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What would happen if you overspeed a speedo?
Posted: Wed Nov 14, 2018 2:14 pm
by stinkwheel
I've got quite a nice 80mph smiths-style speedo I got on a bitsa bike I bought -it may even be an original one, there was a mix of Indian bullet and Meteor Minor parts on it, the ammeter is definately 60's-.
If I went significantly faster than 80mph (the bike ought to crack 100mph) would it break anything other than the speed limit? I remember my tomos moped used to go right round and back up to 15mph again but it didn't have a pin at zero.
What would happen if you overspeed a speedo?
Posted: Wed Nov 14, 2018 5:21 pm
by Mark M
I think it depends if it is a Chronometric or a magnetic. If a Chronometric you will kill it as it is essentially a clock mechanism and we all know what happens if you over-wind these! A magnetic might survive but I wouldn't risk it. A workmate and I once ran a Transit off the clock on the M1 and it stuck at +15 mph ever after!
REgards, Mark
What would happen if you overspeed a speedo?
Posted: Fri Nov 16, 2018 10:35 am
by John L
stinkwheel - First thing is to determine whether it is an actual Smith's speedo. or merely an Indian-made unit with an imitation "Smith's-style" face.......shouldn't be too difficult. There are plenty of pictures on the internet to help you decide.
Does it have a trip counter ? Is there a white line at 30mph or 40mph ? Can't say what would happen if you overspeed, but if it's an Indian-made head, I imagine it wouldn't last long. Other opinions are available.....
What would happen if you overspeed a speedo?
Posted: Fri Nov 16, 2018 5:18 pm
by John R
I used to have a Citroen 2Cv with a speedo that had a pin at 80 mph. It was pretty speedy as those cars go, and would frequently go up to the pin on a long downhill on the motorway. Never did any harm.
What would happen if you overspeed a speedo?
Posted: Fri Nov 16, 2018 10:35 pm
by Scalyback
If it has a trip meter then it is probably an original Smiths chronometric. Best test? speed the drive or bike up slowly. If it is a chronometric, the needle will jump as it updates every 3/4 of a second. If it increases smoothly, then not a chronometric.
See vid below which shows a chronometric...

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REOC 15084
Tabellarius de verbis. Ostensor gaudium[/center]
What would happen if you overspeed a speedo?
Posted: Sat Nov 17, 2018 12:06 am
by stinkwheel
No trip counter so probably Indian. May be a case of "suck it and see" then, if it's an Indian one, it won't be worth much. If the needle flicks like the video when I try it, I'll take it off again before trying to exceed the speed limit.
What would happen if you overspeed a speedo?
Posted: Sun Nov 18, 2018 10:16 pm
by Adrian
OK, FOR ILLUSTRATION PURPOSES ONLY, there's a genuine chronometric speedo with flanged bezel for a casquette/nacelle headlamp pictured (from the side and underneath as well) on ebay, item 332888950993 .
Meanwhile our hosts stock the Indian replica chronomentic (in a non-chronometric kind of way) 80mph speedo, piccie here:
http://accessories.hitchcocksmotorcycle ... tyle/37813
These also have an odd-shaped body rather than the usual short fat cylinder shape.
A.