after market tachometer to coil question

[markm]

Looking for info on tachometer hooking up.
Im helping someone with there bike.
All original wiring is gone and a basic wiring harness has been made.
We have a after market tachometer and wondering which of the tach wires to hook the tach sensor wire to. Maybe someone has wired up a after-market tachometer and can let me know which wires of the coil they used. Thanks in advance

 

[amc49]

May be harder than you think as there are two ignition systems basically, to read the two sides together at two impulses each engine revolution you have to tie the two coils together to read both sides, the problem being, that is a direct short. You have a waste spark ignition there instead of a distributor type. Many aftermarket tachs will not work with that unless made specifically for that type system.

Tach sensor is often the minus side of coil but some few use the plus.

 

[markm]

I cant seem to find a wire to the tachometer only to the tachometer lights. I realize that the tach may read only half or may read twice as much as it should but it will be something to go by. Besides the after market gauge I have put on this bike has both volt and tachometer in it. thanks for your thoughts.

 

[amc49]

Now you begin to see what I'm talking about............................there is NO wire for the tach as the bikes all used mechanical drive tachs that use a cable like the speedo.

I'm wondering why you would be even looking for a wire on a basic harness................................that somebody made. Seems somewhat counterintuitive.

 

[markm]

Ya your right. My xs650 has mechanical tach also but I hooked a electronic on to it. I looked and looked for the tachs feed wire. jeeeze I sure am dumb sometimes.

 

[amc49]

https://www.autosportlabs.com/product/tach-adapter/

That would do it but you gotta solder wires and make up weather proofing. Cheap too. It joins both coil outputs without shorting them out by diodes blocking the shorts.

 

[markm]

that is cool.

 

[amc49]

I've used it on my Ford Focus zetec cars before to get a common electric tach to work, they use an exact copy of the waste spark system these bikes use.

What's so silly is you can pay up to a $100 bill to get the same board, only weather-proofed and from a name brand like Autometer or MSD, that's just crazy. I prefer not to get bilked like that.