I think you can live without a tach, but I think you should figure out your oil pressure and temp gauges as soon as you can! They're pretty important! Let us know how it goes!
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The temp is because the transmitter doesn't work, but the oil pressure, still do not know, any suggestion what should I check?
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On the twin cam, oil pressure indication is mechanical. I would disconnect the oil pressure line and fitting at both ends and make sure nothing is plugged it up. Have the oil pressure gauge checked out to make sure it is working or install a known working gauge to make sure you have oil pressure.
The oil pressure port is located on the right side near the front below the distributor, see picture.