If the connector that's on the bike now, is compatible with the original tachometer, you can remove the individual pins from the connector, and move them .
I'm assuming the pins are round, remove the connector, and you have a little 'free play' of the wire in the connector, push the wire from the backside of the connector, and then place something like a wire 'butt' splice over the pin and push down, it should compress the small spring tab, that prevents the pin from backing out of the connector, and you should be able to pull the wire and pin out of the connector .
Same thing can be done to the flat pin connectors, only difference, is that there is a small slot in the connector where the pin sits, and need to place a pin or other small tool in the slot, to depress the spring tab .