Hitchcocks Forum

Like most others, the speedo of my Sixty5 is wildly inaccurate - I'd say it's a good 30% too fast, which I have learned to live with. But does that mean that the mileometer will also record "fast" to the same extent? (So that, although there might be 9000km on the clock, it might have actually only travelled about 7000km?). Are there any opinions on the accuracy, or otherwise, of the mileometer?

Yes, mileometer will also run fast!

If speedometers are fast, why did I get a speeding ticket on my 2000 Bullet? Supposedly doing 78 in a 70km zone. Confused of Brisbane.

No in fact the odometer is unrelated to the accuracy of the speedo to a large extent at any rate. The miles are measured via a direct worm drive from the speedo cable so assuming the tyres and wheels are the right size and the speedo gearbox is right the odometer should be pretty reliable. The speedo on the other hand is basically just a steel flat bottomed cup a bit like a smaller version of a Kiwi shoe polish tin lid inside of which spins a disk magnet. The needle of the speedo is attached to the tin lid as is a hair spring that returns the tin lid and needle to the stop. As the disk magnet is spun by the cable the tin lid is dragged around. The fast the spin the further the lid is dragged. All this means that there is only really one point at which a magnetic speedo like this is accurate and this is generally set at the most important speed say 50 mph. I recently rebuilt the Veglias on the old Ducati and using a lathe and an accurate tool rpm measured I was able to re calibrate what had been pretty useless gauges. I spun the gauge at what I knew was a rpm that should produce a speed of 100 kmph and then reset the needle a that it was indeed so. They do require cleaning and lubrication after a number of years of neglect.

Simon's right.

Yep, Checked against a GPS unit the mileometer on my '99 Bullet is suprisingly accurate while the speedo was way off. I noted where 30 and 50 were and painted thin lines on the glass so I knew where the two most important speeds were. (I didnt have to worry too much about the 70!).

Thanks all, especially Simon for the very useful info! I have heard of people spraying some WD40 in the bulb aperture of the speedo to improve it, but I would rather live with it's erratic behaviour than risk getting some gunge onto the clock face! Re-assured about the odometer now though!

Why not check it over a known distance?.

WD40 in a speedo, don't do it.

"Are there any opinions on the accuracy, or otherwise, of the mileometer?" Well, I know diddly-squat but I think as a MILOMETER my ODOMETER performs poorly, as it records in KILOMETRES........ "Does it matter?", I hear you ask. Well, yes.... when you're trying to follow a route sheet marked entirely in miles, it's a p.i.t.a.

km is 5/8th of a mile. 160kms near enough 100 miles. You get used to it. I have to convert the other way having a speedo in miles in a metricated country.