The Yamaha Big Bear 350: a workhorse ATV known for its reliability and ruggedness. But even the most dependable machines can face their share of challenges. This article aims to equip you with the knowledge to tackle common issues that might arise with your Big Bear 350, keeping you on the trails and out of the shop.

What Makes the Big Bear 350 So Popular (and Why Understanding Problems Matters)

The Big Bear 350 carved a niche for itself as a practical, no-frills ATV. It's simple to operate, relatively easy to maintain, and boasts enough power for most utility tasks and recreational riding. This enduring popularity means there are still a lot of these machines out there, many with significant hours on them. Understanding the common problems that crop up, especially on older models, allows you to proactively maintain your ATV, diagnose issues quickly, and potentially save yourself a lot of money in repair bills. Knowing the ins and outs of your Big Bear 350 ensures you can keep it running strong for years to come.

The Usual Suspects: Common Problems You Might Encounter

Let's dive into some of the most frequently reported issues with the Yamaha Big Bear 350. We'll cover the symptoms, potential causes, and some troubleshooting steps you can take.

**Starting Problems: When Your Bear Refuses to Wake Up**

A Big Bear that won't start is a frustrating experience. Here's a breakdown of potential culprits:

  • Dead or Weak Battery: This is often the first place to look. Batteries degrade over time, especially if not properly maintained.
    • Symptoms: Slow cranking, clicking sounds when trying to start, or no response at all.
    • Troubleshooting: Check the battery voltage with a multimeter. It should read around 12.6 volts when fully charged. Try charging the battery with a battery tender. If it still struggles, it's likely time for a replacement.
  • Faulty Starter Motor: The starter motor is responsible for turning the engine over.
    • Symptoms: Grinding noises during starting, the starter motor spinning but not engaging the engine, or complete silence.
    • Troubleshooting: Check the starter motor connections for corrosion or loose wires. You can also try tapping the starter motor with a hammer while attempting to start the ATV (this sometimes works temporarily to free up a stuck armature). Ultimately, a failing starter motor often requires replacement.
  • Dirty Carburetor: The carburetor mixes air and fuel for combustion. A dirty carb can cause starting and running issues.
    • Symptoms: Difficulty starting, especially when cold, rough idling, stalling, and poor throttle response.
    • Troubleshooting: Cleaning the carburetor is a common maintenance task. You can use carburetor cleaner spray to remove deposits. If the carb is severely clogged, a complete disassembly and cleaning might be necessary.
  • Clogged Fuel Filter: A clogged fuel filter restricts fuel flow to the carburetor.
    • Symptoms: Similar to a dirty carburetor – difficulty starting, poor performance, and stalling.
    • Troubleshooting: Replace the fuel filter. This is an inexpensive and easy preventative maintenance task.
  • Spark Plug Issues: A fouled or worn spark plug can prevent the engine from firing.
    • Symptoms: Difficulty starting, misfires, and poor fuel economy.
    • Troubleshooting: Remove the spark plug and inspect it. Look for signs of fouling (carbon buildup), damage, or excessive wear. Clean or replace the spark plug as needed. Make sure to use the correct spark plug specified for your Big Bear 350.
  • Ignition System Problems: Issues with the CDI (Capacitor Discharge Ignition) unit, ignition coil, or stator can also prevent the engine from starting.
    • Symptoms: No spark at the spark plug, intermittent starting problems, or complete engine failure.
    • Troubleshooting: This requires more advanced diagnostic skills and tools, such as a multimeter and a spark tester. It might be best to consult a qualified mechanic for these issues.

**Running Rough: Performance Problems on the Trail**

Once you get your Big Bear started, you want it to run smoothly. Here are some common running issues:

  • Dirty Carburetor (Again!): As mentioned before, a dirty carb is a frequent culprit for running problems.
  • Valve Adjustment: Over time, the valve clearances can change, affecting engine performance.
    • Symptoms: Ticking noises from the engine, loss of power, and difficulty starting.
    • Troubleshooting: Valve adjustment is a more involved process that requires specific tools and knowledge. Consult your service manual or a qualified mechanic.
  • Worn Piston Rings: Worn piston rings can cause a loss of compression, leading to poor performance and excessive oil consumption.
    • Symptoms: Blue smoke coming from the exhaust, loss of power, and high oil consumption.
    • Troubleshooting: A compression test can help determine if the piston rings are worn. This is a more significant repair that often involves rebuilding the engine.
  • Exhaust Leaks: Leaks in the exhaust system can affect engine performance.
    • Symptoms: Loud exhaust noise, reduced power, and poor fuel economy.
    • Troubleshooting: Inspect the exhaust system for cracks, holes, or loose connections. Repair or replace any damaged components.
  • Air Filter Problems: A dirty or clogged air filter restricts airflow to the engine.
    • Symptoms: Reduced power, poor fuel economy, and black smoke from the exhaust.
    • Troubleshooting: Clean or replace the air filter regularly.
  • Fuel Delivery Issues: Problems with the fuel pump (if equipped), fuel lines, or fuel tank vent can also cause running problems.
    • Symptoms: Stalling, hesitation, and lack of power, especially under load.
    • Troubleshooting: Check the fuel lines for kinks or blockages. Make sure the fuel tank vent is clear. If your Big Bear has a fuel pump, test its output pressure.

**Transmission Troubles: Shifting and Drivetrain Issues**

The Big Bear 350's transmission is generally reliable, but issues can arise:

  • Difficulty Shifting: This can be caused by several factors, including a worn shift linkage, a bent shift fork, or low oil level.
    • Symptoms: Difficulty shifting gears, grinding noises during shifting, or the transmission popping out of gear.
    • Troubleshooting: Check the shift linkage for looseness or damage. Make sure the transmission oil level is correct. If the problem persists, internal transmission damage may be the cause, requiring professional repair.
  • Clutch Problems: The clutch can wear out over time, leading to slipping or grabbing.
    • Symptoms: Slipping clutch (engine revs up but the ATV doesn't accelerate), grabbing clutch (jerky engagement), or difficulty shifting.
    • Troubleshooting: Check the clutch cable adjustment. If the clutch is worn, it will need to be replaced.
  • Differential Problems: The front or rear differential can experience issues, such as worn bearings or damaged gears.
    • Symptoms: Unusual noises from the differential, vibration, or difficulty turning.
    • Troubleshooting: Check the differential oil level. If the problem persists, the differential may need to be disassembled and inspected.
  • CV Joint Issues: The CV joints on the axles can wear out, especially if the protective boots are damaged.
    • Symptoms: Clicking or popping noises when turning, especially at full lock.
    • Troubleshooting: Inspect the CV joint boots for cracks or tears. If the boots are damaged, replace them as soon as possible to prevent further damage to the CV joint.

**Brake Problems: Stopping Power is Essential**

Brakes are crucial for safety. Here are some common brake issues:

  • Worn Brake Pads or Shoes: Brake pads and shoes wear out over time and need to be replaced.
    • Symptoms: Squealing noises when braking, reduced braking power, or a spongy brake pedal.
    • Troubleshooting: Inspect the brake pads and shoes for wear. Replace them if they are worn to the minimum thickness.
  • Leaking Brake Fluid: Leaks in the brake lines or master cylinder can cause a loss of braking power.
    • Symptoms: Spongy brake pedal, reduced braking power, and visible brake fluid leaks.
    • Troubleshooting: Inspect the brake lines, master cylinder, and calipers for leaks. Repair or replace any damaged components. Bleed the brakes after repairing any leaks.
  • Sticking Calipers: The brake calipers can stick, causing the brakes to drag.
    • Symptoms: Overheating brakes, reduced fuel economy, and pulling to one side when braking.
    • Troubleshooting: Clean and lubricate the brake caliper slides. If the caliper is severely corroded, it may need to be rebuilt or replaced.

Proactive Maintenance: Preventing Problems Before They Start

The best way to deal with Big Bear 350 problems is to prevent them in the first place. Regular maintenance is key. Here's a checklist:

  • Regular Oil Changes: Change the engine oil and filter according to the manufacturer's recommendations.
  • Air Filter Maintenance: Clean or replace the air filter regularly.
  • Spark Plug Inspection: Inspect and replace the spark plug as needed.
  • Carburetor Cleaning: Clean the carburetor periodically to prevent clogging.
  • Fuel Filter Replacement: Replace the fuel filter regularly.
  • Brake Inspection: Inspect the brakes regularly and replace worn pads or shoes.
  • Tire Pressure: Maintain proper tire pressure.
  • Lubrication: Lubricate all moving parts, such as the suspension components and shift linkage.
  • Battery Maintenance: Keep the battery charged and clean the terminals.
  • Storage: Properly store your Big Bear 350 when not in use. Use a fuel stabilizer and disconnect the battery.

Frequently Asked Questions

  • Why is my Big Bear 350 backfiring? Backfiring can be caused by a lean fuel mixture, exhaust leaks, or ignition timing issues. Check the carburetor, exhaust system, and ignition system.
  • How often should I change the oil in my Big Bear 350? Refer to your owner's manual, but typically every 100 hours of use or once a year is recommended.
  • What type of oil should I use in my Big Bear 350? Use a high-quality ATV oil that meets the manufacturer's specifications.
  • My Big Bear 350 is overheating. What could be the problem? Overheating can be caused by a low coolant level, a clogged radiator, or a faulty water pump. Check these components and ensure proper cooling system function.
  • Where can I find parts for my Big Bear 350? Many online retailers and local ATV shops carry parts for the Big Bear 350.

Keeping Your Bear Roaring

The Yamaha Big Bear 350 is a tough and reliable ATV, but like any machine, it requires proper maintenance and care. By understanding the common problems and following a regular maintenance schedule, you can keep your Big Bear running strong for years to come and enjoy countless hours of trouble-free riding. So, get out there, hit the trails, and enjoy the ride!