It needs a complete circuit. The spark induces a voltage in the sensing wire that's wrapped around the ignition wire. In order for the tach to see that voltage, it needs something to compare it to, like the frame ground. If you don't do this, the tach will "float," electrically speaking. This would mean that when the spark occurs and the sensing wire sees, say 10V, the entire tach will raise to 10V so in essence nothing changes that the tach can see.
An analogy to describe it better: You are in a car but can't see out the window. The road is too smooth to feel if you are moving or not. How do you know what is going on? Now we give you a window to see the trees that aren't moving (the frame ground). If the trees are moving by from your perspective, then you are moving.
What a freak of nature! That has something to do with scavenging.
So the transfer port needs to be directly across from the exhaust for that freak of nature piston to scavenge correctly, meaning the intake has to be offset, hence the clocked intake slot in the skirt? Then what about the top ring gap?
Ya lost me
Okay, I cheated and looked up what starboard was again. So I'm guessing either V-Twin or something like RG500. So in that case it is about carb mounting? Not sure if there are any V-Twin 2-strokes...
Seems like they didn't want the intake ports directly on the face of the piston that gets the side load from the ignition stroke. But then again, they put the top ring gap there. Maybe that's just how they felt like mounting the carb?
That hurts! The problem in PA is we do it to ourselves in the winter. City people around here can't drive so the roads get metric tonnes of the stuff. Funny the state says we're hurting the environment with chemicals in water runoff and then they do this. Not to mention the salt is killing my beautiful XJ.