RACEPAK Avenger II RPM Input (were to connect???)

I am installing a RACEPAK Avenger II EGT/Temp/RPM gauge on my 05 Summit REV 800 and I am having trouble finding the right wire to tie into to get a tach pulse. All accessory, lighting and instrumentation power is provided by one wire which goes thru the relay and than splits and goes thru 2 fuses. One is for the headlights and the other is for everything else. This line is regulated and does not provide a pulse signal that can be used to trigger the tach.
There is a wire that comes directly off of the Magneto and goes directly to the Speedometer connector but isn't labed as to what is for. I assume this is the trigger for the Tachometer. Does anyone know for sure. If so, is this the correct wire to tap into to get my RPM input for my Avenger II?
I am positive that there are many folks out there that use or have at one point used a RACEPAK gauge and can tell me were to hook this too.
Thanks in advance...

Thanks for the feedback. I had thought about using that for the location to tap into but (circled in RED onthe attached picture) also wanted to nkow if anyone has tried the White/Green wire (highlighted in GREEN) which goes directly to the Speedo/Tach so I think it is the tach signal. It would much easier to tap into it since it is located directly underneath of the instrument console and not down low in front of the motor. Any thoughts???

I actually tried the white/green wire really quick and it it made both displays flash with some number ????? I ended up using one of the 2 yellow wires before the voltage regulator and it works fine. It was just a lot more work than on my Arctic Cat

I have a 3-wire.
RPM Input (yellow) - Hooked to Yellow wire off of coil.
Power Source (red) - Hooked to Red/Yellow wire for acc. jack.
Ground (Black) - Hooked to chassis

It appears to be working fine.....is there a problem with using the yellow wire instead of the green wire???