Abnormal engine noise (Honda XRV750 Africa Twin)

Knocking or pinking

• Carbon build-up in combustion chamber. Use of a fuel additive that will dissolve the adhesive bonding the carbon particles to the piston crown and chamber is the easiest way to remove the buildup. Otherwise, the cylinder heads will have to be removed and decarbonised (Chapter 2).
• Incorrect or poor quality fuel. Old or improper fuel can cause detonation. This causes the knocking or pinking sound. Drain the old fuel and always use the recommended grade fuel (Chapter 4).
• Spark plug heat range incorrect. Uncontrolled detonation indicates that the plug heat range is too hot. The plug in effect becomes a glow plug, raising cylinder temperatures. Install the proper heat range plug (Chapter 1).
• Improper air/fuel mixture. This will cause the cylinders to run hot and lead to detonation. Clogged jets or an air leak can cause this imbalance. See Chapter 4.

Piston slap or rattling

• Cylinder to-plston clearance excessive. Caused by improper assembly. Inspect and overhaul top-end parts (Chapter 2).
• Connecting rod bent. Caused by over-revving, trying to start a badly flooded engine or from ingesting a foreign object into the combustion chamber. Replace the damaged parts (Chapter 2). Piston pin or piston pin bore worn or seized from wear or lack of lubrication. Replace damaged parts (Chapter 2).
• Piston ring(s) worn, broken or sticking. Overhaul the top-end (Chapter 2).
• Piston seizure damage. Usually from lack of lubrication or overheating. Replace the pistons and cylinder block with new ones, as necessary (Chapter 2).
• Connecting rod upper or lower end clearance excessive. Caused by excessive wear or lack of lubrication. Replace worn parts with new ones.

Valve noise

• Incorrect valve clearances. Adjust the clearances by referring to Chapter 1.
• Valve spring broken or weak. Check and replace weak valve springs (Chapter 2).
• Camshaft(s) or cylinder head(s) worn or damaged. Lack of lubrication at high rpm is usually the cause of damage. Insufficient oil or failure to change the oil at the recommended intervals are the chief causes. Since there are no replaceable bearings in the head, the head itself and/or the camshaft will have to be replaced if there is excessive wear or damage (Chapter 2).

Other noise

• Cylinder head gasket(s) leaking.
• Exhaust pipe leaking at cylinder head connection. Caused by improper fit of pipe or loose exhaust flange. All exhaust fasteners should be tightened evenly and carefully. Failure to do this will lead to a leak.
• Crankshaft runout excessive. Caused by a bent crankshaft (from over-revving) or damage from an upper cylinder component failure. Can also be attributed to dropping the machine on either of the crankshaft ends.
• Engine mounting bolts loose. Tighten all engine mount bolts (Chapter 2).
• Crankshaft bearings worn (Chapter 2).
• Camchains, guide blades or tensioner blades worn. Replace according to the procedure in Chapter 2.
• Camchain tensioner failure (Chapter 2).