This engine is to be run as received from the manufacturer (no modifications of any kind). In order to assure that no modifications are performed, the side cover of the engine is sealed. The side cover seal is required in order for the participant to be allowed to race. No tampering of any kind is allowed. The following specifications are to aid the tech personnel in determining whether the engine has been altered from when received from the manufacturer. The seals are not to be reused. In no way do these specifications constitute a need for additional blue printing. Any other method of determining the legality of the engine is OK. After an engine is rebuilt it must be rechecked and resealed by an authorized, bonded, service center. Most items are stock, unaltered parts from Briggs and Stratton. Most parts can be compared to known parts.

712.2.1 Zama .820 Carburetor with butterfly throttle assembly. Venturi .820 no-go. Carb must be stock appearing with single pumper stack of original style on carburetor.

712.2.2 Inspect carburetor for "as cast" venturi surface

712.2.3 Inspect dump tube for original  installation.

712.2.4 Check for additional holes in carburetor

712.2.5 Inspect manifold for angle cuts and offset bolt patterns

712.2.6 Manifold bore, block end .900 no-go, carb end 1.000 no-go, 1.670 to 1.680 long

712.2.7 Air filter adapter to measure less than 1.00" long, taper to 1.070 small inside diameter, no radius allowed. Inspect air filter as per stock 5hp rules.

712.3.1 Robertson Torque Tube #BW 1675 only, 1.045 I.D., Straight, no tapering, installed so the header is angled away from the carburetor. Header length shall not exceed 16.34" long, with or without muffler. R.V.L. muffler #4103.

712.4.1 Factory head only. Spark plug non-tech

712.4.2 Head to have a .005 to .015 deep, .640 max width slot for the piston top clearance.

712.4.3 Combustion chamber as cast from Briggs and Stratton..

712.4.4 Spark plug area to check .385 minimum depth.

712.4.5 Factory supplied head bolts only.

712.4.6 Inspect deck for reworking of eyebrow area.

712.4.7 Single plane machining of deck is permitted. Deck may not be surfaced below top of valve seats.

712.5.1 Factory supplied cover only

712.6.1 Stock Briggs valves only, any springs and retainers. Back facing of the upper valve spring allowed.

712.7.1 Inspect cover for stock

712.7.2 No air vane

712.7.3 Inspect for Briggs and Stratton #491922 fuel pump.

712.7.4 Only one pump is allowed

712.8.1 Check for stock, straight  key

712.8.2 Check for stock 3hp Briggs and Stratton #296884  flywheel.

712.8.3 Check coil for Briggs and Stratton #496914, 3000 ohms max. 

712.8.4 Supplied spark plug connector

712.9.1 Porting as received, no additional porting allowed

712.9.2 Carb inlet side .900 no go

712.9.3 Exhaust inlet side 1.025 no go

712.10 Valve Seat Diameters

712.10.1 Tech for unaltered stock intake seat, single 30 deg. angle, 1.005 ID no-go

712.10.2 Tech for unaltered stock exhaust seat, single 45 deg. angle, .880 ID no-go

712.11.1 Max lift both intake and exhaust is .255

712.11.2 Intake at .100 lift on opening side, before 2 degrees ATDC

712.11.3 Intake at .100 lift on closing side, after 26 degrees ABDC

712.11.4 Exhaust at .100 lift on opening side, before 40 degrees BBDC

712.11.5 Exhaust at .100 lift on closing side, after 5 degrees BTDC

712.12 Inspect Lifters

712.12.1 Check lifters for alterations or re-working per 5 HP rules 701.31

712.13.1 Any stock length (3.875), Super Stock Legal, rod allowed per 705.6 rules.

712.13.2 Inspect for Wiseco Super Stock or Briggs Raptor III Piston

712.13.3 Inspect for Briggs 5 HP or Total Seal Rings    

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