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Model: BP-1

MANUFACTURED BY:
McCULLOCH MOTORS CORP.
LOS ANGELES, CALIFORNIA, U.S.A.
SERIES OR ASSEMBLY NUMBER:
none
YEAR INTRODUCED:
1962
YEAR DISCONTINUED:
1963
ENGINE DISPLACEMENT:
2.7 cu. in. (44cc)
NUMBER OF CYLINDERS:
1
CYLINDER BORE:
1.75 in. (44.4mm)
PISTON STROKE:
1.125 in. (28.5mm)
PISTON RING THICKNESS:
CYLINDER TYPE:
Aluminum with cast iron sleeve
INTAKE METHOD:
Balance piston acts as intake valve
MANUFACTURER ADVERTISED H.P.:
4.2 @ 10,000 RPM
WEIGHT:
15 Lbs. (powerhead only)
OPERATOR CONFIGURATION:
One Man operation
HANDLEBAR SYSTEM:
Rigid
CHAIN BRAKE:
none
CLUTCH:
Centrifugal
DRIVE TYPE:
Bevel Gear reduction 2.0:1 or 2.9:1 ratios
CONSTRUCTION:
Die cast magnesium
MAGNETO TYPE:
McCulloch
CARBURETOR:
McCulloch
MAJOR REPAIR KIT:
n/a
MINOR REPAIR KIT:
n/a
AIR FILTER SYSTEM:
Flocked wire screen
STARTER TYPE:
McCulloch automatic rewind
OIL PUMP:
Automatic
MAXIMUM ENGINE RPM:
Goverened at 12,000
IDLE RPM:
IGNITION TIMING:
fixed at 27 degrees before TDC
BREAKER POINT SETTING:
0.018 in. (0.45mm)
FLYWHEEL/COIL AIR GAP:
0.008 to 0.010 in. (0.2 to 0.25 mm)
SPARK PLUG TYPE:
AC C45W
SPARK PLUG GAP:
0.025 in. (0.63mm)
CRANKSHAFT MAIN BEARINGS:
Ball
FUEL TANK CAPACITY:
FUEL OIL RATIO:
20:1
RECOMMENDED FUEL OCTANE:
Regular
MIX OIL SPECIFICATION:
McCulloch two-stroke chain saw mix oil
CHAIN PITCH:
9/16 in.
CHAIN TYPE:
McCulloch Auto-Mac with built in sharpener
BAR MOUNT PATTERN:
SHORTEST GUIDE BAR SUPPLIED:
16 in. (40cm)
LONGEST GUIDE BAR SUPPLIED:
24 in. (61cm)
COLOUR SCHEME:
McCulloch Yellow with Black
PAINT CODES:
ILLUSTRATED PARTS LIST:
SERVICE MANUAL:

COMMENTS:
Worlds only Balanced Piston engine chain saw. The BP-1 is a high speed engine utilizing one piston for power and one for balance and as a sliding intake valve. This saw was sold for a very short period of time and then withdrawn from the market by McCulloch. Because of the RPM that the engine was capable of if the governor failed it was feared that it would disintegrate and injure the operator.


Photographs of BP-1 taken by M. Acres in Nelson, B.C. Canada, September 1962

 

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