02.14.2012 - WKA Board of Trustees approves 4-cycle rules changes

02.14.2012 – The WKA Board of Trustees has just approved several clarifications and changes to 4-cycle engine specifications.


Briggs & Stratton LO206

The RLV Model 5507 header can now be used in the LO206 classes. This header is identical in performance to the current RLV Model 5506, but it relocates the pipe to clear the rear bumper in some kart chassis. Both headers are now legal.


The Briggs & Stratton Green Air Filter #555729 is now the only approved air filter for the LO206 engine family. This change will eliminate one more variable in the engine specifications and help control costs in the LO206 classes.


Beginning with the 2013 WKA Competition Year (December 20, 2012), the only approved cylinder head for the LO206 engine will be the RT-1. This change will further ensure consistency in the LO206 product as there is a single mold for this head, and this head is used for all Animal and LO206 engines. This change should not present a burden to the current LO206 customers as only the very early engines were supplied with other model heads, and these old heads should have cycled out of the system by now.


Briggs Animal

Recently WKA announced that the Burris aftermarket piston was approved as a replacement part for the Animal engine. However, the piston pin supplied with this piston is not approved. It was found to be 4 grams lighter than the stock Animal pin.


Also, WKA is clarifying the method for measuring the inside diameter of all Briggs piston pins. The pins are to be measured at the outside end of the pin hole. The I.D. should not be measured further inside the pin.


Finally, aftermarket cam gears are now allowed in the Animal Modified engines that run in the Gold Cup and National Road Racing Series. Stock Briggs & Stratton cam gears continue to be required in all other Animal engines.



Several changes have been made to the Clone engine specifications and inspection procedures. The new Clone flywheel part number BSFW-1 is now approved but not required in the Box Stock and Pure Stock classes. Aftermarket billet flywheels continue to be required in the Builder Prepared classes.


A new specification has been added to the Clone valve train. The installed height of the valve is a minimum of 0.815”. Valve spring shims are now allowed.


The 0.019” specification for the low speed jet has been eliminated. However, the jet may not be drilled through to the outside of the carburetor. This will be a post-race tech inspection item.


Finally, the stock Clone rod may now be honed.


Briggs & Stratton Raptor

The stock Briggs & Stratton Upper Retainer part number 23184 is in short supply. As a result, any upper retainer up to a maximum thickness of 0.058” is approved.