NOTE
On vehicles with automatic compression release (ACR), verify the ACRs are closed for this test. Perform the test with the ignition/light switch in the OFF position.
The cylinder leakdown test will help pinpoint leaking valves, worn, damaged or stuck piston rings and blown head gaskets.
The cylinder leakage tester applies compressed air to the cylinder at a controlled pressure and volume. It then measures the percent of leakage from the cylinder.
Use the CYLINDER LEAKDOWN TESTER (Part No. HD-35667-A). Follow the specific instructions supplied with the tester.
The following are some general instructions that apply to Harley-Davidson V-twin engines:
1. Run motorcycle until engine is at normal operating temperature. Stop engine.
2. Disconnect spark plug wires. Clean around plug base and remove plugs.
3. Rotate crankshaft until piston in the cylinder being tested is at top dead center (TDC) of compression stroke (both
valves closed) during the test.
4. Engage transmission in highest gear and lock the rear brake. This prevents the engine from turning over when
air pressure is applied to the cylinder.
NOTE
Before performing the cylinder leakdown test, verify the tester it self is free from leakage. Apply a soap solution around all tester fittings. Connect cylinder leakdown tester to compressed air source. Look for any bubbles that indicate leakage from the tester.
5. Following the manufacturer’s instructions, perform a cylinder leakdown test on the front cylinder. Make a note of the percent of leakage. Leakage greater than 10 percent indicates internal engine problems.
6. Listen for air leaks at throttle body, exhaust pipe and head gasket. Air escaping through the throttle body indicates a leaking intake valve. Air escaping through the exhaust pipe indicates a leaking exhaust valve.
NOTE
If air is escaping through valves, verify that piston is still at TDC or check for correct pushrod length.
7. Repeat procedure on rear cylinder.
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