Engine Noises: What Is Normal and What Is Not

Some Harley noises are just how the engine sounds. Knowing which is which saves a fortune.

These engines are air-cooled, have a lot of reciprocating mass, and are mechanically noisy by design. Riders coming from quieter machines hear normal operation and panic; long-time owners sometimes ignore a genuine warning because "they all do that". Both are expensive. The useful skill is telling them apart.

Tools

• A mechanic's stethoscope, or a long screwdriver used as one
• A quiet space
• A phone to record the noise
• Service manual

Listen properly before you diagnose

Record it on your phone. A noise you can play back is a noise you can share with a mechanic, compare over time, and listen to without the engine running.

Establish what the noise TRACKS. Does it change with engine speed, or with road speed? Engine speed means the engine or primary. Road speed only means wheels, belt or brakes. That one question eliminates half the possibilities.

Does it change with LOAD, or only with revs? Does it appear cold and disappear warm, or the reverse? A noise that goes away as the engine warms is usually clearances closing up as metal expands — often benign. One that APPEARS when hot is more serious.

Locate it with a stethoscope or a long screwdriver handle to your ear, touching the cases in turn. Keep away from anything that moves.

Usually normal

A brief top-end tick on a cold start that quietens within a minute or so — hydraulic lifters filling and clearances closing. Normal on these engines.

A general mechanical clatter from the top end, audible at idle. Air-cooled engines have no water jacket to muffle them; this is what they sound like.

A single clunk into first gear from neutral. These gearboxes do that.

Some primary noise — a whirr or light rattle — particularly on Twin Cam engines at idle. Worth knowing what YOUR bike sounds like normally so you can hear a change.

Get it looked at

A DEEP, HEAVY KNOCK that gets worse with load, low down in the engine. Stop riding. Bottom-end noises do not get better and continuing turns a repair into a replacement.

A TICK THAT GETS LOUDER AS IT WARMS, rather than quieter — the opposite of the normal cold tick. Suspect valve train or an exhaust leak at the port.

A RHYTHMIC TICK THAT TRACKS ENGINE SPEED and is loudest at a joint, worse cold: that is an exhaust leak, not an engine fault. See the exhaust guide.

A CLATTER OR RATTLE FROM THE PRIMARY on startup and at low revs on a Twin Cam, often described as a marble in a can, commonly points at the compensator. It is a known wear item and it will not improve on its own.

ANY new noise accompanied by a change in oil pressure, oil consumption, or metal on the drain plug is not a noise problem. It is a mechanical problem that is also making a noise.

A SQUEAL OR SCRAPE THAT TRACKS ROAD SPEED is brakes or a wheel bearing, not the engine.

What to tell a mechanic

Bring the recording, and be able to answer: cold or hot, engine speed or road speed, under load or free-revving, when it started, and what changed just before it started.

"It makes a noise" costs diagnostic hours. Those five answers cut it down enormously and they cost you nothing to collect.

Parts for this job

Check fitment for your own model and year before ordering — add your bike and we will flag what fits.

Other Harley how-to guides

This guide covers procedure and judgement. Torque figures, fluid capacities, gaps and tension settings are specific to your model and year and must come from the factory service manual for your motorcycle — we deliberately do not print numbers we cannot stand behind for your bike. Independent aftermarket retailer, not affiliated with Harley-Davidson, Inc.