2008 PRA Sound Rule

For the 2008 season, all members of the Palmyra Racing Association with riding privilege on club grounds will adhere to the following exhaust equipment guidelines. Failure to comply will result in the termination of the violator’s membership.

4-Stroke Motorcycles
As a general rule, 4-stroke powered off-road motorcycles will employ a properly functioning and well maintained exhaust (muffler) that incorporates a mechanical baffle in the form of an internal turbine or a seven-disc “Supertrapp” style end cap, (where the seventh disc is a solid plate). Exceptions to this rule (subject to change) currently include motorcycles not intended for closed course competition, (XR400, DRZ400, WR450, etc) and 250cc and 150cc motocross models (YZ250F, CRF250, CRF150 KXF250, etc)- these bikes are currently allowed to run unadulterated stock systems
2-Stroke Motorcycles
As a general rule, 2-stroke powered off-road motorcycles will employ a properly functioning and well maintained OEM exhaust (silencer) or an aftermarket unit meeting or exceeding minimum length requirements. OEM and aftermarket units may not be altered from their original design or specifications. The minimum lengths for aftermarket silencer canisters (not including end caps) are: 

· 8” for 80’s

· 9” for 125’s

· 11” for 250’s

Approved Equipment list for 4-Strokes
To our knowledge there are only two turbine baffled exhausts manufactured at this time- the FMF Q Series and the stock KTM EXC and MXC (not SX) model exhausts. Concurrently, the only known “Supertrapp” disc-ed exhaust is the White Bros E-Series. At this time, the only other approved options are an otherwise unchanged OEM unit fitted with a seven-disc baffle (seventh disc to be a solid plate) or one of the approved systems listed below with the quiet insert installed. Disc type end-caps are currently offered by BMP (www.bmp.motox.org) or can be built by mating a disc system (from White Bros, FMF, BMP, etc) to a solid end cap like those available from Pro Moto Billet and Dr D.

The only exhausts currently allowed on 4-stroke motorcycles are:

250 4-strokes	450 4-strokes
Unaltered OEM*	OEM Fitted w/max 6 open discs + solid end
OEM Fitted w/max 6 open discs + solid end	White Bros E Series w/max 6 open discs + solid end
White Bros E Series w/max 6 open discs + solid end	Dr. D spark arrester exhaust system w/insert
White Bros E2 w/spark arrester insert	FMF Q Series
Big Gun w/ vortex quiet insert	DB-Dawg Insert
FMF Q Series	Chris Wahl's “ C dub ” insert
Dr. D spark arrester exhaust system w/insert
*  Unaltered OEM systems are also allowed on woods/off road bikes such as the CRF250X, WR250F, 400EXC, etc

Using any other system not included on this list is a direct violation of the PRA Sound Rule subject to Board review and membership termination.

· Obtaining a Variance
So as not to shut out other potential solutions that may be offered by the exhaust manufacturers or elsewhere, club members will have the opportunity to create an exception or add to the 4-stroke approved equipment list for 2008. It does not matter what the magazines, dealers or manufacturers say – ONLY THE PRA BOARD can authorize/approve additional exhaust systems by unanimous decision of the entire board. To be considered for a variance, an exhaust solution must, per the standard MIC sound measurement process, be at or below the following minimums;

	Half Redline	Half Redline Plus*
250 cc	93.4 dba	95.5 dba
450 cc	92.8 dba	96.5 dba

* Where "Plus" is equal to 1000rpm for 250's and 1500rpm for 450's

It is advised that you consult with the PRA Board prior to purchasing a potential solution as many exhausts were tested in the development of this rule.

Caveat
This rule is subject to change/update at any time. Should we discover new issues along the way, (i.e. a particular model bike identified as a “problem”) tougher, more detailed sanctions may be imposed. Additionally, the PRA Board and the Distant Riders reserve the right to sideline an individual should an issue be suspected/discovered regarding the condition of said individual’s exhaust.