Seepdometer Way Out

[Adam.I]

I have been meaning to post this for a while. My speedometer is wrong. When going at an indicated 22 MPH, I am actually travelling 30 MPH. I have tested this using them roadside signs informing the rider/driver of their speed as approached. Every bike and car I have owned has indicated a speed above the actual speed e.g. my GSX-R indicated 32 MPH at 30. Riding when it indicates below is a bit of a problem. Any ideas what is wrong?
____________________
Veni Vidi Vici

[iooi]

Where is the speedo driven from ?

front wheel or gearbox.
____________________
Just because my bike was A DIVVY, does not mean i am......

[Noxious89123]

If it's from the gearbox, then it's probably worth checking that your running the stock sprocket sizes. Anything else will put your speedo out.

This doesn't apply to a front wheel driven speedo.
____________________
'06 Honda CBR125RW-6 ~ '00 Honda CBR600F-Y ~ '07 Honda CBR600RR-7 ~ Bikeless
'53 Ford Ka 1.3 ~ '03 Vauxhall Astra SRi 1.8 ~ '52 Vauxhall Astra SRi 2.2 ~ '53 Vauxhall Astra GSi

[G]

My RS250 was like that.
As above, if it's driven from the sprockets and you've upgeared, that'll do it.
If it's electronic, you can get a speedo healer device that will sort it.

[iooi]

[Noxious89123]

[G]

Not TOO far off the difference between a supermoto and dirt front wheel. We need to know what bike it is to get a better idea .

[Adam.I]

Forgot to mention, it is a Suzuki Bandit 600 K2. It has got standard size tyres and I haven't changed the front sprocket. Previous owner may have so I will check that this weekend. If that fails, any other suggestions?
____________________
Veni Vidi Vici

[hmmmnz]

some one has changed the sprockets, its 73% out so probably closer to 70% of the original sizes
original sizes are 15 and 47
if they had gone 2 down on the front and 2 or 3 up on the rear, that would just about be right for what you are getting on the speedo
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[G]

But shouldn't down gearing make the speedo overread?
And it's reasonably less likely they would have up-geared that much, I'd have thought.

[Adam.I]

That's what I thought, gearing down will cause the speedometer to over read. This is under reading, and by a massive amount, around 30-40%.
____________________
Veni Vidi Vici

[Kickstart]

Hi

That is a long way for the speedo to be out. Especially as I would expect it to read something close to 33 at a true 30.

Given how much it is out I would suspect that someone has made a mess of an mph / kmh conversion. Maybe an import with kmh clocks which someone has fitted a speedo healer to, and then swapped or modified the actual clocks.

Running ~50% higher gearing would give about that speedo difference, but that would be a massive change to gearing.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Adam.I]

I'm fairly sure it is a UK model, will confirmation of this be On the V5?
____________________
Veni Vidi Vici

[Kickstart]