You can pull a little more rpm out of a stock piped Kawi 650 by removing the headpipe. There is a small hole that injects water about 1 1/2 inches up inside the headpipe. This hole needs to be filled with JB Weld and once dry, a 1/8" hole needs to be drilled into the JB Welded hole. This will dry out the stock exhaust and yield more rpm. Cheap performance.