first check the engine oil level is correct, as the gearbox could be running in the same oil, then ride the bike a short distance using all the gears, its harder trying the gear lever by hand as it's meant to be foot operated. Buy some exhaust repair paste from a motor factors anywhere, remove muffler, add paste, refit muffler, clamp tight, warm up exhaust gently to set the paste hard.
Pitkin, January 2012