I think on your model you will have to connect it to your noise filter, god knows were that is but having said that the twin cams have a twin coil pack...so u just cant hook it up to the negative side of the coil. Doing this will give u half of the reading since there is only one spark per crank revolution instead of the 2 that is required for correct oppeation of a 4cyl mode tacho. I think the best solution would be to ring around some auto elec's or send ot back and get a 2cyl tacho which would work just like normal

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ORSMREX