Howdy Hasso, Triumph mad a few different versions of "their "off rod pipes"
Here is an east fix. Pull one exhaust pipe off. Real simple
loosen the clamp on the pipe at the foot peg area. Now remove the rear passenger peg mount, two bolts. Wiggle the pipe and slide it off. Look in the header side of the pipe you took off. If you see a reducer cone with three tack welds and about a 3/4-1 inch opening you need to remove it.
This will allow the engine to breath better and give you some real Triumph "noise"
If there is not a cone there the pipes are as loud as they can get without completely gutting them.
Best way to remove the cone is drill three or four holes around the tack welds. Run a 1" piece of galvanized pipe through from the other end and punch it out.It's real easy.
Now add some sealant(I prefer Red RTV) to the inside edge of the pipe. Reassemble, let set overnight. Ride and enjoy.
