we have a 2-stroke lawn mower, it's much better for thick grass than our neighbours 4 stroke but it is also a fair bit louder. Is that because it's a 2 stroke, or would I be able to connect a bigger muffler and make it quieter?

 

its just because its a 2 stroke. a different muffler will screw with the power output on it, so just leave it alone. less or more backpressure in the exhaust will alter the fuel/air mixture, which is quite risky on 2 strokers, unless you enjoy tearing it down every weekend to put in new pistons.