6 Yamaha Big Bear 350 Common Problems (With Fixes)

The Big Bear 350 is Yamaha’s first-ever 4×4 ATV, launched in 1988. It debuted on the market to meet the growing demand for the 4WD ATVs with the latest, world-leading technology. The ATV is famous for its reliability among outdoor enthusiasts.

It’s a powerful and versatile ATV for adventure, hunting, and farming. However, Big Bear’s long history means you’re more likely to experience issues while riding it. Yamaha Big Bear 350 common problems include the ATV running rough, transmission failure, loss of power, and battery failure.

Do you own a problematic Big Bear 350? Keep reading and learn how to fix your ATV.

Running Rough

One of the most reported problems with the Big Bear 350 is the ATV running rough. The engine starts and idles properly but revs up and sputters after running for a few minutes.

Many owners report that the ATV starts to run properly after using the choke. But after turning off the choke, the ATV starts to run rough again.

Using the choke allows more fuel to go into your 4-wheeler’s carburetor. So, if the ATV runs properly after using the choke, it may have a fuel-related problem.

Start by inspecting the carburetor jets for clogs or improper adjustment of the fuel mixture screw. The goal is to richen the fuel mixture to allow more fuel into the carb. Spray some carb cleaner into every carburetor’s hole to clean any gunk blocking fuel flow.

Check and adjust the engine compression if your ATV keeps running rough. Over time, the valves get tight, reducing engine compression. Adjusting the valves may help fix this problem.

Losing Power

It’s common for an older engine to experience power loss issues after operating for several years. The Big Bear 350 features a 4-stroke, air-cooled engine with plenty of power. However, the engine becomes less powerful over time if not properly maintained.

Your ATV may feel less powerful when accelerating or climbing steep hills. Fortunately, you can resolve this issue by cleaning the carburetor. An old or worn carburetor can also cause power loss problems. Replace a worn or damaged carburetor if necessary.

Next, examine the air filter to ensure it allows sufficient airflow into the engine. Insufficient airflow causes the engine to run rich and lose power. Replace the filter if it looks blocked or worn.

Lastly, malfunctioning spark plugs can cause combustion problems and weaken the engine. Inspect the plugs and clean them if they have rust buildup. Alternatively, replace any defective plugs and secure them in place.

Transmission Failure

This ATV model is prone to various transmission issues, compromising your riding experience. Like many Yamaha Big Bear 350 common problems, transmission failure may occur due to improper maintenance.

For example, failure to check and add more transmission fluid can cause gear-shifting challenges. Moving parts may wear due to lubrication problems and cause occasional grinding noise. Topping off the reservoir with fresh fluid can help.

A blown transmission is another common issue your ATV may experience. Yamaha designed this 4×4 ATV to operate at 40 MPH. Exceeding this speed limit causes the transmission to overwork and eventually blow out. A blown transmission will cause difficulties in starting and running the ATV.

If you have a blown transmission, take your ATV to a certified Yamaha specialist for inspections. The specialist may repair or replace the entire transmission system.

Note: Avoid forcing your Big Bear 350 to exceed the recommended speed limit. Exceeding 40 MPH puts your ATV at risk of transmission damage.

Faulty Brake System

While the Yamaha Big Bear 350 is a rugged off-road vehicle, its brake system tends to fail over time. Excessive use, poor brake maintenance, and improper braking habits are the leading causes of brake failure in this ATV.

The rugged trail condition puts more pressure on the system while braking, causing parts to wear out or become loose.

If the brakes become unresponsive, the first component to check is the brake pads. The pads wear out quickly or become glazed due to excessive use or poor braking habits. Remove the worn or glazed brake pads and install new ones.

Do your brakes feel unresponsive or spongy even after installing new pads? If so, look for loose parts and tighten them.

Air trapped in the brake system may also cause the brakes to feel spongy. You can fix this by bleeding the brakes to remove any trapped air in the lines. Then, add brake fluid in the reservoir to the required level.

If the brake fluid level goes down faster than it should, there might be a leakage in the system. Examine the brake hose for leakages. A damaged hose will cause brake fluid to leak and need replacing.

Faulty Ignition System

If you’ve had your Yamaha Big Bear 350 for many years, you’re more likely to deal with a failing ignition system. A faulty ignition system can trigger several Yamaha Big Bear 350 common problems. For instance, your ATV may experience starting difficulties, loss of power, and intermittent backfiring.

The leading cause of a malfunctioning ignition system is loose connections or damaged wiring. Excessive vibrations during bumpy rides and dust are often to blame. Check the wiring from the ignition switch and tighten the loose connections.

If the wires appear frayed, use electrical tape to cover the frayed parts. You can replace the wires and connections if they appear damaged beyond repair. Then, replace the ignition switch if it looks worn or damaged.

Spark plugs could also be to blame if the ignition system malfunctions. Use a brake cleaner, sandpaper, or wire brush to clean dirt on the plugs. Replace any worn, broken, or corroded plug.

Ignition coil failure could also be to blame if your ATV’s ignition system malfunctions. A multimeter should help you test the coil for resistance. Replace the coil if necessary.

Battery Failure

Battery failure is a common problem with ATVs, and the Big Bear 350 is no exception. If the battery is defective, your ATV may experience starting difficulties and electrical component failure. The battery often fails due to corrosion on the terminals and loose terminal cables.

Bumpy rides, dust, and road salt are the leading causes of battery failure in this ATV. Locate the battery and remove its cover to examine the terminals. Corroded terminals inhibit proper current transmission, and the battery may not charge.

Clean the terminals and tighten the cable connections. You’ll need to replace the cables if they appear worn or damaged.

An aged battery tends to deteriorate gradually and eventually loses its ability to hold power. Test the battery with your multimeter. If the battery’s volts suggest it’s defective, replace the old battery.

How To Maintain Your Yamaha Big Bear 350

Routine maintenance can help prolong your ATV’s life. Use these tips to maintain your Big Bear 350 to ensure it runs smoothly for years.

  • Check the oil level regularly. 
  • Change the oil when necessary.
  • Wash the ATV to remove any dirt or debris accumulating on it.
  • Inspect the air filter and replace it when it is dirty.
  • Examine the tires before and after every ride. The goal is to maintain the recommended tire pressure and spot any irregularities on time.
  • Check the brake fluid levels and add more fluid when needed.
  • Inspect and replace the brake pads when necessary.
  • Check all electrical connections and wiring to ensure they’re in good condition.
  • Check the fuel filter regularly to spot issues earlier.
Yamaha Big Bear 350 common problems

Are Yamaha Big Bear 350 Problems a Deal Breaker?

Thankfully no. While the Big Bear 350 is prone to several issues, it’s a reliable and heavy-duty ATV for handling tough terrains. Despite its lower top speed, this ATV will be a great workhorse when hunting, sightseeing, or touring through the farm.

The Yamaha Big Bear 350 common problems may result from poor maintenance, improper handling, or regular wear and tear. Regularly maintaining and fixing issues will help keep your ATV in top condition for many years.