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MG MGB Technical - Tach needle bounce above 3500RPM

The tach needle is steady as a rock below 3500RPM but bounces +/- 500RPM or more above this. My first though is the that I need a better ground, but....I've also recently replaced the points with a pertronix electronic unit. I don't know if the needle bounce was there before the Pertronix unit was added or not (old age). Thoughts????

Thanks,
Jim
Kalamazoo
James Budrow

This happened to me. The problem was the tach itself.
I think a bearing inside went bad, and slight fluctuations
in RPM would cause the needle to hesistate/bounce.

Fixed with a $25 used tach from e-bay. Another option is to
send it to Nisonger.

If you have the older current driven tach (Says RVI on the
tach face I believe) then certain kinds
of elect. ignition will cause bouncing, maybe check the
archives on this.
Ronald

I've Pertronix on my V8 and the needle swings wildly at 4200 rpm. I have been wondering if it is the Pertronix or the rev counter. The tach is accurate but 250 rpm low.
Any clues??
Ian G Buckley

If I get some time I will email the local Pertronix distributor and see what he says. Also if I get some time next weekend I'll build up an old distributor with a set of points and see if I still have the problem. I'll let you know!

Jim
James Budrow

This thread was discussed between 06/08/2002 and 07/08/2002

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