Yamaha Big Bear Problems

The Yamaha Big Bear, a stalwart of the ATV world for decades, has earned a reputation for its ruggedness and reliability. However, even the toughest machines aren't immune to issues. Understanding common problems associated with your Big Bear can save you time, money, and frustration, allowing you to keep your trusty ATV running smoothly for years to come. Let's dive into some of the most frequently encountered issues and, more importantly, how to tackle them.

My Big Bear's Hard to Start! What's Going On?

A hard-starting Big Bear is a classic complaint, and there are several potential culprits. Let's break down the usual suspects:

The Carburetor Conundrum: This is often the primary suspect. Carburetors are intricate devices that mix air and fuel, and they're susceptible to clogging, especially if the ATV sits for extended periods. Old fuel can varnish and gum up the jets and passages. Solution: Start by cleaning the carburetor thoroughly. You can purchase carburetor cleaner spray and carefully disassemble the carb, cleaning each component. Pay particular attention to the jets and float needle. If cleaning doesn't work, a carburetor rebuild kit is a relatively inexpensive option. Also, always use fresh fuel and consider adding a fuel stabilizer when storing your Big Bear.
Spark Plug Problems: A fouled or worn spark plug can definitely make starting difficult. A weak spark means inefficient combustion. Solution: Remove the spark plug and inspect it. Look for signs of fouling (carbon buildup, oil, etc.) or wear. Clean the plug if it's just a bit dirty, but if it's heavily fouled or the electrode is worn, replace it with a new plug of the correct type. Make sure the spark plug gap is set correctly according to your owner's manual.
Weak Battery Blues: A weak battery simply can't provide enough juice to crank the engine over effectively. This is more common in older Big Bears or those that haven't been properly maintained. Solution: Test your battery with a voltmeter. A fully charged 12-volt battery should read around 12.6 volts. If it's significantly lower, try charging it with a battery charger. If the battery doesn't hold a charge or quickly drains, it's time for a replacement. Also, inspect the battery terminals and cables for corrosion and clean them thoroughly.
Valve Adjustment Issues: If your valves are out of adjustment, it can affect compression and make starting difficult. Too tight valves can prevent them from fully closing, and too loose valves can reduce valve lift. Solution: This requires some mechanical skill. Consult your service manual for the correct valve clearance specifications and the procedure for adjusting the valves. If you're not comfortable doing this yourself, take it to a qualified mechanic.
Compression Concerns: Low compression means the engine isn't sealing properly, which hinders the combustion process. This can be caused by worn piston rings, valve problems, or a damaged cylinder. Solution: A compression test will reveal if you have a compression problem. You'll need a compression tester, which is relatively inexpensive. If the compression is low, further diagnosis is needed to pinpoint the cause. This might involve a cylinder leak-down test.

My Big Bear is Losing Power! What Could It Be?

A loss of power can be frustrating, especially when you need that extra oomph to tackle a tough trail. Here are some common reasons why your Big Bear might be feeling sluggish:

Clogged Air Filter: A dirty air filter restricts airflow to the engine, leading to a loss of power. It's a simple but often overlooked issue. Solution: Inspect your air filter regularly and clean or replace it as needed. A clean air filter is crucial for optimal engine performance.
Fuel Delivery Problems (Again!): Similar to starting issues, fuel delivery problems can also cause a loss of power. A partially clogged carburetor jet or a weak fuel pump can starve the engine of fuel. Solution: Revisit the carburetor and fuel system. Ensure the fuel filter is clean and the fuel pump is functioning correctly. You can test the fuel pump output by disconnecting the fuel line and cranking the engine (be careful not to spill fuel).
Transmission Troubles: In some cases, a problem with the transmission can cause a loss of power. This could be due to worn clutch plates or other internal damage. Solution: Listen for any unusual noises coming from the transmission. If you suspect a transmission problem, it's best to take it to a qualified mechanic for diagnosis and repair.
Exhaust Obstructions: A blocked exhaust system can restrict the flow of exhaust gases, reducing engine power. This can be caused by a clogged spark arrestor or damage to the exhaust system. Solution: Inspect the spark arrestor for carbon buildup and clean it if necessary. Check the exhaust system for any dents or damage that might be restricting airflow.

The Brakes on My Big Bear Are Squealing! Help!

Squealing brakes are not only annoying but can also indicate a problem with your braking system. Here's what to consider:

Worn Brake Pads: This is the most common cause of brake squealing. As the brake pads wear down, they can start to make noise. Solution: Inspect your brake pads for wear. If they are thin or worn unevenly, replace them with new pads. Remember to replace the pads on both sides of the ATV at the same time.
Contaminated Brake Pads: Oil, grease, or other contaminants on the brake pads can cause them to squeal. Solution: Clean the brake pads and rotors with brake cleaner. If the contamination is severe, you may need to replace the pads.
Glazed Brake Pads: Overheating can cause brake pads to become glazed, which can lead to squealing and reduced braking performance. Solution: Lightly sand the surface of the brake pads with sandpaper to remove the glaze. If the glazing is severe, you may need to replace the pads.
Worn Brake Rotors: Worn or damaged brake rotors can also cause squealing. Solution: Inspect the brake rotors for wear, cracks, or warping. If they are damaged, replace them.

My Big Bear's Overheating! What Should I Do?

Overheating is a serious issue that can cause significant engine damage. Here's what to check:

Low Coolant Level: The most obvious cause of overheating is a low coolant level. Solution: Check the coolant level in the radiator and overflow tank. If it's low, add coolant to the correct level. Be sure to use the correct type of coolant for your Big Bear.
Clogged Radiator: A clogged radiator can restrict coolant flow and cause the engine to overheat. Solution: Inspect the radiator for dirt, debris, or mud. Clean the radiator fins with a soft brush and water. You can also use a radiator flush to clean the inside of the radiator.
Faulty Thermostat: The thermostat regulates the flow of coolant through the engine. If it's stuck closed, it can prevent coolant from circulating properly and cause overheating. Solution: Test the thermostat to see if it's opening and closing properly. You can do this by placing it in a pot of hot water and observing whether it opens. If it's not working correctly, replace it.
Water Pump Problems: The water pump circulates coolant through the engine. If it's not working properly, it can cause overheating. Solution: Check the water pump for leaks or damage. If you suspect a water pump problem, it's best to take it to a qualified mechanic for diagnosis and repair.

Electrical Gremlins! My Lights/Display Aren't Working!

Electrical problems can be tricky to diagnose, but here are some common issues and solutions:

Blown Fuses: This is the first thing to check when you have an electrical problem. Solution: Locate the fuse box and inspect the fuses. Replace any blown fuses with fuses of the correct amperage.
Loose Connections: Loose or corroded electrical connections can cause a variety of problems. Solution: Inspect all electrical connections for looseness or corrosion. Clean the connections with a wire brush or electrical contact cleaner.
Faulty Wiring: Damaged or frayed wiring can cause shorts or open circuits. Solution: Inspect the wiring harness for any signs of damage. Repair or replace any damaged wiring.
Bad Switch: A faulty switch can prevent electrical components from working properly. Solution: Test the switches with a multimeter to see if they are working correctly. Replace any faulty switches.

Frequently Asked Questions

Why is my Big Bear backfiring? Backfiring is often caused by a lean fuel mixture or an exhaust leak. Check the carburetor and exhaust system.
How often should I change the oil in my Big Bear? Refer to your owner's manual, but generally, every 100 hours of operation or annually is recommended.
What type of oil should I use in my Big Bear? Use a high-quality ATV oil that meets the manufacturer's specifications. Check your owner's manual for the recommended oil type and viscosity.
My Big Bear won't shift into gear. What's wrong? Check the shift linkage for damage or adjustment issues. Low transmission oil can also cause shifting problems.
How do I store my Big Bear for the winter? Clean the ATV thoroughly, change the oil, stabilize the fuel, and disconnect the battery. Store it in a dry, covered location.

Keeping Your Big Bear Bear-ing Up!

The Yamaha Big Bear is a tough and reliable machine, but like any vehicle, it requires regular maintenance and occasional repairs. By understanding the common problems and their solutions, you can keep your Big Bear running smoothly and enjoy many years of trouble-free riding. Remember, regular maintenance is key to preventing many of these issues from arising in the first place.