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OCR CLONE ENGINE TECHEngines are 6.5 HP OHV single cylinder engines. All parts must be factory stock as supplied from factory unless stated otherwise in this tech manual. All parts may be subject to comparison to known stock parts.
(1) 27.5cc chamber volume minimum, checked at TDC.
(2) Carburetor- Huayi or RUI_ING carb. only.
You must use a gasket between carb. and intake. No other sealer allowed.
Choke must be intact as from factory but may be fixed in open position.
Choke Bore: .810 no-go
Venturi – .615 no-go
Rear carb. Bore: .751 no-go
Main jet: .042 Max. no-go
Emulsion tube must remain stock.
Aftermarket air filter and adapter allowed. Adapter 1.375 max. length.
(3) Valve Train:
Stock valve cover only. Valve cover may be drilled and fitted with a fitting to pulse the fuel pump. No other modification.
Stock valves with 45% angles only. Must not be altered in any way such as polishing, lightning etc.
Stock rocker arms and pushrods with no modifications.
Max. Wire diameter of valve springs is .070.
Max. Spring tension at .850 = 10.8 lbs. Maximum.
(4) Ignition system must be stock as from factory.
Kill switch and oil sensor may be disabled and removed.
Flywheel cannot be altered in any way. Stock flywheel with plastic fins only as from factory.
Stock unaltered flywheel key only.
(5) Piston, rings, connecting rod and crankshaft must be stock as from factory.
No grinding, polishing, lightning or addition of any materials allowed.
Stock rod bolts must be used.
Crankshaft journal diameter is 1.180”max.-1.175” min..
(6) Stock camshaft as from factory only. No modifications of any kind allowed.
Maximum valve lift .242 taken off of spring retainer with 0 lash. (Exhaust).
Maximum valve lift .238 taken off of spring retainer with 0 lash. ( Intake).
(7) Block must be stock except you may remove the governor and plug the holes.
No machining allowed on block.
(8) It is recommended that a remote fuel tank be used. You may remove the fuel tank and mount a plate where tank was mounted to mount a remote fuel pump. Fuel pump must be pulsed from the valve cover or crankcase only.
(9) Header and Muffler:
You may replace the stock muffler with any one piece, single stage header with BS style muffler # 89966 or aftermarket muffler of same size and design.
Header with muffler installed must measure between 10” min. and 14” max. measured on outside. Header can be no bigger than .750 O.D. and must be steel.
Muffler may be welded to header or screwed into header.
clone tech
OCR CLONE ENGINE TECHEngines are 6.5 HP OHV single cylinder engines. All parts must be factory stock as supplied from factory unless stated otherwise in this tech manual. All parts may be subject to comparison to known stock parts.
(1) 27.5cc chamber volume minimum, checked at TDC.
(2) Carburetor- Huayi or RUI_ING carb. only.
You must use a gasket between carb. and intake. No other sealer allowed.
Choke must be intact as from factory but may be fixed in open position.
Choke Bore: .810 no-go
Venturi – .615 no-go
Rear carb. Bore: .751 no-go
Main jet: .042 Max. no-go
Emulsion tube must remain stock.
Aftermarket air filter and adapter allowed. Adapter 1.375 max. length.
(3) Valve Train:
Stock valve cover only. Valve cover may be drilled and fitted with a fitting to pulse the fuel pump. No other modification.
Stock valves with 45% angles only. Must not be altered in any way such as polishing, lightning etc.
Stock rocker arms and pushrods with no modifications.
Max. Wire diameter of valve springs is .070.
Max. Spring tension at .850 = 10.8 lbs. Maximum.
(4) Ignition system must be stock as from factory.
Kill switch and oil sensor may be disabled and removed.
Flywheel cannot be altered in any way. Stock flywheel with plastic fins only as from factory.
Stock unaltered flywheel key only.
(5) Piston, rings, connecting rod and crankshaft must be stock as from factory.
No grinding, polishing, lightning or addition of any materials allowed.
Stock rod bolts must be used.
Crankshaft journal diameter is 1.180”max.-1.175” min..
(6) Stock camshaft as from factory only. No modifications of any kind allowed.
Maximum valve lift .242 taken off of spring retainer with 0 lash. (Exhaust).
Maximum valve lift .238 taken off of spring retainer with 0 lash. ( Intake).
(7) Block must be stock except you may remove the governor and plug the holes.
No machining allowed on block.
(8) It is recommended that a remote fuel tank be used. You may remove the fuel tank and mount a plate where tank was mounted to mount a remote fuel pump. Fuel pump must be pulsed from the valve cover or crankcase only.
(9) Header and Muffler:
You may replace the stock muffler with any one piece, single stage header with BS style muffler # 89966 or aftermarket muffler of same size and design.
Header with muffler installed must measure between 10” min. and 14” max. measured on outside. Header can be no bigger than .750 O.D. and must be steel.
Muffler may be welded to header or screwed into header.
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