Speedo reading fast

[gdwales]

Just bought a 1979 BMW R100RT, thought it was deceptively fast till I put my Satnav on it.
Found it is readind 10mph fast at indicated 45 MPH and 14 MPH fast at indicated 70 MPH, anyone got any ideas, have not got round to getting a manual for it yet, I am sure everything is standard or original except the new Continental tyres I just put on...........HELP
Peter


Oops, should this be in "Toolbox" section?

[Rambler]

Hmmm
well, as it is a fair few years old, there is a chance the gearing driving the speedo is a touch worn .........
maybe have it checked over at a garage
just be thankful it aint reading UNDER
cos the boys in blue would just love that excuse

[Welsh Wizard]

most speedo readings have some flatter in them though thats seem to be be a bit high at 10mph, normal to be about 5mph.