How to install into Rebel 300/500/1100 header pipe:
The $15 Shorty GP baffle/catalyst – The Rebel 300 can use any muffler and still have a catalytic converter. You just add a $15 Shorty GP baffle/catalyst to the header pipe. How to install: it is a very tight fit so use a hammer to flatten it a small amount where the bolt fitting is. Then hammer it lightly into the header pipe. Leave about 5 mm of the baffle protruding so it can be removed later. Put a 25mm long bolt about 40 mm up into the muffler inlet to “catch” the baffle in case it becomes dislodged. My guess is the $15 Shorty GP baffle/catalyst provides maybe 50 to 60% of the catalytic converter function compared to the stock one.
The factory cat weighs approximately 7 ounces (198 grams) – the Shorty catalyst weighs 2 ounces (57 grams). The factory cat fills the exhaust space, where the Shorty catalyst has about a 10% gap if you mount it in the muffler, which you could fix with a sleeve.
The Rebel 300 muffler inlet/front is 1 11/16 inch ID or 43 mm. The Shorty GP baffle/catalyst is 40 mm OD and 40 mm length. The 300 cat is 5.38″ 137 mm) from the end of the muffler, probably to keep heat away from the muffler joint – so if you put it in the muffler, I would mount the Shorty GP catalyst at least 4″ (100 mm) from the end of the muffler. Make sure that you fully tighten the mounting bolt before starting engine (otherwise catalyst could move further into muffler and become stuck.) The Shorty catalyst is 40 mm long, so there is plenty of room to add a second one if you want it to be quieter. You could also mount the shorty in the header pipe, as described above.
Rebel500 