What could be causing the following. Tach is fluxuating while running wide open. Also, just noticed that as I am turning the key to start the tach rises while cranking.

There is more information needed, but you first need to understand how a tach. works.

It is not a perfect science. The tachometer needle is simply being moved by electrical pulses from the negative side if the ignition coil.

What you are likely seeing as far as the fluctuation is either a loose connection, unstable ignition system, low quality tachometer or incompatible tach./ignition system.

Fill us in on what you are running and we may be able to answer more accurately.

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