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From: Stalterian(at)aol.com
>So, here are my questions:
>Any ideas about why and how to fix the indifferent tach?
>Does everyone's speedometer register such imprecise speeds?
>Is it impossible to find a reasonable OD tranny (and is it difficult to
>install?)?
The tach is pretty straight foreward to fix with a schematic in hand.
Sometimes the addition of electronic ignition causes the smiths tach
to function intermitantly, this is usually fixed by double winding the
coil + feed around the inductive trigger on the backside of the tach.
see
http://www.corpdemo.com/tiger/techtips/motach.html
The Author,
Mark Olson
1-408-765-4490
Should be able to assist if this can not be straightened out.
The problem with the speedo is usually attibuted to a worn
jewel in the speedo drive coupling. This is a piece of saphire
used as a bearing in the piece that connects to your speedo
cable.
It is normal for these to wear, and a provision was provided
for its adjustment if needed.
The adjustment inside the speedo unit, and tweaks the tension
on a thrust plate, which takes up the slop in that bearing.
I seem to remember that the front plate has to be removed
to gain access to the adjustment screw, so the speedo
will have to be removed and carefully dissassembled.
The adjustment is pretty touchy, and is correct when the slop
has been removed with very little tension on the spindle.
The speedo needle should not stick when the needle is
moved manually to 5mph or so.
Final testing can be performed with a drill motor, and
a square cut bit which will couple the drills rotation to
the speedo.
If it doesnt jump arround, chances are it will work in the car
when you put it all back together.
I have rebuilt 2 speedos with the same symptoms, both
successfully.
Hope this helps,
Jarrid Gross
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