Its a matter of wording, but the two cylinders on a V twin cannot both fire at the same time, because the front cylinder reaches top dead center 90+ something degrees after the rear cylinder (the 650 and 1100 engines spin the opposite direction from the front wheel).
What the mechanic is saying is: the cylinders are suppose to fire on alternate revolutions of the crankshaft. While one piston is on its compression revolution the other is on it exhaust revolution.
If someone accidentally or intentionally changed the position of the front cam shaft (timing) so the rear piston fires, then 90+ degrees forward the front piston fires, then the crank goes around and both exhaust on the same revolution... that is what the mechanic is saying. The two pistons would fire so close together it would sound like they fire at the same time. If you put your hands over the exhaust you should be able to feel it at idle speed.
Im not sure about this, but I think some Harley engines are set up this way, and that is why they vibrate like a paint can shaker.
Its possible a previous owner changed the timing on the bike intentionally to make it run this way. If thats the case you dont have to change it back, unless it bugs the hell out of you to ride it that way.
Its also possible someone changed the timing chain or tensioner, or replaced the starter clutch, and dropped the timing chain, had to align the timing again and got it off 360 degrees on the front cylinder.
Since the 1100 does have a problem with the starter clutch if you rev the engine will you are starting it... I guess both causes are equally possible.
BTW: this does not happen very often - I think this is the FIRST time this has come up with a Vstar bike.
Last edited by KCW; 11-18-2018 at 10:45 AM.