Moped silencers

[Futurama]

Are mopeds and motorcycles restricted in the amount of noise they can emit? I suspect that they are fitted with silencers but I've heard that sometimes they are removed to improve speed or performance.

[Harley]

All motorcycles of 175 cc and above are limited to a maximum noise output of 80 db (A) with smaller machines with commensurately lower limits. In the UK replacement exhaust systems must be CE or BSI marked to indicate that noise from them is not significantly greater than from original equipment exhaust systems and silencers.Modern motorcycles are complex machines and removing the exhaust could have a negative effect on performance as the gas flow from the engine could be affected. The noisy bikes you hear have "race" silencers fitted that add a small percentage of power, it's more for the "sound" than the performance. The amount of power a superbike puts out is far more than a rider would need for public roads. If the exhaust isn't EEC marked the Police can issue an on the spot fine and a fix notice.At MOT time the owners put the original silencer back on, it takes 2 or 3 minutes!

[Impret-Sir]

As Harley has said, bikes with overly noisy exhausts give the nit-wit riding it the impression of extra speed and power, but in fact usually have the oposite effect.

[PhilBy]

Exhausts can be used as a means of restriction, don't know about the latest models but the older mopeds usually had a washer put in at the manifold end. Most motorcycles are rescricted by having carb tops fitted that prevent the slides from fully lifting.

[Zero00]

Actually these new 'race' pipes do have a purpose they increase speed considerably from a restriced ped, the ones these days (like my suzuki katana) have either a side pipe off the exhaust to stop complete flow of the gases making it restricted or a cone in the pipe restricting the flow again,

hope this helps,

Zero