A compression test can help determine the source of cylinder leakage. Use CYLINDER COMPRESSION GAUGE (Part No. HD-33223-1) with a screw-in type adapter.
NOTE
All Twin Cam engines use a 12 mm adapter with the compression gauge.
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. Remove air cleaner. See 4.5 AIR CLEANER ASSEMBLY.
4. Disconnect TCA connector [211] from the induction module.
NOTE
Never use a metal object to hold the throttle plate open.
Damage to the throttle plate or throat of the induction module may result.
5. Insert a 0.75 in (19 mm) diameter by approximately 12 in (305 mm) long wooden or nylon dowel to hold the throttle valve open.
6. Connect compression tester to front cylinder per manufacturer’s instructions.
7. Make sure transmission is in neutral. Crank engine continuously through five to seven full compression strokes and note gauge readings at the end of the first and last compression strokes. Record test results.
8. Disconnect both ACRs and repeat test.
9. Connect ACRs.
10. Repeat tests on rear cylinder.
11. Hold throttle valve open and remove dowel. Connect TCA connector [211] when tests are complete.
12. Clear codes when test is complete.
13. Install the air cleaner. See 4.5 AIR CLEANER ASSEMBLY.
14. Refer to Table 3-28. If the final readings are within specifications and do not indicate more than a 10 percent variance between cylinders, compression is considered normal. If compression does not meet specifications, refer to
Table 3-29 for possible causes.
15. If readings do not meet specifications, inject approximately 1/2 oz (15 ml) engine oil into each cylinder and repeat the compression tests on both cylinders. Readings that are considerably higher during the second test indicate worn piston rings.
16. Install the spark plugs and tighten to 12-18 ft-lbs (16.3-24.4 Nm). Connect spark plug wires.
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