come up with, I may even have a correct bezel, just gotta look for it.
Thomas.

[Craigy]

Hi Beeza,

Great info, cheers.

I think I have my head around the final drive/sprocket. So if the speedo is not the one listed but from another model, the speedo drive is different, meaning the sprocket needs to be changed to marry up with the speedo. Is that right?

There is a referb one on eBay in US. $1,000…..OOPH

I’d happily speak with your man if needed. Cheers

[limeyrob]

No! the final drive sprocket is sized to match the engine and use, so a tuned engine for road use has a larger sprocket, a std engine with a sidecar has a smaller sprocket.  The speedo drive gears are fixed so you the match the speedo to the final drive.

[jhg1958]

Can you not get a gps speedometer for the A10?  It seems an ideal solution given that the speedo changes with chain sprocket sizes, tyre size etc.

Not so good if you want an original spec but could be very practical. Might save all the oil leaks from the cable entering the gearbox.

John

[Beeza]

This is my 57 flash speedo , I believe the 1450 is the calibration, S608/11 is listed for a few models. This is the correct rubber grommet mount to suit the divers bell nacelle.
The Speedo configuration you should have is the one on the right, with a small flange on the bezel, and the trip meter reset poking out the bottom, the one on the left suits a face mount or bracket mount.
Thomas