Shake, Rattle & Roll: Top Six Strange Motorcycle Noises
Are you a good listener? Are you one of those folks who hears things that go “bump” in the night and wonder “what the heck was that?” How about when you’re riding your motorcycle; do you ever hear strange sounds coming from that machine and wonder if it is trying to tell you something?
If odd new noises, sounds or vibrations are afoot, something probably is wrong, and in quite a number of cases, those sounds may be a warning. While a brand new motorcycle may sound the alarm with the same kind of odd sounds, these noises may be more likely to occur if you ride a vintage or high-mileage motorcycle.
In any given situation, with any machine, there are a number of possible sources of sounds both routine and unusual, but some may be distinctive enough to warn of specific types of problems. Your common rattle is generally some loose external component where a fastener has gone adrift and just needs to be tightened up or a new fastener put in.
But some of those problems may be urgent and rapid response may prevent or minimize potential damage. New clicks, rattles or ticking sounds may be indicators of things having more clearance than they should as a product of normal wear—often able to be adjusted.
1. Tick, tick tick:
For example, you are cruising along and you notice a strange, rhythmic ticking sound you’ve never heard before—not all the time, but it comes and goes at certain speeds. I had that happen a few years back and at first I suspected something in the valve train, so I stopped and listened to the engine and the noise went away, even when I revved the engine, except at a certain RPM.
The sound was difficult to locate at first, then I realized the strange sound was emanating from above the chassis. Very odd, but that highlights one of the problems with troubleshooting by sound – the actual source of the sound may be difficult to track down. In this case, it turned out to be the lens in the right hand rear view mirror had finally had enough and vibrated loose in the backing plate! At certain engine speeds, that created the right frequency of vibration and the mirror lens would vibrate against the backing plate. When the mirror was fixed, that particular odd noise went away.
My first guess being the valve train is usually a pretty fair place to start, however. Tappets in need of adjustment may send a service reminder by issuing progressively more noticeable ticking sounds and the volume of the sound may vary from barely audible to prominent. In some engines, clicking and ticking noises may occur when something as simple as low oil level is present, but may also indicate a valve sticking, loose cam chain or other valve train problems. A clicking or clattering sound while in motion may also indicate a primary drive chain in need of adjustment.
Locating the precise source of some engine noises can be tricky, but very helpful in sorting out what needs to be done. A mechanic’s stethoscope can be helpful in doing that. It works and looks much like a medical stethoscope, but with a metal probe replacing the diaphragm head. It can be very helpful in sorting a cam chain in need of adjustment from a tappet noise.
2. Bump & grind:
Perhaps one of the most ominous sounds that can emanate from a machine is a grinding sound—no matter how soft or vague. A grinding sound, whether accompanied by a vibration or not is one of those sounds that not only tends to result in immediate attention, it requires it.
An intermittent grinding noise, very often inconsistent in occurrence and sometimes accompanied by a new vibration in the handlebars under braking may be pretty easy to track down; front or rear brake pads in need of replacement.
This can also arise from a caliper sticking causing a brake pad to drag. This can be diagnosed by just pushing the bike by hand—if it doesn’t roll freely or if you stop after riding a short distance and don’t use the brake in question and find the rotor hot to the touch, a sticking caliper may be the problem. This may be an issue when taking a bike out of storage, so checking for brake caliper sticking by rolling the bike by hand and applying the brakes to check for it is a good idea.
In some instances, though, certain brake pads may emit that type of sound due to high humidity or moisture on the pads. Checking the brake lining thickness is in order and if humidity or moisture is a possible cause, simply using the brakes several times will usually clear the problem up.
Grinding sounds from engine or transmission may indicate a bearing failure somewhere and requires immediate shut-down and troubleshooting. Similarly wheel bearings that are anything less than smooth and quiet may be in need of attention. A wheel bearing failure while underway can cause wheel lock and a crash.
Another sound that may come up is a peculiar grinding or clunking sound I’ve heard in combination when the spline of the rear drive gear on a shaft-drive bike is in need of greasing. Remedied soon enough, it probably does not indicate any damage, but left unaddressed long enough, it may lead to excessive wear.
3. Creepy krink:
This is a sound I reserve pretty much for bikes with metallic chain final drive. It is an odd sound that may repeat regularly or irregularly. It is not to be ignored; I’ve heard it in three situations: first, on a bike that has not been ridden in a long time and the chain is badly corroded.
In this case, it may be present very noticeably when the bike is first being moved around or the rear wheel is rotated on the center stand. Lubrication of the chain may make the sound diminish or even disappear, but it may be a harbinger of early chain failure, even after it is silenced by lubrication.
The second instance this sound may occur in is when links literally get a kink in them, usually indicating a severe wear condition. Finally, this sound may be evidence of misaligned sprockets after chain tension adjustment.
Double-checking the alignment marks and chain tension at no less than three points of wheel rotation is in order. Properly adjusted final drive chain in good repair running on well-aligned sprockets also in good repair should be relatively quiet, with only the soft sound of the rollers engaging the sprockets as the rear wheel rotates.
4. Boo hiss:
One of the most common sounds heard around anything with tires is the nauseating hissing sound that emanates from a tire deflating at the worst possible time. But at least if you’re in the position to hear the tire going down, it means you’re probably stopped making the situation more an inconvenience than potential crash.
A flooded cell battery on a charger or charging system that is seriously overcharging the battery causing the electrolyte to off-gas can also cause a hissing sound as the gas is forced out of the overflow tube, out of a cell cap or out a crack in the case. Stopping the charging condition immediately is in order and protecting yourself from potential battery burst is essential.
Other sources for a hissing sound include a blown gasket somewhere, radiator leaks and exhaust system leaks. A blown head gasket, for example, may make a distinctive “chiff-chiff-chiff” type of sound, depending on engine type. Usually not immediately disabling, these sounds suggest service is needed soon.
5. Ring, ding, ping boom:
A barely perceptible pinging or dinging may be a sign of a potentially destructive condition known as detonation; often referred to as “spark knock.” Detonation is the pre-spark, premature ignition of part of the fuel charge in the cylinder caused by compression and high fuel mixture temperature.
Left uncorrected, temperatures and stresses in the combustion chamber can damage or destroy pistons, crank bearings, head components and cylinder walls. Evidence of the condition may be when the engine runs on for a few seconds even after the ignition is turned off.
Detonation once was primarily a problem of air-cooled high compression racing engines, but it can affect modern consumer-oriented engines, as well, particularly when a high-compression engine is run on low octane fuel. Contrary to popular belief, higher octane fuel does not have higher energy content or “power” than lower octane fuel; it does have higher temperature stability and therefore, more resistance to detonation.
Preignition can present with similar symptoms but differs from detonation in that it is an overheated engine component or the spark plug itself that may ignite the fuel charge prematurely instead of the fuel charge spontaneously combusting as in detonation.
6. Snap, crackle, pop:
A sharp snapping sound that may be irregular or regular may indicate a leakage or “short” of ignition energy to ground. This is particularly likely to be the case when it is accompanied by the engine “missing,” or hesitating.
The snapping sound can be caused by ignition energy arcing from a crack or flaw in the spark plug wire insulation or spark plug cap to the frame, engine or other metal component.
Careful inspection of the caps and wires is in order. Some may suggest running the engine in low light where arcing may be visible, but this is an inherently dangerous practice, since any fuel vapor present could ignite. Since these components are low-cost items, replacing them when in doubt makes sense.
The variety of sounds any given machine can create is pretty much unlimited. Familiarity with your own bike is a great asset in knowing which sounds it produces are normal and which are not. We hope this discussion of some of the more common ones is helpful in troubleshooting when you have to play it by ear.