{AKRA BOX STOCK/6.5 CLONE/2011 RULES with a few Weight Classes added}

AKRA Box Stock/6.5 Clone/2011

CLASSES RUNNING AT KART KNIGHTS
Medium 350 lbs.
Heavy 375 lbs.
Super Heavy 400 lbs

Class Structure

Participant ages are determined as of January 1st.

BOX STOCK SENIOR* Age 15 years & up – 375 lbs. – 87 Octane Gas Only – Approved engine: Any 6.5 BS Clone Style Engine OHV only, with AKRA approved Exhaust System. Stamped steel drum shoe type clutches only. (Series or Local Club Tire Rule) Local clubs to add other weight classes as needed such as light, medium, and super heavy.

BOX STOCK SR CHAMP* Age 15 years & up – 400 lbs. – 87 Octane Gas Only - Approved engine: Any 6.5 BS Clone Style Engine OHV only, with AKRA approved Exhaust System. Stamped steel drum shoe type clutches only. (Series or Local Club Tire Rule)

BOX STOCK JUNIOR 1* Age 8 to 10 years – 265 lbs. – 87 Octane Gas Only - Approved engine Any 6.5 BS Clone Style Engine OHV only, with .500 inch maximum intake restrictor, with AKRA approved Exhaust System. No steering fairing allowed , maximum nose height 14 inches from ground level to top of nose. Stamped steel drum shoe type clutches only. (Series or Local Club Tire Rule)

BOX STOCK JUNIOR 11* Age 10 to 12 years – 290 lbs. – 87 Octane Gas Only - Approved engine: Any 6.5 BS Clone Style Engine OHV only, with .550 inch maximum intake restrictor, with AKRA approved Exhaust System. No steering fairing allowed , maximum nose height 14 inches from ground level to top of nose. Stamped steel drum shoe type clutches only. (Series or Local Club Tire Rule)

BOX STOCK JUNIOR 111* Age 12 to 15 years –320 lbs. – 87 Octane Gas Only - Approved engine: Any 6.5 BS Clone Style Engine OHV only, with AKRA approved Exhaust System. Stamped steel drum shoe type clutches only. (Series or Local Club Tire Rule)


ENGINE SPECIFIC TECH SHEET FOR: BOX STOCK 6.5 OHV 

Description: Single cylinder, 2 valve, OHV 4 cycle
Important Note: All parts must be Box Stock 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 known Box Stock part (when performing a "stock part" 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. Intake seat maximum ID .897” , Exhaust seat maximum ID .862”. Stock head bolts only, must have four. Head gasket/s maybe after market, must be of stock configuration, 2 gaskets permitted with a total minimum thickness of .008” and maximum of .020”. No copper or aluminum gaskets allowed. Any stock configuration exhaust gasket allowed no other sealer.

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. Stock cylinder bore is 2.685" max. Stroke is 2.123" + .010" or - .005". No piston pop-out allowed. Matting surface finish of block and cylinder head is a non tech item, sufacing of both to correct gasket failure and meet cc check allowed. May use 2 side cover gaskets of stock configuration. 

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. Venturi .615” NO-GO. Rear carb bore .751” NO-GO. Main fuel jet .042” NO-GO. Low speed idle jet .019” NO-GO. Stock emulsion tube must be used and unaltered, .066" max ID (no pass through). Throttle shaft - .115” minimum. Butterfly - .037” minimum. Aftermarket air filter adapter allowed (max length of 1.375). 

Valve Train: Stock valve cover only with any stock configuration gasket, no sealer. Factory stock rocker arms 1:1 ratio and push rods only. Stock valves only 45 degree angle only both valves, Intake valve Max OD .985” +/- .005” and Exhaust valve Max OD .948” +/- .005”, no modifications allowed. Only Box Stock valve springs. Max wire diameter on spring wire is .071” with a maximum tension of 10.8 lbs. at a height of .850”. Lash cap on exhaust valve only. Valve stem seal allowed only on Intake valve, maximun lip tickness of .027”. Minimum thickness of Intake retainer .230” , Exhaust retainer .250”. BS lifters only, no modifications allowed.

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(5lbs 4 oz minimum) including plastic fins. No alterations of any type allowed. Maximum ignition timing advance is 18° BTDC when a straight edge placed on the outside of the right-hand coil leg is just touching the right-hand edge of the metal magnet cover of the flywheel. Flywheel key is non-tech.


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”max - 1.168” min.

Camshaft Requirements: Stock camshaft cores only, ez-spin assy must remain as stock. Cam lobe base circle diameter .865" -.005”/+.010” Duration check for Intake and Exhaust lobes (taken off pushrod). Intake duration of 219 degrees at .050 lift/86 degrees at .200 lift. Exhaust duration of 222 degrees at .050” lift/97 degrees at .200” lift(All duration checks on intake and exhaust allow +/- 2 degrees for wear and gauge variances). Max Intake lift on cam .225” – Min .215”lift taken at the pushrod. Max Intake lift at the valve .238” Taken on valve spring retainer with zero lash. Max Exhaust lift on cam .232” – Min .222” lift taken at the pushrod. Max Exhaust Lift at the valve .242” Taken on valve spring retainer with zero lash.

Blower Housing Assembly: pull starter must be present and remain stock. Pull starter may be rotated for a better crank angle.

Header and Muffler Requirements: Any single stage, one piece header made from .750” OD max and .635” ID max. steel tubing allowed, with the RLV Mini B-91 Silencer (Optional 12-1-2010 and mandantory 3-1-2011) installed at the end of pipe. The B-91 Silencer must be tread fitted to the pipe end. The entire exhaust pipe including the muffler is 15” max length and 10” min length. RLV Mini 91 Silencer Requirements: Part # 4117 Overall Length 5.465” minimum – 5.605” maximum. Threaded Nipple .690” maximum ID. Internal raised weld seam must be present. (ID as Mfg. NO Grinding, Reaming, or Polishing Allowed) . Rear baffle holes .1285” maximum, inner baffle holes .0965” maximum. Silencer must be utilized as produced, with no modifications or alterations permitted. Strap or brace required to silencer for support, and to insure silencer does not turn and unscrew. 

Fuel Tank Requirements: Floor Mounted fuel tank mandatory (stock tank must be removed). Pulse type fuel pump allowed.

Fuel Pump Requirements: Fuel pump must be pulsed from either the crank case or the valve cover. You may install a flat metal plate in the original tank location for the purpose of mounting the throttle linkage and fuel pump.

Clutches: Stamped steel drum shoe type clutches only, No machined Billet drums allowed. No disc clutches allowed.

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).


Important Note:Any attempt to increase the RPM ’s of the BOX STOCK PROJECT,Stock Classes,engine(example:stronger/non stock valve springs or decreasing exhaust
restriction from stock levels)is strictly prohibited.Should this be allowed or preformed
will mandate the use of an aftermarket Billet style flywheel for high RPM use(Super
Box).ARC currently has these parts in their product line(part #’s 6618/6619)and they
are approved by AKRA for use,others may become available as demand increases.Note:
Under no circumstances is this type of flywheel allowed in the Box Stock Project (Stock
Classes),Stock Flywheel ONLY.

No other alterations to or from stock components are allowed

Any Questions about
AKRA Box Stock/6.5 Clone Rules for 2011
Call AKRA OFFICE at 704-764-8138