Racing Your Kart

• Formula Junior C
  
  1. All competitors are between 5 - 8 years old.
  2. Kid Kart with 50cc Comer engine only.
  3. This is a Program Class and will be run on a different course than the cars until the competitor has shown the experience to move to the car course.
• Formula Junior B
  
  1. All competitors are between 8 - 11 years old.
  2. Engines
     
     1. Briggs & Stratton Raptor
        
        1. Fuel: Gas or Methanol
        2. Weight: 245 pounds for gas-fueled karts and 250 pounds for methanol-fueled karts.
        3. Other: Balanced and blueprinted engines are allowed, but no controlled Stock, Modified, Limited Modified, or Open motors.
     2. Yamaha KT-100, only heads with OEM casting "Yamaha" and cylinders with Y3 or Y4 and 787 are legal.
        
        1. Fuel: Gas and Oil
        2. Carburetor and Exhaust
           
           1. Walbro WA55B or HPV1 with WA55B manifold with RLV SSX-V (4-hole)
           2. Walbro WB3A carburetor and 0.600 restrictor plate with YBX exhaust. (3-hole)
           3. If hole exists in pipe for EGT sensor, EGT sensor probe must be in place.
        3. Weight: 250 pounds
     3. Comer K-80
        
        1. Fuel: Gas and Oil
        2. Carburetor, exhaust, and clutch as supplied with engine from manufacturer.
        3. Weight: 250 pounds
     4. Briggs & Stratton World Formula: as homologated except it is permissible to to use an alternate chain/Spricket/gear (type 35)
        
        1. Fuel: Gas
        2. Restrictor: An internal carburetor throttle stop and/or intake restrictor must be used.
        3. Weight: 275 pounds
        4. Battery may be removed.
• Formula Junior A
  
  1. All competitors are between 12 - 18 years old.
  2. Engines
     
     1. Briggs & Stratton Raptor
        
        1. Fuel: Gas or Methanol
        2. Weight: 280 pounds for gas-fueled karts and 285 pounds for methanol-fueled karts.
        3. Other: Balanced and blueprinted engines are allowed, but no controlled Stock, Modified, Limited Modified, or Open motors.
     2. Yamaha KT-100, only heads with OEM casting "Yamaha" and cylinders with Y3 or Y4 and 787 are legal.
        
        1. Fuel: Gas and Oil
        2. Carburetor: Walbro WB3A
        3. Exhaust: RLV SSX-V (4-hole)
        4. Weight: 295 pounds
     3. Briggs & Stratton World Formula: as homologated except it is permissible to to use an alternate chain/Spricket/gear (type 35)
        
        1. Fuel: Gas
        2. Weight: 275 pounds
        3. Battery may be removed.
• K Class (Adult Kart)
  
  1. All competitors are 18 years old and up.
  2. Engines
     
     1. All 100cc kart motors with engine clutch only. Wet or dry clutch. No axle clutches.
     2. Exhaust: Any approved pipe, no adjustable pipes.
     3. Fuel: Gas and oil
     4. Weight: 360 pounds
• F125 (125cc motors and shifter karts)
  
  1. All competitors are 18 years old and up.
  2. Engines
     
     1. All 125cc motors: See SCCA Rules 19.1 for specifications.
     2. Fuel: Gas and oil only
     3. Weight: 385 pounds

• Kill switches are strongly recommended for all 2 and 4 cycle classes.
• All Briggs 4 cycle motors must run an RLV-B91 WKA approved silencer in an unaltered state.
• Exhaust headers including silencer must extend beyond the gas tank but cannot protrude beyond the rear bumper.
• Minimum kart dry weight with no driver or fuel, with engine, is 85 pounds.
• Minimum kart weight with driver can be adjusted on a per event basis depending on weight of competitors at the event. It will be adjusted in the spirit of fair competition and convenience for all competitors. Competitor agreement is required before changes can be made.
• Weights added to the kart for minimum weight requirements must be retained using minimum 5/16" diameter bolts with "nylock" nuts or nuts secured with safety wire or cotter pin. Weights may not be added to Nerf bars.
• Approved fuels for 4 cycle motors are gasoline and methanol, 2 cycle motors can run gas/oil mix only. Fuels may checked for illegal additives at the discretion of the regional Karting chief or tech inspector. Klotz Uplon or Red Line Alcohol Supplement upper cylinder lubrication may be used with methanol to prolong motor life. No other additives are approved.
• Oil samples may be taken from the catch tank or crankcase to be tested for illegal combustion enhancing additives.

• Helmet must be full faced. Shield must be attached to helmet or goggles designed for motorsports must be worn. The helmet must meet Snell M2000/SA2000 or newer.
• An abrasion resistant suit specifically designed for Karting is strongly recommended. At the very least heavy, abrasion resistant jacket of nylon, leather or vinyl and full length pants must be worn.
• Long hair must remain inside helmet. A balaclava or headsock is strongly suggested to prevent it from extending outside of the helmet edges. Red flag will be thrown for flying hair.
• Collar type neck braces designed for motorsports are mandatory.
• Shoes must be high top design, leather or canvas, feet must be fully enclosed, socks are required.
• Abrasion resistant kevlar gloves are highly recommended. Heavy gloves of abrasion resistant material are mandatory.
• It is recommended that all competitors have a fire extinguisher or large water spray bottle in their pit area.

• An air filter is required and must be installed in a safe manner. Air Filter may not be used as a ram air device and must filter from all areas as raced. No open areas are allowed. Filter adapter to carburetor may not be funneled or tapered. Adapter may have a rolled edge not to exceed .250" from top. Maximum thickness of adapter from carburetor mating area to top of adapter is .250", top of adapter must be flat. One gasket may be used with a maximum .075" thickness. Adapter may not be run without air filter.

• May be removed in their entirety. Governor shaft in block or side cover may be broken off or removed and plugged.

• New style recoil started may be left intact. If new style recoil is removed, starter cup must be removed. Old style recoil must be removed. Use of external (not attached to motor) electric starters are allowed.

• Header may not enter into exhaust port so as to alter port configuration. Pipe must be of fixed configuration, no "slippy pipe" designs. No extra tubes to header or extra holes allowed other than heat sensor probes. Bolts must be tight and silencer must be attached so as not to allow leakage through the attachment joint or block to pipe surfaces. Circular loop, bugle/oval shaped, exhaust headers are not allowed. Straight or curve down exhaust headers are allowed. 60° maximum bend. Loss of exhaust system during competition will result in a DNF for that run only.

Box stock means right out of the factory box and NO MODIFICATIONS are allowed. If it does not say you can do it in these rules, then you cannot. All motors are to remain box stock with the exception of what has been stated in these rules. These rules will be strictly enforced for the sake of fair competition.

• An air filter is required and must be installed in a safe manner. Air Filter may not be used as a ram air device and must filter from all areas as raced. No open areas are allowed. Filter adapter to carburetor may not be funneled or tapered. Adapter may have a rolled edge not to exceed .250" from top. Maximum thickness of adapter from carburetor mating area to top of adapter is .250", top of adapter must be flat. One gasket may be used with a maximum .075" thickness. Adapter may not be run without air filter.

• Must be as produced with no alterations or reworking. Block repairs from broken rods or cracked lifter area etc. are permitted providing that repair does not constitute a functional modification of the original block. Blocks may be clearanced on the bottom of the cylinder to provide clearance for all approved connecting rods (see connecting rod section for list of approved rods). Block may NOT be machined on intake or exhaust port gasket mating surface. No bushings are allowed except as listed in this engine section. A DU bearing may be installed in a conventional block on the flywheel side. An extra 1/8" oil hole may be drilled on the flywheel side at the crankshaft bushing of the block to aid in crankshaft oiling. Sleeving of the cylinder block is permitted. Regular ferrous sleeves only, no coatings or plating allowed. The repair of one coil mounting post is allowed as long as the remaining post is unaltered. Lifter bore welding for reinforcement or breakage is allowed. Use of a bushing guide to reinforce the lifter bore area is allowed. Chamfering the bottom of the lifter bore is allowed for clearance purposes only. Chamfer to be 45 degrees and a maximum width of .040". Intake port is subject to .880" no-go gage. Exhaust port is measured with a 1.005" no-go gage. Material cannot be added to ports. No grinding is allowed under valve seats. No holes in ports, if port is pin-punched, resulting risers may not prevent insertion of no-go gage.

• Must be unaltered from factory and functional. Foam and original grommet must be in place. Two gaskets are allowed.

• Any bolt utilized to attach sheetmetal and shrouding may be replaced with a larger diameter with the exception of the sheetmetal held in place with head bolts. Any other bolt may be replaced with the exception of Rod and Head bolts as long as the replacements are the same diameter. See connecting rod section for more clarification. Any stock head bolt may be used; all eight bolts must be present. Factory headbolts with stud extensions on top are permitted.

• Stock cylinder bore is 2.5625". Maximum over bore allowed is .040". Angle boring or machining of grooves or patterns in the bore is prohibited. Stock stroke is 2.4370" +/-.010 for wear, stroke is checked from BDC to TDC. Minimum crankshaft diameter is .990".

• Only stock factory camshaft with original alignment is allowed. Slight grinding allowed for clearance when using approved after market connecting rods.
• Camshaft profile limits measured at zero valve lash:

• Only stock factory camshaft with original alignment is allowed. Slight grinding allowed for clearance when using approved after market connecting rods.

• Stock Briggs & Stratton 5HP, As cast, Raptor II rod and dipper or old style rod with after market dipper is legal. Must be as cast. The following approved after market rods and their respective manufacturer's original connecting rod bolts and/or nuts are allowed for increased engine durability.
• Horstman PN's 4951, 4981
• Holoway PN HR-3.875
• Burris PN's BMC-25400, -26500
• A.R.C. 6350
• No lightening is allowed. Slight grinding allowed on backside of rod for camshaft or lifter clearance.
• Rod length 3.1283" +/-.005"

• Stock 5HP head as shipped from Briggs and Stratton. Machining of gasket surface for sealing purposes and head bolt bosses for flatness is allowed. No other machining is allowed. Minimum head gasket thickness .043", no sealer allowed. Three internal cylinder head surface measurements as measured from the gasket surface to area above piston .011", .408"in spark plug area, .300" in area above valves. Carbon buildup that cannot be cleaned with a dry cloth is considered part of head surface.

• Stock factory crankshaft only. No lightening, polishing or addition of metal allowed. Hardening is allowed to reduce journal wear. Crankshaft may be clearanced to a minimum of .775" to allow easier removal of the bearing. The power takeoff journal of a sleve style bearing crank may be machined to allow its use in a ball bearing style block. Offset cranks are illegal.

• The piston may not protrude more than .015" above deck surface at TDC.

• Stock 5HP only. No painting or coating. No machining. Chipped fins due to poor casting acceptable, completely broken fins are not. Minimum weight 6 lbs. Any screen or guard allowed that fully covers the flywheel. Screen must be bolted to blower housing.

• May be removed in their entirety. Governor shaft in block or side cover may be broken off or removed and plugged.

• Briggs & Stratton factory stock coils only. Must be used in unaltered form, no slotting of mounting holes or modifications to mounting bolts are allowed. Coil air vane must remain intact and unaltered, coil must retard. Plug wire resistance 2000 ohm minimum, 5000 ohm maximum. New style Briggs composite ignition allowed, there must be resistance to ground from the plug wire. Plug wire connector must be stock factory type, rubber boot is legal.

The following pistons are approved for use. The following approved after market pistons are allowed for increased engine durability.

• Briggs & Stratton 5HP stock factory production
• Wiseco PN 1993P - Top may be machined to .937" minimum from top of wrist pin hole.
• Burris PN BMC 258

Measurement from piston top to wrist pin hole is .937" minimum. Minimum length 1.869". Pin hole may not be relocated or altered. Deck above top ring may not be altered, no machining on piston except as noted above. Pin can not be modified, max ID .290", min OD .490".

All 3 piston rings must be used. Top ring, if beveled, may have either a beveled or chamfered inner face or two beveled or chamfered areas on outside face, must remain as manufactured. Two top rings minimum width .105". Second ring may only have an external circumference relief area. Oil ring minimum width .085". Groove with .083" min width, and all 6 oil relief slots must be present. Ends of rings must remain flat. Ring end gaps cannot exceed .500". Rings must conform to factory specifications, stock configuration and be Briggs & Stratton factory approved parts.

• Tank may be altered for tire clearance. Tank repair kit may be used in pickup cup. Gas cap must be stock type with single vent hole and stock gasket and NO modifications allowed. No overflow tubes or cap splash shields.

• Shrouds and covers on engine must be intact and factory stock with NO modifications. Fixed screen may be added to shroud cool air intake area.

• New style recoil started may be left intact. If new style recoil is removed, starter cup must be removed. Old style recoil must be removed. Use of external (not attached to motor) electric starters are allowed.

• Stock valves only. No industrial stellite valves allowed. One angle only on seats and valves. Intake angle 30 , exhaust angle 45 . Minimum intake valve diameter 1.115", intake seat 1.004 minimum diameter. Exhaust valve minimum diameter .990", minimum seat diameter .880". No polishing, knife edging, lightening or refacing allowed. No material may be removed from valve stem, i.e. no linear grooves, or crosshatching etc. Stock Briggs & Stratton valve seats must be used and can be replaced. Stock specification and Briggs & Stratton valve guides allowed. Stacking of stock guides is allowed.

• Stock Briggs & Stratton valve springs and keepers only. Max. Intake spring length 1.240" with .087" wire size. Max. Exhaust spring length is 1.410" with min. .088 wire size. Exhaust spring must be used on exhaust valve and may be used on intake if desired. Springs must remain unaltered with the exception of metal removal from top of spring to allow spring to pass 1.410" min length measurement. One Briggs & Stratton part number 23184 upper retainer may be used on each spring in unaltered form. Maximum lip thickness .058". No extended or adjustable lifters allowed. Lifter head must be .982" min. diameter. Back facing of upper surface of valve chamber to stabilize valve spring retainers and to prevent spring bind is legal.

• Header may not enter into exhaust port so as to alter port configuration. Pipe must be of fixed configuration, no "slippy pipe" designs. No extra tubes to header or extra holes allowed other than heat sensor probes. Bolts must be tight and silencer must be attached so as not to allow leakage through the attachment joint or block to pipe surfaces. Circular loop, bugle/oval shaped, exhaust headers are not allowed. Straight or curve down exhaust headers are allowed. 60 maximum bend. Loss of exhaust system during competition will result in a DNF for that run only.

• If it does not say you can do it in these rules, then you cannot. All motors are to remain stock with the exception of what has been stated in these rules. These rules will be strictly enforced for the sake of fair competition.

• An RLV or equivalent two hole air intake silencer (air box) is required. Baffle tubes must not exceed .905" in diameter and must have a minimum of 3.74" length, a .200" drain hole is allowed. Approved silencer length is 10.63" +/-.40", silencer circumference is 17.32" +/-.80". Filter cup may be used with the silencer providing it is attached in a manner that only allows air to enter the engine induction system through the silencer openings. Air box tubes must extend into the filter cup above the floor level of the cup making a ridge perceptible upon inspection. Filter cup must not be velocity stack shaped or act as a ram tube. Air box silencer carburetor adapter and filter cup must conform to dimensions in "Filter Cup and Silencer Adapter Diagram" on page 12.

• External modifications that do not enhance performance are allowed. Pulse pipe may be relocated to front of motor for reversed cylinder. Hole not in use must be plugged. Internal diameter of pulse pipe may not exceed .128".

• Maximum bore allowed is 2.085", Maximum stroke is 1.816"

• Must be Walbro WB3. Captive and non-captive diaphragms are allowed. Inlet springs can be shimmed. Fuel can only pass through stock metering orifices. No other means of getting fuel into the engine is allowable. Inlet spring may be run in either position. Circuit plate and inlet screens must be intact. Filtering devices to protect metering diaphragm are legal. No depression of diaphragm is allowed. No throttle shaft machining, o-ring seals are allowed. Funneling of brass inlet is illegal. Minimum length of inlet tract from carburetor bore mounting surface to cylinder bore diameter is 2.600", maximum 2.800" not including gasket. Fuel pump must be of original manufacture with the carburetor. Teflon or rubber diaphragm allowed. Phenolic spacer must have straight bore 1.000" minimum, 1.050" maximum diameter. Aluminum carburetor mounting plate must have straight bore of 1.000" minimum, 1.035" maximum. Carburetor must conform to "Carburetor Dimensions" diagram on page 13.

• Rod must be original manufacture and stock appearing. Shot peening allowed. No grinding or polishing allowed. Approved part numbers are Yamaha 7F6-11651-01, 50W-11651-00 and 7F6-11651-02. If rod is located at the top it shall have two or more spacers or bearings at the top. Spacers can be made of aluminum, brass or steel. The bottom of the rod must have a solid bearing and no spacers. If bottom locating rod is used it must have a solid lower bearing and two spacers, one for each side. Top of rod can have a cage bearing or loose needles. If loose needles are used thrust washers are permitted. Original and new style crank pins are permissible. Original stepped and plugged pin must have a .400" minimum I.D. after steel plug removal. Steel plugs must be drillable and removable by competitor for tech inspection. New style non-stepped pins with no plugs are permissible, maximum I.D. .425", minimum I.D. .390".

• No matching of cylinder head or cylinder liner for installation of a sealing device unless it is stock equipment for the KT100s engine. Minimum combustion chamber volume is 11cc's measured to top of spark plug hole with piston at TDC. Cylinder must be stock and manufactured and marked by Yamaha.

• Stock Yamaha crankshaft only. Shot peening and polishing allowed. Maximum O.D. 3.435", minimum O.D. 3.410". Concentric bushings may be added to repair worn crankshafts. Removal of material in bearing recess area is allowed for proper clearance of bearings. Material removal is only allowed for bearing clearances, not for lightening or balancing. Crankshaft must conform to dimensions in "Cluster Diagram" on page 14.

• Exhaust, Intake and Transfer ports must be in as cast condition except at the junction of the cast iron sleeve and aluminum jacket. Grinding is allowed to remove casting irregularities at the junction. Port edges cannot be chamfered. Roof angle of transfer ports cannot be altered. Grinding of ports to change height width or angle is not allowed. Changing the size or shape of passages from cylinder base to port is illegal. Matching of cases to port passages, shot peening, sandblasting, glass beading, media blasting are not permissible. Aluminum may be blended in the inlet track behind the carburetor and exhaust outlet areas only. Due to manufacturing procedures some engines may have slightly broken port edges. When this exists it is uniform on all port edges. It diminishes with cylinder overbore and cannot exist if the bore size is 2.065" or larger.
• New style cylinder barrels must be identified by markings on two bosses between the bottom and first cooling fins. One will have "787" and the other will have "Y3" or "Y4" cast in. No grinding is allowed on the new style cast iron portion of the cylinder.
• Old style cylinder barrels may have the cast iron portion of one exhaust port ground to bring the exhaust port measurements closer to specification. The port must be ground a minimum of 90 degrees to the cylinder wall, no chamfering allowed. The other exhaust port must be left unaltered. When the cylinder has been ground it must be marked with an "X" or arrow on top of the cylinder next to the stud above the port altered.
• Port must conform to dimensions in "Cluster Diagram" on page 14.

• The piston must be stock appearing and an approved single ring design with manufacturers name cast inside. Approved pistons are, Yamaha, Burris (1-dyke ring, 1 thin ring), Wiseco, Vinart and RKE-787 K.S.I. Bottom of piston must be 90 degrees to the sides. The transfer area must be as cast. Piston must be domed design. A .030" break is allowed on skirt area only. Ferrous material rings only. Wrist pin tapering is not allowed, stock type wrist pins only. Minimum length 1.565", minimum O.D. .550", maximum O.D. .552", minimum I.D. .400". No coatings allowed on pistons.
• Piston must conform to dimensions in "Cluster Diagram" on page 14.

• Modification to change ignition timing is not allowed. Right hand flywheel has machined side out. Left hand has cast side out. Taper bore flywheels have one keyway and the cast side is out. Minimum flywheel diameter 2.350", minimum width .817", 3 bosses, minimum thickness .950", minimum length .750". Two thread holes for ruler must be present.

• Head gasket may be copper or aluminum and must be OEM or exact copy in all dimensions. Maximum O.D. is 2.580"

• Acceptable old style ignitions are Yamaha part numbers 7F6-85551-50 and 7F6-8551-00. New style approved part numbers are Yamaha 7F6-8551-01, 7F6-8551-51, 7F6-85510-03-00. PRD TCI and Atom TCI ignitions are allowed. Ignition must be of original manufacture. Ignition keys must fill slots in crankshaft and flywheel; minimum key width is .115". Alteration of coil position is not permitted. Coil damage may be repaired with silicone or epoxy, ignition bearing may be removed.

• 4.14) If it does not say you can do it in these rules, then you cannot. All motors are to remain stock with the exception of what has been stated in these rules. These rules will be strictly enforced for the sake of fair competition.