I found a super article on Speedometer repair and calibration at
http://ourworld.compuserve.com/homepages/arhodes/Speedo.html - using
this I have just recalibrated my speedo. It is now reading the correct
54 mph at 3000 rpm. At lower engine speeds it is reading anything up
to 9 mph high (at zero rpm), and at higher engine speeds it is reading a
little low. This, according to the article cited, is apparently a
symptom of the bar magnet losing its magnetism. I can't be bothered to
replace my speedo with a good one, since that would mean hours spent
winding the odometer forward, but at least I now know more-or-less what
speed I am doing on country roads and motorways...
Thanks to everyone who provided help and advice.
Michael Hargreave Mawson, author of "Eyewitness in the Crimea"
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