I just bought a speedo cable for my new-on-the-road B25.
It is reading double the actual speed. ie 120 mph at 60.
Does that mean its the wrong speedo?
The rear wheel speedo drive is the normal 2;1
Mick
Assuming it's a genuine Smiths speedometer, what is the refence number on the face? Should begin with SSM.
Paul.
If it's a 1600 revs speedo and 18" wheel & 3.5" tyre then a 2:1 drive is right.
I am wondering if the calibration can be this wildly out
e.g. I note that the C15 and B40 speedos are both 1600 revs units and the wheelsize difference is addressed by different drives. yet the c15 unit has a 80mph max and the B40 a 100mph max. The only things in the speedo itself that could allow for the difference would seem to be the magnet strength, the calibration adjustment via an amplifier plate that varies the magnetic field strength on the drag disc, or the strength of the coil spring. ( I had no answer on this forum as to what makes the difference )
What's the max speed on the dial...120mph ? and what the SSM number ?
Depending on the B25 model/year Rupert Ratio says the speedo should be:
67-69-SSM5001/03 grey face 80mm 120mph max
70 SSM5007/02 grey face 80mm 120mph max
71-72 SSM2001/07 black face 60mm 120mph max
Mick, knowing how you like to ride, I'd leave it as it is!
I tried a new speedo from ebay. £17.50.
It did not have the normal square hole for the cable.
Refitted the original, quick test in the workshop - readings now seem more reasonable.
Perhaps the speedo has got a bit out of sorts after a 40 year lay-off!
Mick