3.5 diameter x 3.14 = 10.99 inches
10.99 inches is 360 degrees, 1 degree is .030 on the circumfrence of the flywheel
The ideal 28 degrees is .030 x 28, .854 total movement from idle to WOT..
The formula works out to .244 times any diameter...244 x 3.5 = .854
If the movement is .250 you're getting a little over 7 degrees retard for starting..
With this information you can put the flywheel on the crank so the timing is 28 degrees, if it is not already there [8D]
The key is not necessary, it's just there for engine assembly..The fit on the taper keeps it from moving..Just put the hub on TIGHT..A few drops of Loctite on the shaft will ensure that it won't move.....