Speedo for a Superflash

[MikPowl]

Does anyone know what should be the correct spec. for the Smiths speedo for a Superflash?  The item I have from the bike is an S.433 /3/ L.   From the records I can find this would be correct for an early Goldie - would it be right for the SF?

[KiwiGF]

Does anyone know what should be the correct spec. for the Smiths speedo for a Superflash?  The item I have from the bike is an S.433 /3/ L.   From the records I can find this would be correct for an early Goldie - would it be right for the SF?

An often asked question, first thing would be to establish if the number on the dial still represents the actual spec of the speedo eg revs per mile, trip location, bezel type etc etc

The good news is a skilled instrument tech can quite easily adjust the internals to what is needed for a particular bike, and most likely add/subtract all the other features needed as well, possibly printing the correct dial as well.

[MikPowl]

Thanks for that. As far as location and purpose I guess the SF speedo would be identical to an early Goldie - certainly uses the same mounts and series gearbox. What is the meaning of the codes? I remember finding something about these years ago but now no amount of Googling cme up with what s.433/3/l actually means!

[KiwiGF]

Thanks for that. As far as location and purpose I guess the SF speedo would be identical to an early Goldie - certainly uses the same mounts and series gearbox. What is the meaning of the codes? I remember finding something about these years ago but now no amount of Googling cme up with what s.433/3/l actually means!

I am unaware of any way to interpret a smiths part number/code but maybe this will help?

https://www.a7a10.net/forum/index.php?action=dlattach;topic=630.0;attach=1225;image

[Slymo]

Here is a useful archive site for Smiths Instruments. A bit of searching required but quite fascinating

http://reocarchive.byethost31.com/Smiths/smiths.html?i=1

[MikPowl]

Many thanks!  That's really helpful. It doesn't cover the SuperFlash but id does mention the '54 Road Rocket which had the same instrument layout. Also, looking at the parts books all the early A10's shared the same wheelsize, a 42tooth chainwheel and the same speedometer drive gear part which suggests that they all, plunger or SAF, had the same 'turns-per-mile' internal setting for the speedo. So, if I go for the '54 Road Rocket all should be well!  Thanks again.

[limeyrob]

Don't want to mention the obvious, but don't forget the speedo is off the gearbox so it has to match the final drive sprockets so a Flash is unlikely to have the same speedo as a Goldie.  I've no doubt back in the day no one cared, I used to swap the gearbox drive sprocket when I took the chair off and never gave the speedo accuracy a thought.
I drive an old Land Rover and these have the same problem - speedo off gearbox but a range of rear diff ratios and wheel sizes.  We all live with speedos that are out by at least 10%.  I supect you will have the same problem we have with the Land rovers, the speedo ratio we most need seems to be the least made