T H E  O L D  G R E E N  B E E M E R RIDING A 1974 BMW R90/6 FLAT TWIN

OPENING UP THE EXHAUST MUFFLERS If you are looking for a way to let your R/? bike produce a bit more punch from the pipes then there is no need to shop for new mufflers. Make or get yourself a drill bit extensioner and do the following. First drill a small pilot hole in the plate at the end of the conical ( megaphone ) section of the muffler. Enlarge the hole up to the point you are satisfied with the sound, I went as far as 16mm and additionally drilled an extra 8mm hole at the end of the reversed cone at the end of the muffler, opposite the condensation vent hole. This gave me the punch I was looking for, strong not loud, acceptable by other roadusers and the neighbours in my street but a lot more powerful. Drill the separation plate at the end of the megaphone ( 16 mm ? ) and / or drill an extra hole opposite the condensation ventilation hole. I drilled the separa tion plate with the mufflers still mounted on the bike with the help of a drill extension tool. This way I was able to take the bike to the road in between drill sessions to see / hear what would happen next. A bit more punch from the pipes but still decent enough. Carburettor jetting was left as it was. Opened up the idle screw settings slightly ( richer ). Drove many years since, spark plugs look perfect ( coffee ). To keep these silencers alive for a loooooong time, remove 'm from the bike fill the inside with boiled linseed oil, shake, roll, make sure the stuff goes everywhere and drain the excess back out. Leave 'm standing upright for a few weeks, the longer te better, to dry on the inside. Don't forget to clean the outside as backed in linseed oil is hard to remove. Repeated every few years these pipes will serve you forever. Continue to Points Ignition Back to BMW R 90/6 maintenance index / Home EM rev 2021 A A R D  V A N  H O L L A N D . C O M