BRP Johnson 4HP - Powerhead

6-1
POWERHEAD
CONTENTS
POWERHEAD
CONTENTS
REMOVAL ................................................................................................................................................ 6-2
INSTALLATION ........................................................................................................................................ 6-5
DISASSEMBLY ........................................................................................................................................ 6-7
OIL FILTER / OIL PUMP ......................................................................................................................... 6-7
INTAKE MANIFOLD / THERMOSTAT ...................................................................................................... 6-7
CYLINDER HEAD / VALVE / ROCKER ARM ............................................................................................. 6-7
CYLINDER / PISTON / CRANKSHAFT / CONROD / CAMSHAFT ......................................................... 6-9
INSPECTION AND SERVICING ............................................................................................................. 6-11
CYLINDER HEAD ................................................................................................................................ 6-11
VALVE / VALVE GUIDE ......................................................................................................................... 6-12
VALVE SEAT SERVICING .................................................................................................................... 6-16
VALVE GUIDE REPLACEMENT ............................................................................................................ 6-17
VALVE SPRING ..................................................................................................................................... 6-18
CAMSHAFT ............................................................................................................................................ 6-19
CYLINDER / PISTON / PISTON RING ................................................................................................... 6-21
PISTON PIN / CONROD / CRANKSHAFT ............................................................................................. 6-26
OIL SEAL / BEARING ............................................................................................................................ 6-30
THERMOSTAT ....................................................................................................................................... 6-32
REASSEMBLY ....................................................................................................................................... 6-33
PISTON TO CONROD .......................................................................................................................... 6-33
PISTON RING TO PISTON .................................................................................................................... 6-34
CRANKSHAFT AND PISTON TO CYLINDER .......................................................................................... 6-35
CONROD CAP .................................................................................................................................... 6-35
CAMSHAFT TO CYLINDER .................................................................................................................. 6-36
CRANKCASE TO CYLINDER ................................................................................................................ 6-36
CYLINDER HEAD / VALVE ................................................................................................................... 6-37
CYLINDER HEAD TO CYLINDER .......................................................................................................... 6-38
PIVOT NUT / ROCKER ARM / VALVE CLEARANCE ................................................................................ 6-38
CYLINDER HEAD COVER .................................................................................................................... 6-39
INTAKE MANIFOLD / THERMOSTAT .................................................................................................... 6-39
OIL PUMP / OIL FILTER ....................................................................................................................... 6-39
OPERATION ........................................................................................................................................... 6-40
WATER COOLING SYSTEM ................................................................................................................. 6-40
ENGINE LUBRICATION SYSTEM .......................................................................................................... 6-41
NOTES .................................................................................................................................................... 6-42