Motorcycle Not Running Smoothly? 10 Common Reasons (Solved)

Every beginner rider has had the dreaded, knock-knee moment when the first little thing feels off on your new (to you) bike. 

Presumably, when we pick up a bike from a dealership or private seller, it should be running as smoothly as possible, or it will be a tough sale. But entropy dictates that the bike will eventually start running a bit ragged and we need to be prepared for that.

Here’s a list of 10 common reasons your motorcycle isn’t running smoothly, and some of the easy ways to diagnose and fix the issues as they arise!

1. Incorrect Tire Pressure

If you’re like me, you like to keep track of your bike’s fuel consumption rate. On longer-distance rides, it’s important to know how far you can travel on a tank of gas.

If you’re experiencing a poor fuel economy, it may be due to low pressure in your tires. Check the sidewall of the tire for the PSI (pounds per square inch) rating of the tire. Now use a tire pressure gauge to check the actual inflation level of your tire. 

If you’re under the acceptable PSI, you’ll be getting bad gas mileage, a spongy feel to your suspension, and difficulty handling. Inflating to the correct PSI, somewhere in the middle of the range can clear all these problems up.

2. Old Brake Fluid

Brake fluid powers the hydraulic system needed for brake functioning. The pressure created by the fluid in the brake line is what compresses and releases the brake pads from your disc or drum brakes.

As time passes, brake fluid absorbs water, creating small deposits of rust which turn the yellow fluid a darker color.

Because brake fluid degrades, it is recommended to change it out for new fluid every 2 years. 

Sometimes a symptom of old brake fluid is a spongy feeling when you squeeze the hand brake or press down on the foot pedal for your rear brake. Other symptoms include loss of braking power or seized brake calipers.

If you’ve experienced any of these symptoms, you’ll want to bleed your brakes, which is loads less! HItting the brakes simply means slowly letting the old brake fluid out of the bleeder valve while you refresh it with new fluid.

3. Bad Or Dead Battery

Most motorcycles now include an electric motor starter that feeds off the battery. If you are having hard starts, or sudden power outages when riding, it could easily be a battery on its way out. 

Motorcycle batteries depend on power cells within the battery housing. When these have reached the end of their life they will no longer hold an electrical charge, and your starting and operating power are greatly diminished.

If your battery is fully dead or slowly draining, you’ll need to replace it. If you know the battery is new, and a slow drain is the issue, be sure to test some of the components of your electrical system to make sure a faulty regulator/rectifier isn’t the guilty party.

Related: Motorcycle Battery Won’t Fully Charge | Here’s Why (SOLVED)

4. Dirty Oil and Oil Filter

For me, there’s nothing like a fresh filter and load of oil for engine performance. If your engine is a little louder than it should be or your engine oil light is on, it’s time to swap out the old for new!

Oil lubricates your engine’s moving mechanism components. Heat, minute debris from metal in motion and carbon will slowly change your oil from a clear, viscous fluid to a dark substance that shouldn’t be in your engine much longer.

Professionals recommend changing your engine oil every 500 to 1,000 miles, and more frequently if you ride over long distances, in heavy traffic, or at higher RPMs. 

And if you don’t remember the last time you changed the bike’s oil and filter, go ahead and change it just to be sure. A quick check of the dipstick will show the color of your oil and whether it needs to be replaced. 

If you buy any used bike, especially from a private seller, be sure to check the quality of all your fluids before taking it out on the road.

5. Loose Or Over-Tightened Chain

A motorcycle’s chain can dictate how smoothly it glides over pavement, so don’t forget to check this component.

If your engine is revving high and loud or if your suspension feels taut and unforgiving, the chain is too tight!

An overly tight chain can cause some serious stress to the drive train’s sprockets and to the engine, which will have to run harder to make up for the tight chain’s friction.

Too loose of a chain will cause the chain to skip the sprocket teeth, give you a jolty power transmission, or fall off completely, leaving you without any get up and go!

Every manufacturer has a recommendation for the correct amount of play, or movement allowable on the chain. The tension rating is sometimes printed or stamped on your swingarm, but if you don’t see it, look up the tension rating in your owner’s manual.

With a little adjustment to tighten or loosen the chain, you’ll be riding a lot more smoothly than with a sloppy, loose, or rigidly tight chain.

6. Clogged Air Filter

The air filter on a motorcycle is the entry point for the air to reach the combustion chamber. It must remain clean so that the correct amount of air is taken in and mixed with the fuel.

If your air filter is clogged, you might notice the bike misfiring or bogging out and lacking acceleration power, especially at higher RPMs.

Little bits of dust and particulate from the surrounding air, especially on dusty or smogged-out roadways, will enter the fibers of the filter over time.

Check that filter for clogging and excess dust! An easy way, in a pinch, to clean out your air filter is to simply spray it with some compressed air.

The high-pressure blast of compressed air should blow off a lot of the dust and improve your overall power.

7. Wrong Air-to-Fuel Ratio

Another cause of the stuttering, bogging, and misfiring of an engine during acceleration is the air-to-fuel ratio.

Air and fuel are combined in the carburetor or fuel injectors to create the highly explosive fuel vapor that combusts to move the pistons in your engine. If the wrong amount of air, or too much or too little fuel, enters the combustion chamber, it will need adjusting to correct.

Fortunately for the lay mechanic, the answer is just a screw turn away!

Carburetors and fuel injector systems alike will have an air/fuel adjustment screw that just needs to be rotated either clockwise or counterclockwise to readjust the mixture.

Not sure if you’re running wet (too much fuel) or lean (too little fuel)? Take out the spark plugs and look at the insulator tips.

If a bike is running with too much fuel in the mixture, black carbon will be present. Alternately, if you have too much air in your mixture, the deposits on the insulator tip will be white.

Related: Motorcycle Stutter When Accelerating? Here’s Why (SOLVED)

8. Dirty Carburetor

Last but not least on the airflow culprit list is a dirty carburetor. If you have a fuel-injected bike, this section won’t pertain to you, but for anyone riding a pre-2000s bike, good chances are you have a carburetor.

If your carburetor is dirty, chances are your motorcycle isn’t going to be running the way you want it to.

The carburetor is the mechanism that mixes and transfers the fuel and air through a valve into the combustion chamber.

Because even the best air filter will let through tiny particles of dirt or debris, the carburetor can become fouled.

That, mixed with lower grade fuels, can create deposits all over the carburetor that can stick to the finely tuned valves that transfer air and fuel for combustion.

Common to find at any parts store is the carburetor cleaner. This gunk-removing godsend comes in an aerosol can and is very user-friendly (although it comes out fast and strong, so it’s a good idea to wear gloves, protective clothing, and eye protection when spraying this stuff).

Opening the air intake by removing the air filter, you can spray a ton of carburetor cleaner into the intake and it will dissolve a fair amount of deposits that have built up.

Alternately, you can add a cleaning solvent like Sea Foam to a full tank of fuel to clean out deposits in the carb.

Related: Motorcycle Idles But Won’t Accelerate (Solved & Explained)

9. Bad Spark Plugs

Sometimes when you feel a misfire or have a stutter or bogging sensation while accelerating, it’s time to check out the spark plugs.

Spark plugs sit at the top of the combustion chamber and add the spark needed to create the fuel explosion that causes your pistons to fire in an internal combustion engine.

The metal tip of the spark plug is an electrode where the spark is created and can become tarnished over time with carbon deposits from rich or lean fuel/air mixtures. Also, the ceramic insulator can break and crack.

Replacing spark plugs can be an easy task that leaves you with a sense of accomplishment, hurray!

Before you take the next steps, make sure that the area above and around the spark plugs is clean and clear of anything that might fall into the engine, as that could cause some serious problems!

With the motorcycle turned off, remove the rubber boot from the spark plug wire.

Using the correct sized socket or crescent wrench, loosen the spark plug. Carefully unscrew the spark plug and quickly screw the spark plug in place, making sure that nothing else gets into the engine. Tighten to manufacturer’s suggestions for the correct spark plug gap.

10. Dirt Invasion

Finally, make sure to keep that motorcycle clean! I mean, who wouldn’t want to keep their bike running smoothly and looking like a million bucks?

Not only will your bike sparkle and shine, turning heads by the dozens, but removing dirt and grime helps your bike run more smoothly.

A lot of important systems and components on your bike are exposed to the everyday accumulation of gunk, rust, dirt, and pollution from the air and the road.

Keeping foreign particulate from building up on the exterior of your bike is tantamount to the proper function of braking, shifting, drivetrain, and throttle systems.

Maybe you’ve noticed that accumulation is starting to cause problems in your brake calipers or clutch assembly, which are two common places where build-up is common.

How you maintain your bike is an indication of how your bike will run, and a clean, well-maintained bike is your best bet to keep your motorcycle running smoothly.