OHV CLONE RULES

APPROVED ENGINES--OHV engines generally referred to as Clones with a maximum displacement of 200cc's.  (current legal engines include the Lifan, Grey Hound, Harbor Freight blue & yellow, Jaingdong, Yamakoyo, Blue Max)

ENGINE SPECIFIC TECH SHEET FOR BOX STOCK 6.5 OHV

Single cylinder, 2 valve, ohv 4 cycle

Important note:  All parts must be Box Stock factory production parts unless otherwise specified in these rules.  NO MACHINING OR ALTERATION OF PARTS IS ALLOWED UNLESS SPECIFICALLY NOTED.    All parts will be subject to comparison to a known box stock part( when performing 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 immediate disqualification of competitor along with forfeiture of 1/2 points earned to date in class and suspended for 2 races.  Second time offense: you will be moved out of the 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 seals are two angles,45 degrees valve face and 30 degrees top relief. Stock head bolts only, must have four.  Head gaskets maybe after market, must be of stock configuration.  No copper or aluminum gaskets allowed. One head gasket only! Any stock configuration gasket allowed on exhaust, no other sealer.

BORE & 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 up to .042 NO-GO.  Stock air cleaner assembly only.
FUEL REQUIREMENTS:  PUMP GAS ONLY, NO  NITRO

If you are running a floor mounted tank, Pulse type fuel pumps are allowed.  Fuel pump must be pulsed from either the crank case or the valve cover. You must install a flat metal plate in the original tank location for the purpose of mounting the throttle linkage and fuel pump.

VALVE TRAIN:  Stock valve cover only with any stock configuration gasket, no sealer.  Factory sealer rocker arms and push rods only.  Stock valves only 45 degree angle on both valves, no modifications allowed.  Only Box Stock valve springs . Max wire diameter on spring wire is .0705" with a maximum tension of 10.8lbs. at a height of .850".

IGNITION SYSTEM:  Stock Box Sysytem 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.    Pull rope may be removed to make it accessible for use with a starter box.

PISTON AND RINGS:  Must be unaltered Box Stock only.  NO MACHINING OF ANY TYPE ALLOWED.  

CONNECTING ROD:  Stock Box rod only.  NO MACHINING OF ANY TYPE ALLOWED.  Stock rod bolts only.

CRANKSHAFT REQUIREMENTS:  Stock Box crankshaft equired.  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.  See profile listed below.  The following Box Stock Cam Profile is NOW recognized by the Box Stock Project.

Box Stock Cam Profile Specs

CAMSHAFT REQUIREMENTS: DURATION CHECK FOR INTAKE AND EXHAUST LOBES.  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 GUAGE VARIANCES)

MAX INTAKE LIFT ON CAM .225" 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" TAKEN AT THE PUSHROD.
MAX EXHAUST LIFT AT THE VALVE>242" TAKEN ON VALVE SPRING RETAINER WITH ZERO LASH.


USE +/- 3 DEG ON ALL LIFT CHECKS

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.

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.)  Only the top three are alloawed to be claimed.  The protest fee is $50.00 and if you protest you must tear down also.  Any illegal parts  found will be confiscated and kept by the promoter.