The Yamaha Big Bear 400, a stalwart of the ATV world, is known for its reliability and utility. However, even the toughest machines have their weaknesses. Understanding the common issues that can plague the Big Bear 400 can save you time, money, and frustration in the long run, whether you're a seasoned rider or just starting out. This article delves into the problems often encountered with this popular ATV, offering insights and potential solutions to keep your Big Bear roaring.

So, Your Big Bear's Acting Up? Let's Troubleshoot!

Let's face it, no ATV is perfect. The Big Bear 400, while generally dependable, can experience a few common hiccups. Recognizing these problems early on is crucial for preventing more significant (and expensive) damage. We’ll break down the most frequent issues, explore their root causes, and offer practical steps to get your ATV back in top shape.

Common Problems at a Glance:

  • Starting Issues
  • Carburetor Problems
  • Electrical Gremlins
  • Suspension Woes
  • Brake Issues

Starting Problems: Why Won't It Fire Up?

One of the most frustrating issues is a Big Bear 400 that refuses to start. There are several potential culprits here, ranging from simple fixes to more complex repairs.

Possible Causes and Solutions:

  • Dead Battery: This is the most common reason for starting problems. Check the battery voltage with a multimeter. A healthy battery should read around 12.6 volts when fully charged. If it's low, try charging it. If it won't hold a charge, it's time for a new battery.
  • Faulty Starter Solenoid: The starter solenoid is a small relay that sends power to the starter motor. If it's bad, the starter won't engage. You can test the solenoid by listening for a click when you turn the key. If you don't hear a click, it might be faulty. You can also use a multimeter to check for continuity.
  • Bad Starter Motor: The starter motor itself could be the problem. If you hear a clicking sound but the engine doesn't turn over, the starter motor might be worn out or have a bad connection. Replacing the starter motor is usually the best solution.
  • Clogged Carburetor: A dirty carburetor can prevent the engine from getting the fuel it needs to start. We'll delve deeper into carburetor issues in the next section.
  • Spark Plug Problems: A fouled or worn spark plug can prevent the engine from firing. Remove the spark plug and inspect it. If it's black and oily, it's fouled. If the electrode is worn down, it needs to be replaced. Make sure you use the correct spark plug for your Big Bear 400.
  • Loose or Corroded Connections: Check all the wiring connections related to the starting system, including the battery terminals, starter solenoid connections, and ground connections. Clean any corrosion with a wire brush and tighten any loose connections.
  • Faulty Neutral Safety Switch: The neutral safety switch prevents the engine from starting unless the ATV is in neutral. If the switch is faulty, it might prevent the engine from starting even when it's in neutral. You can test the switch with a multimeter.

Carburetor Catastrophes: Fuel Delivery Frustrations

The carburetor is responsible for mixing fuel and air in the correct proportions for combustion. Carburetor issues are a common source of problems in the Big Bear 400, especially in older models.

Common Carburetor Issues:

  • Clogged Jets: The jets are small openings in the carburetor that control the flow of fuel. They can easily become clogged with dirt and debris, preventing the engine from getting enough fuel. This is the most common carburetor problem.
  • Dirty Carburetor Body: Over time, the carburetor body can accumulate dirt and varnish, which can affect its performance.
  • Float Problems: The float controls the fuel level in the carburetor bowl. If the float is sticking or damaged, it can cause the carburetor to flood or starve the engine of fuel.
  • Air Leaks: Air leaks in the carburetor can disrupt the fuel-air mixture, causing the engine to run poorly.

Solutions for Carburetor Problems:

  • Carburetor Cleaning: The best way to address carburetor problems is to clean it thoroughly. This involves disassembling the carburetor, cleaning all the parts with carburetor cleaner, and reassembling it. There are many excellent online tutorials that can guide you through this process.
  • Carburetor Rebuild Kit: If the carburetor is heavily worn or damaged, a rebuild kit might be necessary. A rebuild kit includes new jets, gaskets, and other parts that can restore the carburetor to like-new condition.
  • Adjusting the Air/Fuel Mixture: The air/fuel mixture screw controls the richness of the fuel mixture. Adjusting this screw can help to fine-tune the carburetor's performance. Consult your owner's manual for the correct setting.
  • Check for Air Leaks: Inspect the carburetor and intake manifold for any signs of air leaks. You can use a can of carburetor cleaner to spray around the joints. If the engine speed changes when you spray a particular area, it indicates an air leak.

Electrical Enigmas: Tracing Those Tricky Wires

Electrical problems can be particularly frustrating because they can be difficult to diagnose. The Big Bear 400 has a relatively simple electrical system, but there are still several potential points of failure.

Common Electrical Problems:

  • Blown Fuses: A blown fuse is often the first sign of an electrical problem. Check all the fuses in the fuse box and replace any that are blown.
  • Faulty Wiring: Damaged or corroded wiring can cause a variety of electrical problems. Inspect the wiring harness for any signs of damage.
  • Bad Ground Connections: Ground connections are essential for the electrical system to function properly. Make sure all the ground connections are clean and tight.
  • Faulty Switches: The switches for the lights, ignition, and other electrical components can fail over time.
  • Voltage Regulator Problems: The voltage regulator controls the voltage output of the charging system. If it's faulty, it can cause the battery to overcharge or undercharge.

Troubleshooting Electrical Issues:

  • Use a Multimeter: A multimeter is an essential tool for diagnosing electrical problems. It can be used to check voltage, current, and resistance.
  • Follow the Wiring Diagram: A wiring diagram can be invaluable for tracing electrical circuits and identifying potential problems.
  • Check for Continuity: Use a multimeter to check for continuity in the wiring harness. This can help you to identify broken wires or bad connections.
  • Test Components: Test the switches, voltage regulator, and other electrical components to see if they are functioning properly.

Suspension Sagging? Ride Rough? Suspension Solutions

A properly functioning suspension is crucial for a comfortable and safe ride. The Big Bear 400's suspension is relatively simple, but it can still experience problems over time.

Common Suspension Problems:

  • Worn Shocks: The shocks absorb bumps and provide a smooth ride. Over time, the shocks can wear out and lose their ability to dampen vibrations.
  • Worn Bushings: The bushings are rubber or plastic sleeves that connect the suspension components. They can wear out over time, causing excessive play in the suspension.
  • Broken Springs: The springs support the weight of the ATV and rider. They can break or sag over time, causing the suspension to bottom out easily.
  • Loose or Damaged Ball Joints: Ball joints connect the suspension to the wheels. They can become loose or damaged, causing steering problems and instability.

Addressing Suspension Issues:

  • Inspect the Shocks: Check the shocks for leaks, damage, or excessive wear. If they are leaking or worn out, they should be replaced.
  • Replace Worn Bushings: Replace any worn or damaged bushings to restore the suspension's tightness.
  • Replace Broken or Sagging Springs: Replace broken or sagging springs to restore the suspension's ride height and performance.
  • Check and Replace Ball Joints: Check the ball joints for looseness or damage. If they are loose or damaged, they should be replaced.
  • Adjust Preload: Many shocks have adjustable preload. Increasing the preload can stiffen the suspension and improve its handling. Consult your owner's manual for instructions on adjusting the preload.

Brake Blues: Stopping Power Problems

Reliable brakes are essential for safety. The Big Bear 400 typically uses drum brakes in the rear and disc brakes in the front (depending on the year). Both types of brakes can experience problems.

Common Brake Problems:

  • Worn Brake Pads (Disc Brakes): Brake pads wear down over time and need to be replaced.
  • Worn Brake Shoes (Drum Brakes): Brake shoes wear down over time and need to be replaced.
  • Leaking Brake Fluid: Brake fluid leaks can cause a loss of braking power.
  • Air in the Brake Lines: Air in the brake lines can make the brakes feel spongy and reduce their effectiveness.
  • Sticking Calipers (Disc Brakes): The brake calipers can stick, causing the brakes to drag.
  • Worn Brake Cables (Drum Brakes): The brake cables can stretch or break, reducing the braking force.

Troubleshooting Brake Issues:

  • Inspect Brake Pads/Shoes: Check the brake pads or shoes for wear. If they are worn down to the minimum thickness, they should be replaced.
  • Check for Leaks: Inspect the brake lines, calipers, and master cylinder for leaks. If you find a leak, repair it immediately.
  • Bleed the Brakes: Bleeding the brakes removes air from the brake lines. This can improve the brake feel and performance.
  • Clean and Lubricate Calipers: Clean and lubricate the brake calipers to prevent them from sticking.
  • Replace Brake Cables: Replace worn or broken brake cables to restore the braking force.

Frequently Asked Questions

  • Why is my Big Bear 400 backfiring? Backfiring is often caused by a lean fuel mixture or an exhaust leak. Check your carburetor settings and exhaust system for leaks.
  • My Big Bear 400 is running rough. What could be the problem? Rough running can be caused by a variety of issues, including a clogged carburetor, a faulty spark plug, or a vacuum leak.
  • How often should I change the oil in my Big Bear 400? It's generally recommended to change the oil every 100 hours of riding or once a year, whichever comes first.
  • My Big Bear 400's battery keeps dying. What could be causing this? A dying battery can be caused by a faulty charging system, a parasitic draw, or a bad battery. Have your charging system tested and check for any accessories that might be drawing power when the ATV is off.
  • Where can I find a service manual for my Big Bear 400? You can find service manuals online through various retailers or directly from Yamaha.

Keep Your Bear Roaring!

The Yamaha Big Bear 400 is a tough and reliable ATV, but like any machine, it can experience problems. By understanding the common issues and knowing how to troubleshoot them, you can keep your Big Bear running smoothly for years to come. Remember that regular maintenance is key to preventing many of these problems in the first place.