How to clean a yamaha 5 speed catalic converter silencer?

i have a yamaha RXG . i had fitted the catlic converter silencer 5 years before .. recently i have done the entire engine work becuaise the bike used to not have pickup and speed ,. i have bored the block and am using the 2nd oversize piston .Yes my bike duz not have any pickup . the mechanic says the filencer is blocked ....( 5 speed catalic converter silencer ) i dont know how to clean the silencer . con someone help me out .