The MCI Guide to Moped and Motorcycle Exhaust System Markings

This guide is set up to help the police identify illegal exhausts on mopeds and motorcycles in England. It is designed to identify the main problems of exhausts today from noise to custom fitted performance enhancing extras. The report is split into several sections to point out the most common failings on exhausts in order for the police to prosecute persistent offenders.

This report can also help all bikers by showing, what is legal and what is not. By keeping to these set guidelines set by the Department for Transport you can keep you motorcycles/mopeds legal on the road.

Subjective Identification

The noise limits imposed on new motorcycles have been very stringent for many years. Certainly any motorcycle fitted with an efficient original equipment (OE) or replacement exhaust system (RESS) is most unlikely to cause offence or be illegal. This means that if a motorcycle "sounds noisy", its exhaust system is probably illegal and is worth inspecting for the appropriate markings.

Illegal Exhaust Systems


These generally fall into two categories; the poorly maintained, and more commonly, the "race or custom system". The later are in widespread use and are particularly popular among the riders of "race replica" and "custom or "chopper" style machines. Race and illegal custom silencers should bear the marking "not for highway use" or similar wording, however this may have been erased or removed. It is therefore highly probable that the exhaust system of a "noisy bike" will either be unmarked or have "not for highway use" marked on it. Either way these are evidence of an offence.


Markings and their Locations

These are required to be "indelible and clearly legible, even when fitted to the vehicle" (C&U and 92/61 Annex V). A popular practice among illegal RESS manufacturers is either to use chrome foil stickers or to "hide" the markings on the inward face of the silencer or in another inconvenient location.

Table 1: Original Equipment Silencer Marking (mopeds and motor cycles)

This table refers to the exhaust Systems fitted to machines when they were made.




Table 2: Marking requirements for mopeds and motor cycle silencers in-use

This table refers to the markings that should be on any motorcycle, scooter or moped being use on the road except for machines first registered before January 1st 1985



Table 3: Marking requirements for silencers/exhaust systems at Point of Sale

All replacement silencers/exhaust systems offered for sale must be marked:



Table 4: Noise Limits for Motorcycles (for Information only)



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