Imperfect seal at gaskets, push rod cover, washers, etc.
If compression is below 100 psi (6.89 Bar) for 1100 cc engines or 150 psi (10.3 Bar) for 1200 cc engines.
Valve guide(s) or seal(s) worn or damaged.Note: Before performing the cylinder leakage test, verify that the tester itself is free from leakage to obtain the most accurate test results.The following check list of possible operating troubles and their probable causes will be helpful in keeping a motorcycle in good operating condition.The piston in the cylinder being tested must be at top dead center of compression stroke (both valves closed) during the test.Starter control circuit, relay, or solenoid faulty.Incorrect clutch release adjustment.Publisher: Clymer Manuals - 2006 Author: Ron Wright Binding: Paperback - 7 x 10 inches Pages: 446 - Hundreds of b w photos and illustrations isbn.Damaged wire or loose wire connection at ignition coil, battery or ECM connector.Cylinder head casting's porosity usace project manager manual allowing oil to drain into combustion chamber.BMW F650CS Repair, manual.

Aprilia RSV Mille 2002, service, manual.
Clogged feed line (ice and sludge, freezing temperatures).
Compression low on first stroke, does not build up much on following strokes.Remove the air cleaner and set the throttle in the wide open position.Spark Plug Fouls Repeatedly.Note: For cold weather os x crack wep starts, always disengage clutch.Partially plugged fuel injectors.