277 INFO NEEDED

We have no 277 manuals at present. ( I believe the 277 was actually a snowmobile engine - see https://www.rotax.com/en/100-years/historical-vehicles-engines/detail/type-277.html )
Maybe you can check our existing "275" manuals and see if they are similar enough?

see  https://www.rotax-owner.com/en/support-topmenu/engine-manuals#2-stroke-historical-documents

I found a 277 manual on the web at Manualslib.com free to download. The 3rd edition, 1988 manual tells what RPMs and times to run your initial one hour, but not how to wire a tach in. The manual gives details for using it to fly, not run on a snowmobile, but this is the third edition. My system has no battery and no rectifier/ regulator. I used the manual's schematic to see how my engine might vary from the schematic and determine actual wire colors. I am attaching it with my notes to see if anyone knows how my tach gets wired in. 

The most common place to attach a generic tach is to the wire from the Points to the ignition coil.
This will have One 12 volt pulse per spark.
This will give two pulses per rev and the Tach will need to be configured for this.

If you had a generator...
The other method is to connect to the generator wires BEFORE the rectifer.
This will produce a variable voltage AC signal equal to the number of poles in the generator winding.
This could be 12 or 20 poles or something else and your Tach will need to be configured accordingly.
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Your attachments look like what is in the 377-477-503 manuals available in the Historical Documents Section.