I've been fiddling with speedometers for several years with varying degrees of
success and frustration. While the
return spring--which looks like something that came out of a large watch--is a
possible culprit there is often no
obvious cause for a problem. The document by Anthony Rhodes is about the only
reference available, but it doesn't cover
all the possible failure scenarios.
Depending on how much you want to learn about this device and your confidence
with things both mechanical and mystical,
you can either send it out for repair or take a stab at it. I would at least
open up the speedo and have a look, being
very careful to not lose any of the fiddly bits (pretend you're doing brain
surgery). Sometimes the cause is obvious--I
had a cracked odometer gear once which caused the needle to jump at a regular
interval--and sometimes (usually) it's not.
If nothing's obviously broken you can clean the insides with 'electrical
circuit cleaner'--DO NOT use 'electrical parts
cleaner', it will remove paint--and lightly lubricate the moving parts. I
prefer light silicone oil for both the guts
of the speedo and the cable (I've tried everything from white grease to
graphite to nothing for the cable).
Have a look at the cable while you're at it. The adapter, cable, sheath and
speedometer comprise a true system, and all
have to cooperate in harmony in order to get a decent approximation of your
actual velocity.
bs
On 12/18/2010 10:13 PM, Peter & Veronica wrote:
> Gbday list
>
> Yesterday we had our Queensland club Christmas lunch. We drove the BN1 based
> Ward Special about 100km (60 miles) each way. A few miles from the venue, I
> noticed the speedo was reading 120 miles an hour (itbs a 140 mph speedo) We
> were in fact doing about 40. On the way back, eventually the needle went off
> the scale and ended up against the back side of the stop. Currently itbs
> indicating a tad over 140mph, with the car sitting in the garage! I had the
> speedo recalibrated when I got the car about 7 years ago, as it hadnbt been
> changed to account for the carbs 3.54 diff. Since then itbs been pretty
> accurate and the needle quite steady. Any ideas as to whatbs happened?
>
> Cheers
>
> Peter Linn
> Brisbane Oz
> _______________________________________________
>
>
--
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Bob Spidell San Jose, CA bspidell@comcast.net
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