Mechanical speedo misread

Ness · L Plate Warrior Joined: 14 Nov 2015 Karma :

Hi all, new to the forum and could do with a bit of tech help please.

I'm back on a bike after a 7 year hiatus and have bought a dirt cheap 1994 CBR600 F2 streetfighter which is a total rat. It'll do me for a year or so though.

Anyway, being stripped naked, the dash has gone and has been replaced by a small, individual speedo and tacho. The problem is with the speedo. At about 30mph it's reading 80. I've seen a needle bouncing all over the place or not working at all but never anything like this.
It's a mechanical speedo and the cable is clean and spins freely. Obviously too big of a difference to be a mph/kph swap.
I know wheel and tyre size can alter readings but only fractionally otherwise there would be dozens of differently calibrated speedos on the market.

Anyone have any ideas on what's causing this?

Cheers

Copycat73 · World Chat Champion Joined: 11 Jan 2013 Karma :

a jpg. of speedo would be usefull but my best guess is that the fitment is off a trials bike with a 21 inch wheel so the ratio is way off ...
buy another intended for a 17 inch wheel.
____________________
Whatever I post I have no citation and no intention of providing one..
caveat emptor

Ness · L Plate Warrior Joined: 14 Nov 2015 Karma :

Cheers for the reply.
I hadn't even considered your reasoning as the gauge is a bog-standard, unbranded, chrome one usually found on 'fighters and customs. I'd kind of resigned myself to getting a new one but didn't know if anyone had come across this problem before.

It seems a bit stoopid that someone would go to the effort of a conversion and then put a totally unusable speedo on!

Copycat73 · World Chat Champion Joined: 11 Jan 2013 Karma :

Ness · L Plate Warrior Joined: 14 Nov 2015 Karma :

Like I mentioned, it's a rat-bike and I knew it needed work doing when I bought it. The loom is a bit of a bodge too. It works but could do with stripping out and starting again.

To be fair, the engine cover is scuffed which is probably why it was made naked in the first place. Cheaper than buying new fairings Rolling Eyes

As long as it lasts a few months to get me back into the swing of riding again I'll be happy.

Oh, and I know those types of people too. An old boss of mine had an LTD 440 which had tassles hanging from the ends of the bars to match his fringed jacket Laughing