2 strokes have twice as many explosions than 4 strokes for the same rpm,so the exhaust note is more high pitched that's why they sound "louder",more "piercing" is prob. the right way to describe it.They are also sensitive to the exhaust system,esp. when high-end performence is concerned.With
proper intake &exhaust tuning they are capable of astonishly high performance.All records in motorcycle racing were held by 2 strokes.Ignition is also critical, the plug fires at twice the rate.It's like comparing a finely tuned but temperamental race horse to a more reliable but plodding Clydesdale.I have allways ridden 2 stroke cycles, ( DKW,Suzuki Yamaha Kawasaki)because of that nice combination of low weight&high power,only the Kawsaki Ninjas are in that class.
A 4 stroke engine is not hurt by the exhaust system but a clogged one (unlikely) can cause overheating which can burn your exhaust valve.But if you have none at all you may warp the E valve upon shutdown due to rapid cooling.Low quality 2 strokes like the HT engines are not worth messing with in my opinion,unless you are a glutton for punishment but the Japanese ones Tanaka,Mitsu. are nice light simple and reliable engines.The Mitsubishi TLE 43 engine has a clever scavenging system that reduces emissions significantly while improving gas consumption