2012 FIM Technical Rules Motocross

01.26 DEFINITION OF A FRAME OF A SOLO MOTORCYCLE
The structure or structures used to join any steering mechanism at the front of the
machine to the engine/gear box unit and to all components of the rear suspension.
01.27 STARTING DEVICES
For specific details, refer to this article of each discipline (CMS, CTR, CEN, CCP).
01.29 OPEN TRANSMISSION GUARDS
For specific details, refer to this article of each discipline (CMS, CEN, CTR, CCP).
01.31 EXHAUST PIPES
Exhaust pipes and silencers must fulfill all the requirements concerning sound
control (see also Art. 01.79).
31.01
The end of the silencer must be horizontal and parallel (over a minimum distance
of 30 mm) to the central axis of the solo motorcycle (with a tolerance of ± 10°) and
must not exceed the end of the silencer body by more than 5 mm. All sharp edges
must be rounded with a minimum radius of 2 mm (See diagram E).
31.02
Exhaust fumes must be discharged towards the rear but not in a manner as to
raise dust, foul the tyres or brakes, or inconvenience a passenger, if there is one,
or any other riders.
All possible measures must be taken to prevent the possible loss of waste oil so
that it does not inconvenience a following rider.
31.03
The extremity of the exhaust pipes on solo motorcycles must not pass the vertical
tangent of the rear tyre.
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General(e) Section