Ian,
All the 2-3/4hp instruction I have seen have the same non-engineering method of setting the ignition timing. For those not familiar I paraphrase it here:
When the exhaust valve is just closing, the opposite cylinder is at its firing point. Set the advance/retard control lever midway between full retard and full advance. Turn the magneto so that the points are about to separate (the fiber shoe is just touching the cam.) The magneto can then be installed, the gears meshed, and then secured.
Obviously the ignition timing is not very critical! Make sure if you are timing the front cylinder, you are not firing the rear plug. Else you will find the engine will be very, very cold!
The previous depends on the exhaust timing being correct. The exhaust should close 10º after top dead center, or less precisely, when the piston has descended 1/16”.
If you do not like that method, you could probably use the ignition timing for the 350cc EW model introduced in 1925, which was just an up rated 2-3/4hp. The service book for the 350cc EW says to set full advance for 50º before top dead center.
-Doug
