Without a 650 to look at I can't actually look at the marks. But on my 250 there are two timing marks close together and another set elsewhere. The two close-together marks are probably the TDC mark and the ignition timing mark, which will usually be separated by the amount of ignition advance at idle speed.
Most of the old British vertical twins (Triumph, BSA) used a crank with two crank pins positioned so the pistons moved exactly together, almost like a "split single." The valves were so timed that the cylinders fired alternately, or at 360 degree intervals. That gives even power strokes, one per engine revolution, but also gives vibration problems with both primary and secondary imbalances. That is likely where the term "360 crank" came from. The other common crank was a "180 crank" with crank pins 180 degrees apart resulting in one piston up and the other down. That was the configuration used in two-cylinder John Deere tractors for many years. It gives perfect primary balance, but an uneven firing order with firing intervals at 180 and then 540 degrees. It also considerably reduces crankcase pressure pulses and helps reduce oil leaking.
On a V-twin with a single crankpin and a 70 degree bank angle, the front piston will "lag" the rear piston by 70 degrees, or "lead" it by (360 - 70) or 290 degrees. That is the mechanical configuration. If the front piston is at TDC and the cylinder has just fired, beginning its power stroke, the rear piston will be about a third of the way down on its intake stroke.
You are correct that the narrower the V angle the closer the pistons are to moving together. Harley uses a 45 degree V, about the closest of any maker. Ducati and Moto Guzzi use 90 degree V angles. 90 degree V angles give some advantages in balance, but become harder to package in motorcycles. Harley's 45 degree V let them use a single carburetor and a "Y" manifold. Wider V angles make it easier to put two carburetors between the cylinders. The compromises never end. Cruisers also have the really serious constraint of style. It it ain't pretty, it won't sell.
Last edited by Charon; 07-05-2016 at 03:33 PM.