3TA's and 5TA's had these,did'nt know about the 250,but they where totally useless,to see them you'd have to lift your right leg,lean out to the right,take about 10 seconds to see what gear you're in then swerve to avoid the approaching tram,bus,lorry etc...By the way,which Velocette did you have,I had a Velocette Valient,I think it was in 73,a little boxer twin
