2000-2005 Yamaha F40B Outboard Service Manual, Page 108Get this manual
1POWER UNIT 4Install: Cylinder head cover Spark plugs Flywheel magnet assembly cover 5Connect: Blowby hose Fuel hoses Spark plug leads
MEASURING THE COMPRESSION PRESSURE
Before removing spark plug, use compressed air to blow away dirt accumulated in the spark plug well to prevent it from failing into the cylinder that is being tested
1Check: Valve clearance Out of specification -7 AdjustRefer to "ADJUSTING THE VALVE CLEARANCE" on page 3-142Warm-up: Engine 3Remove: Spark plug(-s) 4Install: Compression gauge CD (into the spark plug hole)