JUNIOR II Age 12 to 15 years –300 lbs. Raptor - Methanol only - Approved engine: Briggs &
Stratton stock Raptor 5hp only, with .575 inch maximum intake restrictor (Gold plate), Slicks only

STOCK Age 16 years & up - 350 lbs. - Methanol only - Approved engine: Briggs & Stratton stock Raptor 5hp
only, slicks only

EMOD 14 years & up - 350 lbs. - Methanol only - Approved engine: Briggs & Stratton stock Raptor 5hp
Only, slicks only

STOCK ANIMAL Age 16 years & up – 350 lbs. - Methanol only - Approved engine: Briggs & Stratton stock
Animal 5.5hp only, slicks only

BRIGGS OPEN RAPTOR Age 18 years & up – 350 lbs. Raptor - Methanol only - Approved engine: Briggs & Stratton 5hp Raptor. Any carburetor allowed. Auxiliary vacuum fuel pump, pulsed from the intake, is permitted. Treaded tires permitted

BRIGGS OPEN ANIMAL Age 18 years & up – 350 lbs. - Methanol only – Approved engine: Briggs & Stratton 5.5hp Animal. Any carburetor allowed. Auxiliary vacuum fuel pump, pulsed from the intake, is permitted. Treaded tires permitted
 

Flags
Green Flag
The race track is clear for racing.

Yellow Flag
There is a need for caution. There is something in the track ahead and you should proceed with caution. If
the flag is waving, there is a problem in that corner. No passing will be allowed in the corner when a
waving yellow flag is displayed. When the yellow flag is displayed at the starter's stand or by the Race
Director, this is a full course yellow. Slow down. No passing until the green flag is displayed again. Note that all
 karts involved in an incident causing a red or yellow flag will be placed at rear of field. If you cause 3 yellow flags, you will be black flagged.

White Flag
One lap to go in the race. White flag is not mandatory.

Checkered Flag
The race is finished. Slow to a moderate pace for exiting the track. Proceed slowly to the post-tech area.
However, the checkered flag may be thrown in conjunction with red or yellow flags, resulting in finish
being determined by last completed scored lap. Racing back to red / yellow flags in conjunction with
checkered flag is not permitted.

Red Flag
The race has been temporarily halted. Slow to a safe stop, drivers shall proceed safely to the starting grid
under direction of the corner workers and flagman.
Restarts will be in the same order as the last completed and scored green flag lap prior to the red flag.
Any driver causing a red flag may be subject to not restarting or disqualification, as determined by the
race director. Note that all karts involved in an incident causing a red or yellow flag will be placed at rear of field.

Black Flag
Racing is not a contact sport, although it is understood some inadvertent contact will occur. Intentional and
avoidable bumping, nerfing, pushing, etc., will be grounds for disqualification. You will be warned only
once with a rolled black flag. A second instance will result in a waved full, black flag.
Rolled & pointed: A warning about driver conduct.

Waved Black Flag: You must exit the track immediately. You have been disqualified for a driving
infraction. If a participant ignores the black flag along with his/her number being displayed by the flagman,
that person will be disqualified for that day in that class.

Personal Safety Equipment
A. Head Gear
1. Full-face helmets designed for competitive motorsports. Helmet must be available at pre-tech inspection. Helmets must
be secured with a strap. Failure to do so will result in disqualification. A full visor or goggles is mandatory.

B. Neck Braces
1. Collar-type, unaltered neck braces designed for motorsports use are mandatory in all classes. Loss of neck brace during an event will cause a black flag. He must immediately proceed to the pits and may replace the missing neck brace and then return to the race or practice session.

C. Driver Apparel
1. Drivers are required to wear long sleeve shirts minumin, and full length pants. Gloves, socks, and shoes are mandatory. Nomex apparel is recommended.
2. Loose clothing, bandanas, scarves, hoods, loose belts, etc. are not allowed.
3. The use of flak jackets, or other chest protection devices is strongly recommended in all classes.
4. All personal safety equipment is subject to, and shall be available for, pre-tech inspection.

Kart Requirements
1: Rear bumber required
2: Numbers must be visible on right front and rear of kart
3: All weights must be secured to karts. This means bolted down. No ty-raps.
4: Nose and side panels are required

Section 4 - Four-cycle engine specs

A- Four-cycle engine specific technical inspection data (Junior 1, Junior 2, Stock)
.
Engine Specific Tech Sheet for: Briggs & Stratton 5hp Junior1, Junior2, Stock Raptor
Description: Single cylinder, two valve, four-cycle
Displacement: 13.017 cubic inches maximum
Cylinder head requirements: Machining permitted on the gasket mating surface and the top of the post
bosses only. Welding on the cylinder head is prohibited. Helicoil repair of spark plug threads in original
position permitted, no protrusion into combustion chamber allowed. Bolt hole diameters .348 inch
maximum. Combustion chamber depths: piston area .011 inch minimum, spark plug area .408 inch
minimum, valve area .300 inch minimum. Any head gasket, not made of aluminum or copper, in stock
configuration and .043 inch minimum thickness midway between bolt holes is permitted. Gasket sealer of
any type is prohibited. Eight stock head bolts required.
Bore and stroke: 2.6025 inch maximum bore, 2.437+.007" or - .010" stroke. Protrusion of the piston
above the top of the cylinder deck .005 inch maximum parallel and inline with the wrist pin
Carburetor requirements: Stock Briggs & Stratton 5hp carburetor only. Pressurized fuel delivery
systems are prohibited. Any means of providing fuel or air flow not originally intended by the manufacturer
is strictly prohibited. No welding to carburetor body or any component except outside end of mixture screw
is permitted. Filter adapter top surface must be flat and .250 inch maximum thickness from mounting face.
Inside diameter of adapter may be radiused .250 inch maximum. No more than one filter adapter gasket.
may be used, thickness .075 inch maximum. One or two carburetor mounting flange gaskets may be used
with no sealer of any type. Throttle shaft washer and rubber seal must be in place and stock
configuration. Throttle shaft leading edge .040 inch minimum, trailing edge .086 inch maximum, flat on
back side .030 min. depth. Butterfly must be unaltered stock with .059 inch minimum thickness at throttle
shaft mating location. Butterfly screw must be unaltered stock, .322 inch minimum length. Except for
outside end, needle screw must be unaltered stock with o-ring and washer present. Jet must have stock
recess on backside with no funneling of hole allowed. Main metering hole diameter .062 inch maximum.
Idle hole diameter .028 inch maximum. Air horn diameter 1.011 inch maximum. Recess at flange end
must be as cast, .726 inch maximum diameter. Carburetor bore, from flange end recess to intersection of air
horn diameter, .695 inch maximum diameter - no attempts to modify fuel/air flow permitted (rifling,
dimpling, protrusions, etc. not permitted). Diaphragm cover plate may be faced for proper sealing.
Aftermarket diaphragm of stock configuration permitted. No sealing agents permitted on diaphragm side of
cover plate gasket. Spring and cup must be unaltered stock. Long fuel pickup tube may not be brass.
Short tube inside diameter .066 inch maximum. Breather tube must be removed. Any stock, single hole,
domed Briggs & Stratton fuel tank cap is permitted including those with integral splash shields.
Valve train: Stock, unaltered breather valve only. Two gaskets permitted. Grommet and internal foam
must be in place. Stock, unaltered, single angle valves only. Length of flat from seating surface to end of
valve .035 inch minimum. Intake valve angle 30˜+/-1˜, 1.115 inch minimum head diameter. Exhaust
valve 45˜+/-1˜, .990 inch minimum head diameter. Stock valve springs and lower retainers required.
Springs may be machined to meet length requirements. One stock upper retainer may be used on either valve, .058 inch maximum lip thickness Both upper valve chamber surfaces may be spot faced for valve spring stabilization. Depth and geometry of spot face non-tech. Stock, single angle valve seats required. Valve seat height to cam centerline 5.740 inch minimum, 5.775 inch maximum. Valve seat may not protrude above cylinder deck surface. Valve seats must meet stock specs
and may be replaced. May be pin punched in eight spots to tighten seat. They must be one angle 30 degrees
intake and 45 degrees exhaust. Intake seat inside diameter is 1.004 max NO-GO, with thickness of .215"
max and .199" min. Exhaust seat inside diameter is .880" max, with thickness of .215" max and .199" min.
Ignition system: Stock, unaltered coil and coil air vane required. Stock, unaltered plug connector
required. Any means to alter position of coil is prohibited. Stock, unaltered 5hp flywheel or billet aluminum matching stock specs (ARC6620). Flywheel coating of any type is prohibited. Revolving or adjustable flywheel screens are prohibited.
Piston requirements: Stock Briggs & Stratton piston Mandatory. Length from top of piston to top of
wrist pin bore .937 inch minimum. piston length is 1.671". Wrist pin outside diameter .490 inch maximum,
inside diameter .291 inch maximum, length 1.732 inch + or - .005". Wrist pin must be unaltered as shipped
from B&S. Cool bore engines may run a Wiseco 1978 piston due to availability of B&S chromed pistons.
Raptor III Rings Specs: Rings must be of Stock configuration and may be lapped with end gap cut. Rings
must be in one piece when removed from piston, with the exception of Raptor III oil ring, however all
pieces must still be present in ring land. Top two rings .090" min width. Top two rings may not exceed ring
land thickness of .058" + or - .005". The step in second ring is .035" min. Oil ring min width is .070", ring
grove must be present. Oil ring Thickness is .100" + or - .005".
Connecting rod requirements: Any commercially or Stock B&S available aluminum connecting rod and
oil dipper is permitted. No .020" undersized rods allowed. Length from bottom of wrist pin bore to top of
crankshaft journal bore 3.120 inch minimum, 3.1333 inch maximum. Connecting rod bolts steel 1/4" only.
Crankshaft requirements: Stock crankshaft required. Machining, polishing, addition of material or
otherwise altering of counterweights is prohibited. Stock timing gear in stock configuration required.
Connecting rod journal diameter .990 inch minimum. Crankshaft journals may be clearanced to .775 inch
minimum diameter to facilitate bearing removal. Thermal treatment of crankshaft is permitted.
Crankcase Side-Cover: Must be stock as supplied from B&S. May be pin punched to secure gasket. May
use up to three gaskets of stock configuration.
Camshaft requirements: Camshaft base circle diameter .770 inch maximum. Ground cams are allowed
but must retain stock configuration. Cams may be center drilled for grinding lobe face. Titanium lifters are
prohibited. Lifter head diameter .982 inch minimum, 1.005 inch maximum; length 1.606 inch maximum.
Camshaft profile limits
Exhaust Lift & Degrees--------------- Intake Lift & Degrees
.050--- 38 °BBDC to 33 °BBDC .050----- 7 °BTDC to 0 °TDC
.100--- 21 °BBDC to 16 °BBDC .100--- 10 °ATDC to 17 °ATDC
.150---- 2 °BBDC to 3 °ABDC .150--- 29 °ATDC to 36 °ATDC
.200--- 21 °ABDC to 31 °ABDC .200--- 55 °ATDC to 64 °ATDC
Max-- .233 inch maximum---------- .233 inch maximum
.200--- 76 °BTDC to 65 °BTDC .200---- 43 °BBDC to 33 °BBDC
.150--- 48 °BTDC to 40 °BTDC .150---- 13 °BBDC to 6 °BBDC
.100--- 28 °BTDC to 21 °BTDC .100----- 6 °ABDC to 13 °ABDC
.050--- 10 °BTDC to 4 °BTDC .050----- 23 °ABDC to 31 °ABDC
EZ Spin start 45 ° to 60 ° ABDC
EZ Spin lift base .013 inch minimum, .019 inch maximum, 30 ° minimum duration, .001 inch maximum
drop during duration.
Block requirements: Side cover must be stock. Stub for governor may be removed and hole plugged.
Gasket mounting surface of side cover and block may be pin punched. A maximum of three stock
configuration side cover gaskets are permitted. Block must be unaltered stock with the following
exceptions: The lifter bores may be countersunk to provide lifter head fillet radius clearance. Any means to
raise the bottom of the lifter bore boss is prohibited. Welding to the block shall be for damage repair or
lifter bore reinforcement only and may not constitute a functional modification. The cylinder deck may be
machined, not to extend into the rear fin. Carburetor and exhaust pipe mounting surfaces must be unaltered
stock. Alterations to inside surfaces of intake and exhaust ports are allowed so long as the intake port will
not accept an .880 inch diameter No-Go plug gauge and the exhaust port will not accept a 1.005 inch
diameter No-Go plug gauge. No addition of material is allowed. No additional holes may exist in the intake
and/or exhaust ports. No alterations on the underside of the valve seats are allowed. Cylinder sleeve, if
present, shall be ferrous and uncoated. Welding of block to repair broken rod damage is permitted as long
as it does not constitute a functional modification. Bottom exhaust hole may also be welded (cannot
protrude into exhaust port). Extra oil hole may be drilled on flywheel side of block to help lubricate
crankshaft 1/8" in diameter.

B - Four-cycle engine specific technical inspection data ( EMOD)
Engine Specific Tech Sheet for: Briggs & Stratton 5hp EMOD Raptor
Description: Single cylinder, two valve, four-cycle
Displacement: 13.017 cubic inches maximum
Cylinder head requirements: Machining permitted on the gasket mating surface and the top of the post
bosses only. Welding on the cylinder head is prohibited. Helicoil repair of spark plug threads in original
position permitted, no protrusion into combustion chamber allowed. Bolt hole diameters .348 inch
maximum. Combustion chamber depths: piston area .011 inch minimum, spark plug area .408 inch
minimum, valve area .300 inch minimum. Any head gasket, not made of aluminum or copper, in stock
configuration and .043 inch minimum thickness midway between bolt holes is permitted. Gasket sealer of
any type is prohibited. Eight stock head bolts required.
Bore and stroke: 2.6025 inch maximum bore, 2.437+.007" or - .010" stroke. Protrusion of the piston
above the top of the cylinder deck .005 inch maximum parallel and inline with the wrist pin
Carburetor requirements: Stock Briggs & Stratton 5hp carburetor only. Pressurized fuel delivery
systems are prohibited. Any means of providing fuel or air flow not originally intended by the manufacturer
is strictly prohibited. No welding to carburetor body or any component except outside end of mixture screw
is permitted. Filter adapter top surface must be flat and .250 inch maximum thickness from mounting face.
Inside diameter of adapter may be radiused .250 inch maximum. No more than one filter adapter gasket.
may be used, thickness .075 inch maximum. One or two carburetor mounting flange gaskets may be used
with no sealer of any type. Swirl non-tech. Throttle shaft washer and rubber seal must be in place and stock
configuration. Throttle shaft leading edge .040 inch minimum, trailing edge .086 inch maximum, flat on
back side .030 min. depth. Butterfly must be unaltered stock with .059 inch minimum thickness at throttle
shaft mating location. Butterfly screw must be unaltered stock, .322 inch minimum length. Except for
outside end, needle screw must be unaltered stock with o-ring and washer present. Jet must have stock
recess on backside with no funneling of hole allowed. Main metering hole diameter .062 inch maximum.
Idle hole diameter .028 inch maximum. Air horn diameter 1.011 inch maximum. Recess at flange end
must be as cast, .726 inch maximum diameter. Carburetor bore, from flange end recess to intersection of air
horn diameter, .695 inch maximum diameter - no attempts to modify fuel/air flow permitted (rifling,
dimpling, protrusions, etc. not permitted). Diaphragm cover plate may be faced for proper sealing.
Aftermarket diaphragm of stock configuration permitted. No sealing agents permitted on diaphragm side of
cover plate gasket. Spring and cup must be unaltered stock. Long fuel pickup tube may not be brass.
Short tube inside diameter .066 inch maximum. Breather tube must be removed. Any stock, single hole,
domed Briggs & Stratton fuel tank cap is permitted including those with integral splash shields.
Valve train: Stock, unaltered breather valve only. Two gaskets permitted. Grommet and internal foam
must be in place. Stock, unaltered, single angle valves only. Length of flat from seating surface to end of
valve .035 inch minimum. Intake valve angle 30˜+/-1˜, 1.115 inch minimum head diameter. Exhaust
valve 45˜+/-1˜, .990 inch minimum head diameter. Stock valve springs and lower retainers required.
One stock upper retainer may be used on either valve, .058 inch maximum lip thickness. Stock, single angle valve seats required. Valve seat height to cam centerline 5.740 inch minimum, 5.775 inch maximum. Valve seat may not protrude above cylinder deck surface. Valve seats must meet stock specs and may be replaced. May be pin punched in eight spots to tighten seat. They must be one angle 30 degrees intake and 45 degrees exhaust. Intake seat inside diameter is 1.004 max NO-GO, with thickness of .215" max and .199" min. Exhaust seat inside diameter is .880" max, with thickness of .215" max and .199" min.
Ignition system: Stock, unaltered coil and coil air vane required. Stock, unaltered plug connector
required. Any means to alter position of coil is prohibited. Stock, unaltered 5hp flywheel or billet aluminum matching stock specs (ARC6620). Flywheel coating of any type is prohibited. Revolving or adjustable flywheel screens are prohibited.
Piston requirements: Stock Briggs & Stratton piston Mandatory. Length from top of piston to top of
wrist pin bore .937 inch minimum. piston length is 1.671". Wrist pin outside diameter .490 inch maximum,
inside diameter .291 inch maximum, length 1.732 inch + or - .005". Wrist pin must be unaltered as shipped
from B&S. Cool bore engines may run a Wiseco 1978 piston due to availability of B&S chromed pistons.
Raptor III Rings Specs: Rings must be of Stock configuration and may be lapped with end gap cut. Rings
must be in one piece when removed from piston, with the exception of Raptor III oil ring, however all
pieces must still be present in ring land. Top two rings .090" min width. Top two rings may not exceed ring
land thickness of .058" + or - .005". The step in second ring is .035" min. Oil ring min width is .070", ring
grove must be present. Oil ring Thickness is .100" + or - .005".
Connecting rod requirements: Any commercially or Stock B&S available aluminum connecting rod and
oil dipper is permitted. No .020" undersized rods allowed. Length from bottom of wrist pin bore to top of
crankshaft journal bore 3.120 inch minimum, 3.1333 inch maximum. Connecting rod bolts steel 1/4" only.
Crankshaft requirements: Stock crankshaft required. Machining, polishing, addition of material or
otherwise altering of counterweights is prohibited. Stock timing gear in stock configuration required.
Connecting rod journal diameter .990 inch minimum. Crankshaft journals may be clearanced to .775 inch
minimum diameter to facilitate bearing removal. Thermal treatment of crankshaft is permitted.
Crankcase Side-Cover: Must be stock as supplied from B&S. May be pin punched to secure gasket. May
use up to three gaskets of stock configuration.
Camshaft requirements: Stock camshaft only. Ground cams and aftermarket cams are not allowed. Titanium lifters are prohibited. Lifter head diameter .982 inch minimum, 1.005 inch maximum; length 1.606 inch maximum.
Camshaft profile limits (May be edited at a later date)
Exhaust Lift & Degrees--------------- Intake Lift & Degrees
.050--- 38 °BBDC to 33 °BBDC .050----- 7 °BTDC to 0 °TDC
.100--- 21 °BBDC to 16 °BBDC .100--- 10 °ATDC to 17 °ATDC
.150---- 2 °BBDC to 3 °ABDC .150--- 29 °ATDC to 36 °ATDC
.200--- 21 °ABDC to 31 °ABDC .200--- 55 °ATDC to 64 °ATDC
Max-- .233 inch maximum---------- .233 inch maximum
.200--- 76 °BTDC to 65 °BTDC .200---- 43 °BBDC to 33 °BBDC
.150--- 48 °BTDC to 40 °BTDC .150---- 13 °BBDC to 6 °BBDC
.100--- 28 °BTDC to 21 °BTDC .100----- 6 °ABDC to 13 °ABDC
.050--- 10 °BTDC to 4 °BTDC .050----- 23 °ABDC to 31 °ABDC
EZ Spin start 45 ° to 60 ° ABDC
EZ Spin lift base .013 inch minimum, .019 inch maximum, 30 ° minimum duration, .001 inch maximum
drop during duration.
Block requirements: Side cover must be stock. Stub for governor may be removed and hole plugged.
Gasket mounting surface of side cover and block may be pin punched. A maximum of three stock
configuration side cover gaskets are permitted. Block must be unaltered stock. Welding to the block shall be for damage repair. Carburetor and exhaust pipe mounting surfaces must be unaltered stock. Alterations to inside surfaces of intake and exhaust ports are not allowed. The intake port must not accept an .880 inch diameter No-Go plug gauge and the exhaust port will not accept a 1.005 inch diameter No-Go plug gauge. No addition of material is allowed. No additional holes may exist in the intake
and/or exhaust ports. No alterations on the underside of the valve seats are allowed. Cylinder sleeve, if
present, shall be ferrous and uncoated. Extra oil hole may be drilled on flywheel side of block to help lubricate
crankshaft 1/8" in diameter.

C- Four-cycle engine specific technical inspection data for Briggs and Stratton Animal 5.5 Stock
Description: Single cylinder, two valve, four cycle
Combustion chamber volume: 24 cubic centimeter minimum, with piston at TDC, using prescribed
procedure.
Cylinder head requirements: Must be OEM casting. “Animal” cylinder head part # 558 only. Porting
and/or grinding are not permitted. Depth of head at shallow part is .011" Min. Depth of head at the floor is
.319" Min. Depth to top of valve seat .360" max and .335" min. Head thickness from head gasket surface to
head plate gasket surface is 2.420". Width of combustion chamber at the widest part across the valve seat
area is checked with a 2.640" NO-GO at a depth of .200" in the combustion chamber. Valve seats are one
angle 45 degrees (both). Stock B&S seats only. Intake seat inside diameter is .966" - .972". Exhaust seat
inside diameter is .844" - .850". Intake inlet .918" NO-GO. Exhaust outlet is .980" NO-GO. Stock valve
guides as supplied from factory. Stock replacement guides allowed. Max depth on intake
guide is 1.255" from top of guide to the gasket surface above. Stock head bolts only, must have four. Head
gasket B&S or after market allowed of stock configuration. No copper or aluminum. Min gasket thickness
.049" measured in four places.
Bore and stroke: Stock cylinder bore is 2.690" with an overbore of 2.725" max (approx .035 overbore).
Stroke is 2.204" max.
Carburetor requirements: PZ model 15 Carburetor only. Carb to intake sealer is o-ring only no other
sealer allowed. Choke must be as supplied from factory, but may be fixed in open position. Adapter on fuel
inlet allowed to accommodate 1/4" fuel line. Max throttle bore is .874" as cast. Choke bore 1.149" NO-Go.
Venturi vertical .792"NO-GO, Horizontal .615" NO-GO, for top and bottom of venturi (widest part), and
.602" NO-GO will be for horizontal for the narrowest part of venturi and this NO-GO may not enter slide
area. Air pickup hole Max .061" NO-GO. Min length top edge of slide to deepest part of cut away 1.148".
Must be as stock. Needle jet 1.690" max length and1.680" min length. Taper on needle must remain stock
and will be checked at .500" from the tip of needle and must not be smaller than .070". Any air cleaner
allowed. Must be installed directly to carb. Filter can not create an air ram. Auxiliary fuel pump (pulse
type), pulsed from the upper oil fill hole or intake manifold, is permitted. Stock Intake as supplied from
factory only, no modifications allowed. May be drilled and taped for fuel pump fitting. Manifold length
1.740" min and 1.760" max. Inside I.D. .905" NO-GO max and .885" NO-GO.
Valve train: Stock valve cover only. Factory stock rocker arms and rocker plate only. Ball rocker as stock
from factory. Ball .600 + or - .010" diameter. Push Rods as stock from factory .185" - .190" diameter.
Length 5.638" - 5.656". Cylinder head plate must as stock from factory. Cylinder head plate gasket must be
stock configuration and max thickness of .055". Stock valves only 45 degree angle only (both). Can not be
lightened or polished. Intake valve diameter is 1.055" - 1.065". Depth of dish in valve is .099" - .119". Min
height of combustion chamber to top of valve is .057". Exhaust valve diameter is .935" - .945". Depth of
dish in valve is .084" - .104". Min height of combustion chamber surface to top of valve is .060". Valve
springs stock B&S valve springs and keepers only. Springs must remain unaltered as supplied from B&S.
Max valve spring length .930" with max wire diameter of .103" - .107" measured in three places. Inside
spring diameter is .615" min, and .635" max. Valve spring retainers are as stock from factory with .060" -
.070" thickness. Stock valve lifters only. Lifter head diameter .820" min, .860" max, with a max length of
1.525" and min length of 1.515".
Ignition system: B&S factory stock coils only and must be unaltered.
Flywheel: Only stock B&S flywheel allowed part # 555625 with Plastic fins. No alterations of any type
allowed. Any or no flywheel key allowed. Minimum weight is 4lbs. 8oz.
Piston requirements: Stock unaltered B&S Animal piston only. No machining on piston is allowed.
Wrist pin hole may be honed for clearance. Arrow must point towards flywheel. Min piston length is
1.768". Wrist pin must be as shipped from B&S. Max inside diameter is .414" with outside diameter of
.624"-.626", and a Min length of 1.901".
Rings requirements: Three rings are mandatory. Rings must be as shipped from factory. Top ring must
have chamfer or O must face up. Second ring must have inside chamfer down and O up. Stock oil ring must
be installed with expander. Top two rings Min width is .095" with a thickness of .059" - .064". Oil ring Min
width is .065", ring grove must be present. Oil ring thickness is .098" - .102".
Connecting rod requirements: The use of first and second generation rods are allowed, also the
aftermarket stock rods (ARC, WMS, etc.) are allowed. The new B&S rod bolts are allowed part #555654.
Minor grinding of crankcase to clearance for new style rod bolts allowed. Rod length is 2.419" min, 2.429"
max, measured from bottom of wrist pin hole to top of crank journal.
Crankshaft requirements: Stock crankshaft required. Machining, polishing, addition of material or other
alteration of crankshaft is prohibited. Stock factory timing gear mandatory and must be installed in original
location. Rod journal diameter 1.094" - 1.100".
Camshaft requirements: All profile readings are to be taken with zero valve lash. Lobes may be ground
but must have a Min base circle of .870". Maximum lift, either lobe, is .255 inch, measured at valve with
zero valve lash.
Block requirements: Block must be as produced by B&S. Stub for governor may be
removed and hole plugged. Block must be unaltered stock except machining of the cylinder head mating
surface is permitted. Overbore and installation of ferrous cylinder sleeve allowable. Sleeve must be
installed in stock location and orientation. Welding to the block shall be for rod damage repair only and
may not constitute a functional modification. The repair of one coil post is allowed as long as remaining
post is unaltered. No Knurling of valve guides allowed. Use of steel bore block originally intended for
“Animal” only permissible.
Additional requirements: External surfaces of cylinder heads and blocks may be machined to remove
excess material from mounting bosses, cast-in brackets, etc. that are no longer in use. No external
machining allowed that produce a performance gain. If recoil starter assembly is removed, starter cup must
also be removed and a non-rotating flywheel screen must be installed.
Camshaft Profile Limits:
Intake Lift & Degrees-----------------------------------Exhaust Lift & Degrees
.020"................................ 18 to 13 BTDC .020"...............................61 BBDC to 56 BBDC
.050"...........................0 TDC to 4 ATDC .050"...............................44 BBDC to 40 BBDC
.100"....................16 ATDC to 20 ATDC .100"...............................27 BBDC to 23 BBDC
.150"....................33 ATDC to 37 ATDC .150".................................11 BBDC to 7 BBDC
.175"....................42 ATDC to 46 ATDC .175"...................................1 BBDC to 3 ABDC
.200"....................53 ATDC to 57 ATDC .200"...............................10 ABDC to 14 ABDC
.225"....................67 ATDC to 71 ATDC .225"...............................24 ABDC to 28 ABDC
MAX.............................Max Lift is .257" MAX..........................................Max lift is .257"
.225......................39 BBDC to 35 BBTD .225"...............................78 BTDC to 74 BTDC
.200......................25 BBDC to 21 BBDC .200"...............................64 BTDC to 60 BTDC
.175......................15 BBDC to 11 BBDC .175"...............................53 BTDC to 49 BTDC
.150..........................5 BBDC to 1 BBDC .150"...............................43 BTDC to 39 BTDC
.100......................12 ABDC to 16 ABDC .100"...............................27 BTDC to 23 BTDC
.050......................28 ABDC to 32 ABDC .050".................................10 BTDC to 6 BTDC
.020......................44 ABDC to 49 ABDC .020".................................5 ATDC to 10 ATDC

Section 5- Four-cycle engine specific technical tools
The following tools are used for technical inspections following the race event
Raptor Tools
Intake port…….0.880 Go No-Go
Exhaust port…..1.005 Go No-Go
Bore…………...2.6025 Go No-Go
Carb Inlet……..1.012 Go No-Go
Carb Outlet……0.726 Go No-Go
Intake Seat I.D…1.005 Go No-Go
Exhaust Seat I.D. 0.880 Go No-Go

 

Animal Tools
Intake port…….0.918 Go No-Go
Exhaust port…..0.980 Go No-Go
Bore…………...2.726 Go No-Go
Carb Inlet……..1.149 Go No-Go
Carb Outlet……0.905 Go No-Go
Intake Seat I.D…0.973 Go No-Go
Exhaust Seat I.D. 0.851 Go No-Go

 

 

 

Have a fun and safe 2008 racing season at the 160 Speedway.