My 2006 K1200R read an indicated 103kph when the GPS showed 100.  Not too bad.My mate's 2007 GSXR750 reads 108 to the GPS's 100.  Probably a good thing!

An 1150RT I used to ride was 10km/h optomistic.The 1200RT I get on occasionally is just as bad, reading 110 at 100.I figure that by riding at the indicated speed I am by necessity saving fuel and avoiding the risks of speeding tickets and crash risk.Can't be bad.

It's not just bikes. My new Hilux shows 110kph and the GPS reads 103kph. Although I have to say it is linear.Makes my complaints about getting a ticket for 113kph seem weak 😳

Ive found all BMW speedo bikes and cars we have owned are within 4kph. Most of the Japanese cars we have had have been minimum 10% slow.

Lucky then, that we didn't go fast then :-D.  My speedo is miles out. I never speed, yet it shows all sorts of weird numbers. Maybe I should get a GPS.I think the GPS error was removed a few years ago. I was told that it used to be a couple of hundred meters out, but now it's pretty much spot on.