Clone and Builder Prepared Class Rules
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Participant ages are determined as of January 1st. BOX STOCK SENIOR* Age 15 years & up 375 lbs. 87 Octane Gas Only Approved engine: BS Project 6.5 OHV only, with Factory Stock exhaust required. Stamped steel drum shoe type clutches only. (Tires EL Maxxis or Local Club Tire Rule) BOX STOCK SR CHAMP* Age 15 years & up 400 lbs. 87 Octane Gas Only - Approved engine: BS Project 6.5 OHV only, with Factory Stock exhaust required. Stamped steel drum shoe type clutches only. (Tires EL Maxxis or Local Club Tire Rule) BOX STOCK JUNIOR 1* Age 8 to 10 years 265 lbs. 87 Octane Gas Only - Approved engine: BS Project 6.5 OHV only, with .500 inch maximum intake restrictor, no steering fairing allowed , maximum nose height 14 inches from ground level to top of nose, and Factory Stock exhaust required. Stamped steel drum shoe type clutches only. (Tires EL Maxxis or Local Club Tire Rule) BOX STOCK JUNIOR 11* Age 10 to 12 years 290 lbs. 87 Octane Gas Only - Approved engine: BS Project 6.5 OHV only, with .550 inch maximum intake restrictor, no steering fairing allowed , maximum nose height 14 inches from ground level to top of nose, and Factory Stock exhaust required. Stamped steel drum shoe type clutches only. (Tires EL Maxxis or Local Club Tire Rule) BOX STOCK JUNIOR 111* Age 12 to 15 years 320 lbs. 87 Octane Gas Only - Approved engine: BS Project 6.5 OHV only, and Factory Stock exhaust required. Stamped steel drum shoe type clutches only. (Tires EL Maxxis or Local Club Tire Rule)
Description: Single cylinder, 2 valve, OHV 4 cycle Important Note: All parts must be Box Stock Project factory production parts unless otherwise specified in this rules manual. No machining or alteration of parts is allowed unless specifically noted. All parts will be subject to a comparison to a know Box Stock part (when performing a comparison check it is recommended to use a + /- .005 tolerance). Engine will be teched as raced. There will also be a $200 claiming rule in place for this engine. Refusing to accept the claimer will result in immediate disqualification of competitor along with forfeiture of any points earned to date in class. Competitor will also not be allowed to compete any longer in that class. Combustion chamber volume: 26.5 cubic centimeter minimum, with piston at TDC, using prescribed procedure. Cylinder Head Requirements: Must be OEM casting only. Porting and / or grinding are not permitted. Valve seats are two angles 45 degrees valve face and 30 degrees top relief. Stock head bolts only, must have four. Head gasket maybe after market, must be of stock configuration. No copper or aluminum gaskets allowed. Stock exhaust system only with no modifications. Any stock configuration gasket allowed no other sealer. Bore and Stroke: Stock cylinder bore is 2.685 max. Stroke is 2.123 + / - .005. Carburetor requirements: Huayi OR RUI*ING model carb only. Carb to intake sealer is gasket only no other sealer allowed. Choke must be as supplied from factory, but may be fixed to stay in open position. Choke bore .810 NO-GO. Venturi .615 NO-GO. Rear carb bore .751 NO-GO. Main fuel jet .028 NO-GO. Stock air cleaner assembly only. Valve Train: Stock valve cover only with any stock configuration gasket, no sealer. Factory stock rocker arms and push rods only. Stock valves only 45 degree angle only both valves, no modifications allowed. Only Box Stock valve springs only. Max wire diameter on spring wire is .0698 with a maximum tension of 10.8 lbs. at a height of .850. Ignition system: Stock Box Stock system only and must be unaltered. Kill switch and low oil sensor may be disabled and removed. Flywheel: Box Stock flywheel only with plastic fins. No alterations of any type allowed. Must also run stock flywheel key. Piston and Rings: Must be unaltered Box Stock only. No machining of piston and rings allowed. Connecting Rod: Stock Box Stock rod only. No machining of any type allowed. Stock rod bolts only. Crankshaft Requirements: Stock Box 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. Crankshaft journal diameter is 1.180- 1.175 min. Camshaft Requirements: Stock as cast camshaft only. Cam lobe base circle diameter .865" -.005/+.010 Duration check for Intake and Exhaust lobes (taken off pushrod). Intake duration of 218.5 degrees at .050 lift/85.5 degrees at .200 lift. Exhaust duration of 221.5 degrees at .050 lift/96.5 degrees at .200 lift. (All checks will allow +2 degrees for wear and gauge variances.)
Max Intake lift on cam .225 taken at the pushrod. Special note. Valve guide wear can give false valve lift readings when checking off the front of the valve spring retainer. It is advised to take readings at several other points around the retainer (back, and both sides) if wear is suspected of giving a false, unfavorable reading. Block Requirements: Block must remain stock as produced. Stub for governor may be removed and hole plugged. No machining of block allowed. Welding to the block shall be for rod damage repair only and may not constitute a functional modification.
Aftermarket air filter adapter allowed (max length of 1.375). Main fuel jet may be drilled to a no-go of .042 inch. Stock emulsion tube must be used and unaltered. Header and Muffler Requirements: Any single stage, one piece header made from .750 O.D. steel tubing allowed with the BS tube style muffler part #89966 or its aftermarket equivalent(ex: rotary power) installed at the end of pipe. The tube style muffler may either be welded or tread fitted to the pipe end. The entire exhaust pipe including the muffler is 14 max length and 10 min length. Claimer Rule: You must finish the race in the box stock class to purchase the winners engine for $200 (minus the clutch/chain guard/throttle kit, header pipe/muffler, air filter adaptor/air filter, top plate & fuel pump).
The Following updates are mandetory changes as of January 1, 2009
Only Burris tire (any compound) can be used, the Box Stock class will have an open clutch rule (drum, disk, or disks) and will also allow any (brand and length) exhaust pipe so long as it has a RVL muffler.
BP (Builder Prepared)* Age 15 years & up 375 lbs. 6.5 OHV GASOLINE ONLY 87-93 octane Approved Engine: 6.5 OHV 196cc clone engine modified only according to BP OHV Engine Spec. Tires are track/series option. ENGINE SPEC SHEET FOR BP 6.5 OHV CLASS: Description: Single cylinder, 2-valve overhead 4-cycle engine. No aftermarket coatings of any type are permitted on any part of the engine. Cylinder Head Requirements: Stock cylinder head only. Machining of gasket surface is allowed. No addition of material in ports or to cylinder head allowed. Valve seats may have two angles, 45° valve face and 30° top relief. Inside diameter of valve seats must be stock. Valve seats must appear stock and must be in stock position and depth. Stock head bolts are required and all four are required. Minimum head gasket thickness is .009. More than one gasket may be used. Cylinder head guide plate for pushrods must remain stock. No other alterations to the stock head are permitted. Bore and Stroke: Stock bore is 2.685 and may be over bored to 2.718 Stroke is 2.123 +/-.005. Connecting Rod: Billet aluminum rods, with or without bearing inserts allowed. No titanium rods allowed. Rod length is a non tech item. Combustion Chamber Volume: 25 cubic centimeter minimum with piston at TDC using procedure posted below. Carburetor/Intake Requirements: Stock Huayi or RUI*ING carb. Venturi .615 NO-GO. Rear carb bore .751 NO-GO. Air Filter adapter of 1.375 max length allowed. No air rams. Pulse-type fuel pump is mandatory. Fuel pump must be pulsed from either the crankcase or the valve cover. Black phenolic carb insulator must be used. Choke assembly may be removed. Jets, air bleed jets, and emulsion tube are non-tech. Throttle shaft, screw, washer, and butterfly must be stock and must be present. Stock intake runner gasket configuration only. One extra gasket may be used with restrictor plates. No other alterations are permitted. Ignition system: Ignition timing is non tech. Stock ignition module only. No modifications of any type allowed. Sparkplug connector must be stock as from factory. Piston Requirements: Must be stock dished piston with no modifications. Oversize Clone or Honda ZOT dished piston is allowed up to .035" oversize. Rings must appear stock and all rings must be installed. Piston may not pop out above cylinder deck. Valve Train: Stock valve-train only in stock configuration except any single valve springs and valve spring shims are allowed. No additional support for rocker studs permitted. Valves must be one angle only, 45°. No polishing, lightening or knife edging of valves (1mm min. margin). Valve length is non-tech. Outside face of valve head may not be below the combustion chamber floor. (i.e. dont sink the valves) Valve cover may be drilled for fuel pump pulse fitting, otherwise, it must remain unaltered. Valve cover gasket is non-tech. Camshaft Requirements: BP spec cam only. Profile check taken at pushrod must match +/- 3° to spec cam. Maximum lift at the pushrod is .246. Minimum lift at the pushrod is .240. Maximum total lift of .260 to be checked at valve spring retainer with zero lash. Special note. Valve guide wear can give false valve lift readings when checking off the front of the valve spring retainer. It is advised to take readings at several other points around the retainer (back, and both sides) if wear is suspected of giving a false, unfavorable reading. Compression release must remain on the cam. Currently available cams that meet spec: Dyno 216, (others that meet spec are ok) BP Cam Degree Profile Checks @ Pushrod
Intake
Exhaust
Block Requirements: Stock Block, as cast and produced with no alterations or modifications other than those specifically permitted. Block head matting surface may be machined, however, no piston pop out is allowed. Blocks may NOT be welded for repairs. No addition of material to block (i.e. welding, jb weld, etc). All bolt bosses in block may be drilled and tapped for repairs or other uses. Additional side cover gaskets as required for crankshaft thrust are permitted. All parts associated with the governor and the low oil sensor may be removed, plugging any associated holes. Flywheel: Approved SFI certified billet aluminum flywheel only. No machining or alteration of any kind allowed. Minimum weight for flywheel is 3.3 lbs. Any timing key or no key at all may be used. A flat washer or spacer may be used, and is recommended, between the flywheel and the nut. Stock pull starter must be used. Current Approved flywheels: ARC 6619, ARC 6618 Header and Muffler Requirements: Header Pipe Length: Minimum 18- Maximum 22. Silencer must be a RLV 91_L type with .1285 no-go hole. Header must be securely wrapped from flange to muffler prior to the race. No other alterations to or from stock components are allowed. No buy out for the BP (Builder Prepared) class, Tech will be enforced and protest cost/conditions are the same as the Stock and Restricted (Briggs) classes.
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Contact:
Mike Hillard (865) 388-4030
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