Speedo out

[keithbuckby]

I checked my speedo against my GPS the other day, 10KPH out!! I knew it was out a bit, when I followed other cars it was reading 60-70. what would cause this? could the speedo be that faulty, mind you it is an old bike?

[vifferman]

Almost ALL speedos are optimistic, varying anywhere from 2% (my wife's car) to (in your case) 10%. The usual is about 5-8%.
Your bike may have non-standard gearing or tyre sizes, which will mean it's more than this.
Is it a cable drive, or electronic> If it's cable, then the speedo works by a flywheel and spring arrangement. Given that it's now 27 years old, the spring is probably tired and/or corroded, so it is likely to be less springy, so will make the speedo read higher. An instrument repair/calibration place could fix it, but I doubt whether it would be worth doing.
If it's electronic, and the inaccuracy bothers you, you can buy an inexpensive speedo corrector kit from Jaycar Electronics and fix the speedo (but the odometer will underread).

[keithbuckby]

yeah its a cable one, I might try giving it all a decent clean, or just ride accordingly (sp?)

[paturoa]

SV reading 120 is exactly 110 true speed.

[NighthawkNZ:Me]

As vifferman said most speedos are out... and technically if you have a GPS for speed you can use that to pass a warrent if you disconnect your speedo.

Mine is about 7-8kph out at 100kph, its a little more accurate at 50kph
The better halfs bike is about 3kph out at 100kph and the car is about 5

most wll read slower than what the actual speed is. its very rear to get on that is spot on.

[sinfull]

Now thats where the carterton sprints come in handy ! The 955 was reading 241 km when in actual fact i was only doing 226 through the trap !
Shame i didn't have the 1050 speedo on for this last weekend doh !!! But hey it does do 246 km and thats with stock cans and most likely wrong tune !

[Mooch]

With my bike it slightly under-reads eg 245 kmh was timed at 253 kmh

[Pumba]

Shame i didn't have the 1050 speedo on for this last weekend doh !!! But hey it does do 246 km and thats with stock cans and most likely wrong tune !

Man I must be a fat fuck, best I have ever seen on the speedo was 226kph

[sinfull]

With my bike it slightly under-reads eg 245 kmh was timed at 253 kmh

Man I must be a fat fuck, best I have ever seen on the speedo was 226kph

More than likely same senario as Mooch cause im a fat fuck ! I just wish there was another before september so i can try it with the 3into1 on (and a dyno)

[Pwalo]

Another thing to check is that your bike is running standard size and profile tyres.

This can make a bit of a difference on the old cable driven speedos.