does anyone know how i can use a mechanical motorbike speedo on my car? with a bike engine!

Simple answer is bloody difficult to do as a bike withe cable/mechanical speedo takes its drive from a speedo drive gear that fits onto the front hub/spindle of a bike. I really can't think how you would be able to incorporate this setup onto a locost type car. Unless you could mount the bike speedo drive onto the front hub of the car. What engine/speedo are you using? You will need to find the speedo drive gear for the speedo from the same bike. You will then have the problem of the wheel size difference from car to bike giving you the wrong reading. It really would be alot more simple to use an electronic speedo.
Bloody hell that took some thinking about after 5 tins of Stella!

I don't think it maters too mcu that the speedo is driven ffrom the front wheel hub since you cna get a speedo cable made up to connect to your gearbox.

The problem is about gearing - again there are companies that can fit different gears into the speedo for the odometer - assuming it has smae constriuction as a car on (never peeked inside a bike speedo) plus magnetise the disc so the needle shows correct speed. The latter would be easier to do since the companies that do this may not have the gears, unless they make them themselves.

I am pretty sure I have seen mechanical gearboxes that can change the gearing and there is the third option of an electric motor adapter which takes pluses from a sender to then spin the cable at the correct speed - not cheap though.

In conclusion, it can be done but how much are you willing to spend is what you shouldd be aksing yourself.

phew, so many owrds, so little time .....

I think if you get this working then you will be the only one that I am aware of. The general view is that its not worth the effort even though it would be possible.

old thread

I ended up with a bicycle speedo, which is a bit crap (and not IVA able now).

The sv650 clocks are cheap (£30) and include electronic speedo, rev counter, and warning lights (no handbrake of course). I think that they look good.

You will still have to get the signals into the speedo at the right rate (either by being lucky with diff ratio, wheel size, or by sorting out an electronic frequency multiplier which you could make or buy).

Matt