A10 speedo drive ratio

[Pete A10]

I'm rebuilding an A10 Golden Flash and cannot work out what is the correct speedo. Engine is from a 1955 bike. The rebuild is a complete bitsa so originality is not a problem. The speedo is driven from the standard gearbox drive and all gear ratios are standard. I have seen various repro chronometric speedos for sale (I know the quality will not be brilliant) however I am confused regarding the drive ratio. Some are shown as 2:1 and some are 15:12. Anybody know which is correct and may provide somewhere near the correct speed reading.

[TTJOHN]

I suggest yo get in touch with Chronometric Services Ltd, they will tell you, they are very helpful, I believe the ratio is 2/1, not sure but that seems to stick in my memory, if you  buy a cheap repro you will have to use one of their drive cables, normal ones won't fit.

Regards TTJohn

[JulianS]

The original Smiths speedos were not listed in a drive ratio but on rear wheel revs per mile (EG 1440 on speedo face) . On the A10 another variabl is gearbox and rear wheel sprocket size. So it is difficut to know which of the repro speedos to use and how accurate they may be.

Ratios are given for rear wheel drive speedo gearboxes but the speedos are still listed by rear wheel revs per mile.

You could ask the supplier?

Drive ratios were given for rev counters only by Smiths.

[Pete A10]

Thanks John and Julian.
I've managed to identify the correct speedo as a Smiths SC3305/04 1440. Even found a refurbished one on ebay but its £350!!! That's about a quarter of my budget for the whole rebuild hence the search for a repro.
I've spoken to one supplier of a 2:1, 120mph repro but the answer I got was that it was up to me to decide if it would fit or not - bit of a disappointing reaction.
Feels a bit cheeky to ask a quality outfit like Chronometric Services about a cheap Indian repro, but maybe I'll have to - or maybe I'll gamble £22 and see if it works checked against a sat-nav.
Thanks for the tip re cables - I think the repros have a larger thread.

[TTJOHN]

Pete.

I had a speedo refurbished by Chronometric services Ltd and it came back like new but I know that they have some on the shelf for sale for about £200 I think, so I would check with them first before getting a cheap Indian one, that is if you want a good one.

Regards TTJohn

[Pete A10]

Thanks John
Even at £200 its a bit too much - I'd rather put the money into the engine or the running gear. Like I said its not meant to be an original rebuild - its one of those ones that develops as you go along - its heading towards being a classic bitsa café racer as you would have had in the 1960/1970's - maybe not one for the purists but hopefully it will look and go well. Think I'll risk the repro and hope there are no speed cameras operating when I take it out.

[PAUL WILSON]

Another thing to look out for in replicas is the position of the drive on the speedo - they are all in the centre not offset as original - I bought one for my 1958 GF to find I can have the headlamp in or the speedo cable connected - but not both !
Still waiting to find a reasonably priced original or replica with offset drive - it either exist !