Home › Forums › General Discussion › Buy and Sell › DR650. Aftermarket muffler and jets › Reply To: DR650. Aftermarket muffler and jets April 30, 2019 at 10:38 pm #29618 Tyre kickerParticipant Location: Bike: Rank: 50cc Rider Hi oldbeer. Pipe OD at actual end of header is 45 mm. This is the size of the expanded bit that the muffler fits into. That is what you asked for ! …Lance.