1954GF speedo drive

[victortrry]

What is going to happen when I replace the sidecar rear sprocket with a solo sprocket.
Do I also need to replace the speedo drive in the gearbox?

Victor

[bsa-bill]

No
But it a good point that's ignored by most (shouldn't have said that)
I assume BSA made them as singles so are geared as singles and a sidecar would be an addition by the owner who would change the sprocket, I've never seen or heard of a sidecar speedo (but I'm no wikipedea)

[duTch]

 Vic, It'd be easy for me to say something along the lines of ' how'd you get a sprocket on the sidecar. ?' but I won't.......
   So what exactly are you doing....? Are you removing the sidecar and going solo..as the wording otherwise suggests.?
   If so you shouldn't need to do anything as if you replace with a standard gearing sprocket, the speedo should be calibrated accordingly.
  If adding a sidecar, then you'll just need to do some mathematics and note the difference in ratios and calculate the speed (also) accordingly..!
 In this case, you could do what I did and add a bicycle speedo and calibrate it however you want...!

[Brian]

Here you go Bill, a listing of speedo's including the correct ones for sidecar use.

[Greybeard]

I wanted to check my speedo for accuracy. I found a free App for my mobile, (7" tablet) device that shows speed using GPS location. I've read that this is an accurate system, but only on flat ground; the system cannot calculate gradients. I bungied the tablet to the top of the petrol tank and went for a ride. I discovered that my BSA speedo is more accurate than my modern car which over reads about 10%.

[bsa-bill]

Nice one Brian

Sometimes you just know when your typing there's a doubt

Lots of us making for the shed at this moment to check

[muskrat]

Speedo's always seem to read fast. I thought I was Doing 180KPH but the speeding ticket only said 169 .
Get a mate in a modern car to sit on 60, follow him in 4th and note your reading.
Cheers

[bsa-bill]

I thought I was Doing 180KPH but the speeding ticket only said 169

 

[duTch]

   

Get a mate in a modern car to sit on 60, follow him in 4th and note your reading.

 ..but....?
...

Speedo's always seem to read fast.

  ?


   

[trevinoz]

Victor,
            With a bit of luck the speedo ratio will be printed on the face. Solo should be 1450, or thereabouts.

Trev.

[wilko]

If your speedo reads fast take a weight or two off your balancer wheel in your speedos guts. If It's slow add some weights.

[victortrry]

Dutch
 I am changing from 49 .tooth sprocket to a solo 42 tooth.

Victor

[duTch]

 Thanks Vic- that's what I have(standard), sometimes feels like it could use a bit longer legs, but only possible with bigger G/box sprocket, but that may be a bit too much.?

 My speedo is not the right one, is a 3305/22 - 1620, and reads about 10%slow (~89 instead of 100). As Trev (I think) said you need a 1450? 1490 rings a bell too, but someone who has the right one will know.
 Tyre profile/rim dia. will also make a difference, you'll just need to do a rolling diameter(circumference) check, and some mathematics if yer keen enough