Honda H100A Speedometer over reading by 4 - 5mph

[caprilaser198...]

Hi All,
I was just wondering if anyone could shed light on this issue.

When riding my 1981 Honda H100A, if the speedometer reads 30mph, when I ride through one of those "smiley face" signs it says I'm doing 25 - 26.

Is it common for a speedometer to over-read by 4 - 5mph?

Any advice would be greatly appreciated.

[Itchy]

IIRC the important part of the law is that speedos are never supposed to under report your speed.

So manufacturers set them slightly high.

When people use GPS the speed often varies from what is displayed on the speedo by a few mph.

It shows 31mph on my car speedo but the GPS says 28mph.

It's not that much to worry about.
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[jaffa90]

I find that they all read / display at least 2 mph slower,
also has the bike got the standard front wheel and tyre?

[natefz6]

Tyre/wheel size can make a difference too. At 15% difference that does seem a bit high at those speeds.

As Itchy says speedos tend to always over read a bit but 15% seems wrong.

Is the bike running stock wheels? Could be the happy face is wrong too.
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"no I didn't steal it that's just the way I ride"

[G]

Not uncommon at all.

[stinkwheel]

You're lucky the needle is staying steady enough to get such an accurate reading at all. Most H100 speedos I've seen constantly wobble through an arc which gets faster and wider as speed increases. So flat out, mine does somewhere between 40 and 80mph.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[mudcow007]

[Rogerborg]

Yup, speedometers can never under-read. Bike speedos are allowed to over-read by 10% + 8kph (about 5mph). So at a real 50mph, they can show 60mph.

In practice, all of mine have been well over except for the Lifan LF250B which was absolutely bang on. My Enfield speedo gives a fairly reliable indication of whether you are stopped or moving.
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[Evil Hans]

[tom_e]

My speedo is exactly 10% over at all times according to the GPS on my TomTom.

[kev2b4]

comparing speedo with GPS/fixed camera thingy I have found over the years:-
Vauxhall Astravan speedo reads ~6% high
VW Caddy reads ~ 7% high
Vauxhall Omega auto 5% high
Vauxhall Omega manual ~spot on
Ford Transit connect ~ 7% high
Suzy Hayabusa ~7% high @ up to 70 mph
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[Cosmik de Bris]

I haven't checked mine but in the manual it says the speedo is set to read 5% high.

[Rogerborg]