Join Date: Sep 2016
Location: Northern Virginia
1) It is possible if you left something behind in the pipe that isn't supposed to be there and it can't blow exhaust fully, like the core you were drilling out?
2) Doublecheck your enricher, the handlebar change might have torqued/kinked/misaligned the cable or the lever or such and it is not fully shutting off.
3) the exhaust system is designed and tuned like a church organ pipe, for the low end pulsed exhaust, to actually evacuate the piston's exhaust most efficiently, thus a slight loss of lower end torque is the expected result of mucking with the pipes, not severe choking at high rpm. At high RPM the exhaust stream acts as a continuous fluid flow and the pipe "tuning" is less important.
2009 Honda Rebel 250; 2009 Honda Shadow 750 Spirit
"The bravest thing for me to do is admit when I am wrong" - unknown
HRF Answer #1 You should take the MSF Rider Course
HRF Answer #2 You need to clean your carburetor
HRF Answer #3 Sorry we assumed if you didn't say otherwise