Wisconsin Lawnmower Racing Association Racing Classes
GP– Stock motor governed at 3650 RPM, unregulated gearing, single cylinder overhead valve and valve in block L head, with maximum factory rating of 33 cubic inches.
GP (POWDERPUFF)– This girls-only class gets just as fast and are every bit as competitive as the boys! All GP rules apply to this class. 16 years or older to race this class
GPT– Prepared governed V-Twin , governed 3650 RPM engine, 20 hp and under,All GP rules apply to this class.
A/P– 4-stroke engines 10.5 hp and under with a factory maximum stock original displacement of 22 cubic inches must provide spec’s (This includes all engines both Valve-in-Block L Head and Overhead Valve with a maximum displacement of 22ci)
S/P– Valve in block 4-stroke engines over 8.5 HP
C/P– All Single cylinder OHV and twin cylinder valve in block, 4 stroke engines, 20 HP and under
B/P– All OHV V-Twin 4-stroke engines, 20 HP and under
J/P– IMOW Rules- Stock motor governed at 3650 RPM, Single cylinder valve in block or OHV not to exceed 33 cubic inches, with a 8-1 gear ratio (AGE 10-15)
GP/K- GP RULES– Stock motor governed at 3650 RPM, unreguated gearing (AGE 12-15)
GRASSCAR JUST ISN’T ENOUGH SO….WILMRA RACES THESE ADDITIONAL CLASSES, THESE ARE NOT NATIONAL CLASSES BUT A WHOLE LOTTA FUN!!!!
GPT– Twin engines, governed 3650 RPM engine. 16 years and older to race this class. 20 HP and under, ALL GP RULES APPLY TO THIS CLASS.
GRASSHOPPERS– 212cc (6.5 Hp) clone motor, Centrifugal clutch (no disk clutches), 6 inch rims with a 8-1 ratio, Governed 3650 max.RPM Designed this unique class for kids age 8-12.
RULES TO BUILD GRASSHOPPER!!!
These proposed regulations would be specific to this class and are supplemental (as with all rules specific classes) to the general mower requirements of section “VI.” in the USLMRA rulebook.
• This class is for children ages 8-12 years of age. A parent or guardian must be present whenever the child is on the track. The driver must be able to reach and operate all of the tractors controls. All drivers must demonstrate that they can safely drive and control their mower before they will be allowed to race other mowers.
• May use mid engine (AP style) or full size front mount chassis configurations in this class.
• 34” minimum unaltered wheelbase with 40” required width (outside of tire). No offset is allowed.
• 6” maximum rear rim diameter with maximum 13” diameter rear tires (i.e. 13 x 6.50 x 6). 13.25” dia. @ 15 PSI maximum allowed rear tire height.
• Front rim size 4” minimum diameter with 13’ maximum diameter tires.
• Tractor style seat with minimum 4” high side bolster secured. Seat to be mounted at a minimum elevation of 13” (top of rear tire).
• 4” minimum frame height. Nothing to extend below 2” clearance from the ground (i.e. steering, deck halves, running boards).
• Running board must be wide enough to prevent the child’s feet from reaching the ground. Nerf bars in accordance to the general build requirements are recommended but must be designed as to disallow any chance of entanglement.
• Rear bumpers are required. An additional central hoop (maximum 16” wide) may rise to a maximum height of 2” below the top of the seat for additional driver safety. All other Rulebook design requirements apply. No front bumpers are allowed.
• Mowers must have functional axle mounted brakes. Brakes to be actuated with a foot pedal control. No jack shaft mounted brakes will be allowed.
• Drivers must wear all required safety equipment whenever they are on a running mower.
• Mower must have a functional, tethered commercially available kill switch.
• Engines to be 4 cylcle 9 HP or less. Both horizontal ( 320 cc max) and vertical (19 ci max) will be allowed.
Engines must remain stock governed 3650 RPM maximum. All components must be as supplied (including air cleaner) with the exception of the exhaust. Direct replacement air cleaners and spark plugs are acceptable. Refer to general build requirements of the USLMRA rulebook for proper exhaust requirements. Ratio from the engine to the rear wheels will be no less that 8 to 1 in the highest gear. No lockouts are allowed. Mowers must use a go kart drum/shoe style centrifugal clutch. No disc type clutches will be allowed. Steering wheel mounted throttles will be used. When the throttle is released the clutch must fully disengage ( no creep will be allowed). Carburetor must have double return strings attached to the carburetor throttle shaft, attached at 2 different locations.