I have been seeing some exhausts the the rear cylinders exhaust pipe exits and goes towards the left side of the bike, others i have seen the rear exhaust exits out and goes towards the right side then goes back under the bike.. Whats the difference in these systems?

 

The true duals I just bought both go out on the same side as stock. I have seen the type with the U bend in the rear pipe and the exhaust going out on both sides of the motor. When I got mine they told me that they both work and flow the same, it is just what look you like.

 

rear cylinder header pipes are often "pretzeled" one way or another; a.) Harley's work best with a specified diameter and length, so design wants to get close to that length.
b.) the 2 pipes want to be equal length, so the rear has to add bends to make up the length.

* some POOR designs have the pipes keep the rider from checking the oil or tranny fluids...

link to exhaust notes:
http://www.nightrider.com/biketech/c...austlength.htm

mike

 

So basically they are the same then? It seems like when the pipe breaks off going left it fills the empty void behind the motor a little better...

 

If you are talking all OEM systems, then Model year is the difference, 09 started the cross under system that replaced the rear "Y" pipe design. Otherwise you may be seeing aftermarket true duals, many manufacturuers, all a little different but basically the same, with the rear pipe exiting the left side.