Hesitation/Poor Acceleration

ATVs, snowmobiles, UTVs, personal watercraft and motorcycles, such as motocross and trail bikes are included in a category of personal vehicles known as power sport. These vehicles may be powered by two-stroke or four-stroke internal combustion engines, which may suffer from the same problems as the engine in your car, truck or SUV.

Many power sport vehicles are designed for off-road use, which may be seasonal in nature. Any engine not used on a regular basis and stored for an extended period of time can experience problems. Among those problems is poor acceleration or hesitation, which prevents your personal vehicle from accelerating smoothly.

Causes

A power sport engine, like other internal combustion engines, needs air, fuel and a spark to ignite the air/fuel mixture for it to run properly. If any of these elements are not supplied in the proper amounts and at the proper time, or if the spark is weak, your engine may not run smoothly or accelerate properly.  

Poor acceleration or hesitation may be a sign that your spark plug is worn or dirty, or the incorrect type of plug is being used. Examples of poor acceleration include an absence of response or a delayed reaction when you try to accelerate. Twisting the hand throttle does not immediately increase your speed and may cause your engine to stumble before increasing speed.  

What to Look For

Improper Spark Plug Type – Spark plugs come in a variety of types for different driving, or riding conditions and the plug in your engine may not suit your type of riding.

Dirty or Worn Spark Plug(s) – Carbon, oil residue and pitting on the spark plug electrodes will cause a weak or inconsistent spark, resulting in poor ignition and poor acceleration. 

Clogged Air Filter - A clogged air filter may not allow a sufficient amount of air into the combustion chamber, making the air/fuel mixture overly rich and causing poor acceleration.

Bad Gas - Bad gas will cause your engine to run erratically. Gas can go stale in as few as 30 days, especially gasoline mixed with ethanol as it is in many areas. Ethanol attracts moisture over time and the moisture will dilute the gas causing your engine to run poorly. 

Dirty Carburetor – Bad fuel may also cause harmful gum or varnish deposits to form inside your carburetor restricting or clogging vital carburetor passages and jets, resulting in uneven fuel supply and poor acceleration.

What to Do  

If the gas in your tank is old, it should be removed, properly disposed of, and replaced with fresh gas. As long as you’re checking the gas system, remove the gas cap and see if it has a vent—some caps will have an air vent to allow air to enter the tank as the gas is used. If it does, the vent should be cleaned or the gas cap replaced.

Your carburetor can be cleaned and adjusted by a visit to your favorite professional mechanic, who can also check your spark plugs and air filter. For any new parts that may be required, you should insist on products from a name-brand manufacturer, such as Champion. Also, make sure that whatever parts you buy are genuine, not low budget knock-offs..      

Results

Once your engine has been returned to tip-top condition, make sure you have a good grip on your vehicle the next time you want to accelerate, because this time your power sport vehicle won’t hesitate to get up and go. 

The content contained in this article is for informational purposes only and should not be used in lieu of seeking professional advice from a certified technician. We encourage you to consult with a certified technician if you have specific questions or concerns relating to any of the topics covered herein.