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Wall Stadium Clone Engine Rules sheet 2009 Season

ENGINE SPECIFIC TECH SHEET FOR: BOX STOCK CLONE 6.5 OVH
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. Any color engines are allowed but must meet box stock specs.

  Block may be cut to zero pop up

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. The only 2 headers allowed are the 5438C RLV or RAPP .880X18 HEADER gasket and or sealer allowed.
Bore and Stroke: Stock cylinder bore is 2.685” max. Stroke is 2.123” + / - .005”.

Carburetor requirements: Huayi or Rui-Ing model carbs 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 .042” MAX. Stock air cleaner assembly only on champ class.
Valve Train: Stock valve cover only with any stock configuration gasket, no sealer.

Carburetor/Fuel Tank Requirements: Floor Mounted fuel tank single feed fuel pumps only

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: Stock clone 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.  
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. Maximum running lift of .245” checked at valve as run.
Block Requirements: Block must remain stock as produced. Stub for governor may be removed and hole plugged.
No machining of block allowed except were noted. Welding to the block shall be for rod damage repair only and may not constitute a
functional modification.