Discover the Unstoppable Yamaha Big Bear 350 – Power and Performance

Introduction to the Yamaha Big Bear 350

In the world of all-terrain vehicles, four-wheelers have become a favored choice among outdoor enthusiasts. The Yamaha Big Bear 350, Yamaha’s entry into the 4×4 vehicle market, is a notable inclusion in this trend. Released in 1987 alongside other pioneering quads, the Big Bear 350 introduced consumers to class-leading technology at an affordable price point.

The Yamaha Big Bear 350 holds a distinctive place in history as Yamaha’s beginnings into 4×4 vehicles. It joined the ATV greats like the Honda FourTrax 350 4×4, the world’s inaugural 4×4 ATV. The Big Bear 350 featured a BST34 Mikuni carburetor, a dual-range 10-speed transmission, and the Torque Control Differential (TCD). Yamaha produced it from 1986 to 1998, and it became a staple in the ATV scene for 13 years before making way for the Yamaha Big Bear 400 4×4 in 2000.

Yamaha Big Bear 350

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Beginning of the Big Bear Series

The Yamaha Big Bear 350 served as the predecessor to a series of ATV models catering to diverse preferences. It highlighted three different trims across 13 model years, each presenting unique offerings. The constant appeal of the Big Bear resulted from its superior suspension and its utility as a hunting vehicle. It offered abundant storage space for riders’ essentials while journeying the trails. Some riders valued it as a full-time 4WD quad, while others preferred selectable driveline modes.

Maintaining a Big Bear in pristine condition requires regular maintenance. Meticulous care and attention to detail such as scheduled oil changes ensure the engine’s longevity and the overall lifespan of the vehicle.

Cost of a Yamaha Big Bear 350

The price of a Yamaha Big Bear 350 depends on the model year and trim. The primary 4WD model ranges from $2,365 to $4,000, and the 2WD version introduced in 1996, falls within the $3,000 range. In the Big Bear’s final production year, the HT Edition carried a price tag of $4,080. Pre-owned Big Bears in outstanding condition could fetch prices of $2,790 or higher if the quad remained in its original and mint condition.

Auction listings for Big Bears normally range from $750 to $9,300, with HT trims holding the highest value. These units usually have few previous owners and are predominantly used for yard work or hunting. Units valued above $3,000 often come with a rebuilt clutch and additional accessories like snowplows, gun racks, handguards, and winches. Cheaper listings are typically operational but might have cosmetic flaws like broken plastics, rusted utility racks, or lights requiring replacement.

Yamaha Big Bear 350 Specs & Features (1997 Model)

The 1997 Yamaha Big Bear 350 was powered by a four-stroke, air-cooled, single-cylinder SOHC engine. With an engine displacement of 348 cm³, a compression ratio of 8.6:1, and a wet sump lubrication system, this machine packed a punch. Its top speed was around 40 mph, depending on various factors like rider weight and terrain.

The estimated fuel economy was approximately 20 mpg, making it relatively fuel-efficient for its class. The engine output was 17.1 kW (23.2 PS) at 6,500 RPM. To keep the engine running smoothly, proper lubrication was essential, with oil capacity varying depending on the maintenance task.

Engine:

The heart of the 1997 Yamaha Big Bear 350 was its four-stroke, air-cooled, single-cylinder SOHC engine. With a bore-stroke ratio of 83 by 64.5 mm and an engine displacement of 348 cm³, it delivered a power output of 17.1 kW (23.2 PS) at 6,500 RPM. A wet sump lubrication system ensured the engine’s smooth operation.

Top Speed:

The Yamaha Big Bear 350 had a stock top speed of 40 mph, although this could vary based on factors such as rider weight, terrain, and vehicle condition. Under ideal conditions, it was possible to reach speeds of up to 45 mph.

Fuel Economy:

This ATV boasted an estimated fuel economy of approximately 20 mpg (11.8 liters/100 km). To keep the tank filled, it required 2.64 US gal (10 liters) of regular gasoline with a pump Octane number of 87+ and a research Octane number of 91+.

Lubrication:

The Big Bear had specific oil capacities, including 3.1 US quarts (2.9 liters) at draining, 3.7 US quarts (3.5 liters) at disassembly, and 3.2 US quarts (3 liters) at an oil filter change. It was recommended to use SAE 5W, 10W-30, or 20W-40 Yamalube 4 4-stroke oil or equivalent with an API grade of at least SJ for optimal performance.

Drivetrain:

Power was delivered to the wheels through a five-speed constant-mesh shaft drive and a wet, centrifugal automatic clutch system. The primary spur gear had a reduction ratio of 76/24 (3.167), with the first gear at 38/13 (2.923) and the fifth gear at 25/33 (0.758). The Big Bear’s 11.1-foot turning radius contributed to its agile handling.

Ignition:

The Yamaha Big Bear 350 featured a DC-CDI ignition system with an electric start and auxiliary mechanical recoil backup. It required a 12V, 14 Ah, 190-CCA (Cold Cranking Amps) battery. The spark plug specifications included NGKD8EA for U.S.-released models and NGKDR8EA for those released in Canada.

Tires:

The quad came equipped with tubeless Dunlop KT404 AT25 × 8-12 front tires and Dunlop KT405B AT25 × 10-12 rear tires mounted on panel wheels. The recommended tire pressure was 25 kPa for both front and rear tires.

Drivetrain and Ignition:

Power from the engine was delivered to the wheels through a five-speed constant-mesh shaft drive and a wet, centrifugal automatic clutch system. The Big Bear had an independent double-wishbone front suspension and a swingarm (mono-cross) rear suspension, providing 98.5 mm of front wheel travel and 104 mm of rear wheel travel. The vehicle’s steel frame, combined with these suspension components, offered a comfortable and reliable off-road experience.

The Big Bear’s ignition system was based on a DC-CDI setup with an electric start system and auxiliary mechanical recoil backup. The vehicle required a 12V, 14 Ah, 190-CCA battery for reliable starting. Proper maintenance, including choosing the right spark plug, was essential for smooth operation.

Tires, Brakes, and Dimensions:

The Big Bear 350 came with tubeless Dunlop KT404 AT25 × 8-12 front tires and Dunlop KT405B AT25 × 10-12 rear tires, mounted on panel wheels. The recommended tire pressure was 25 kPa for both front and rear tires, with caution against going below 3.2 psi or beyond 36 psi during tire maintenance.

The braking system consisted of a right-hand operated drum brake and a left-hand and right-foot operated drum brake, which served as an engine braking system. These brakes contributed to the quad’s safe operation on various terrains.

In terms of dimensions, the Big Bear measured 76.6 x 43.1 x 45.9 inches (L x W x H) and had a minimum ground clearance of 9.65 inches. The vehicle’s wheelbase measured 48.7 inches, and it had a curb weight of 259 kg (571 lbs). The seat height stood at 32.9 inches, providing a comfortable riding position for users.

Capacities and Exterior:

The vehicle had specific oil capacities for its final gear case and differential gear case. The Big Bear 350 could carry a maximum load of 463 lbs (210 kg) when factoring in cargo, trailer hitch, vertical load, rider weight, and accessories. The horizontal load limit was 904 lbs (410 kg), while the vertical load limit was 33 lbs (15 kg).

The Big Bear’s exterior featured a steel tube frame, which offered durability and support. It also incorporated plastic body materials and various standard components like hand grips, front and rear fenders with splash guards, footpegs, front and rear bumpers, and utility racks. Lighting on the vehicle included two 25-watt headlights, a 7.5-watt tail/brake light, and 3.4-watt indicator lights. Some riders opted to convert these lights to LED for improved visibility.

Known Issues with the Yamaha Big Bear 350

Like any vehicle, the Yamaha Big Bear 350 had its share of known issues. One common problem was related to the front brakes, which could squeeze right into the handlebar. Addressing this issue typically required a master cylinder rebuild kit, available from dealers, to fix the problem.

Another concern revolved around the transmission. While the Big Bear 350 was a reliable machine with a stock top speed of around 40 mph, attempting to modify it for higher speeds could lead to transmission problems or failure. These modifications should be approached with caution.

Intermittent backfiring was another issue that riders encountered, which often stemmed from problems like a dirty carburetor, solenoid issues, or wiring problems. Cleaning the carburetor with a product like Seafoam often resolved this problem, but more serious cases might require a thorough carburetor inspection.

Torque issues, such as a decrease in torque after riding for a few minutes, were also reported. If the engine and electrical components were in good condition, consulting a mechanic for further assistance was recommended.

Front Brake Problem:

One common issue with the Big Bear 350 was related to the front brakes squeezing into the handlebar. If there were no fluid leaks and bleeding the brake lines didn’t resolve the problem, rebuilding the master cylinder was necessary. Dealers typically offered master cylinder rebuild kits with everything needed to complete the task.

Giddy Transmission:

Modifications intended to increase the quad’s speed could lead to issues with the transmission. The Big Bear 350 was designed for a maximum stock speed of around 40 mph. Attempting to push it beyond this limit could result in transmission damage or failure.

Intermittent Backfiring:

Intermittent backfiring was often attributed to issues such as a dirty carburetor, solenoid problems, or wiring issues. Cleaning the carburetor with a product like Seafoam could help, and if the problem persisted, the owner’s manual could serve as a reference for checking the wiring.

Torque Issues:

Torque issues, such as a decrease in torque after a few minutes of riding, were not uncommon. Factors like a dysfunctional spark plug or a cracked or sticky float bowl could cause this. Inspecting the engine and electrical components was essential, and if no issues were found, consulting a mechanic for further assistance was advisable.

Other Problems and Tips:

Other minor complaints included insufficient power, which could often be addressed through jetting to free up the machine’s power production. The issue of a glowing exhaust could be mitigated by using the right oil.

Putting the Big Bear in Reverse:

Shifting the Big Bear into reverse sometimes presented difficulties for riders. However, following a set of steps that included engaging the rear brake and releasing the throttle lever could help users shift into reverse safely.

About Yamaha

Yamaha, a company founded in 1887 in Shizuoka, Japan, initially specialized in manufacturing pianos and reed organs. After World War II, Yamaha transitioned into the production of motorcycles. In 1955, it separated from its parent company and became Yamaha Motor Co., Ltd. The company expanded its offerings to include all-terrain vehicles in the 1980s, establishing itself as a key player in the industry. Today, Yamaha produces a wide range of vehicles, including off-road vehicles, personal watercraft, speed boats, and outboard motors, with the Yamaha Big Bear 350 4×4 being one of its notable contributions.

Conclusion – Yamaha Big Bear 350 4×4

While the Yamaha Big Bear 350 4×4 may not have been the fastest or the most high-tech quad on the market, it remains an excellent and well-engineered off-road machine. With a top speed of around 40 mph, a substantial payload capacity, and the ability to tackle a full day of trail riding or heavy work, the Big Bear 350 is a reliable workhorse. It may not be a speed demon, but it is more than capable, making it an excellent choice for off-roading enthusiasts.

In conclusion, the Yamaha Big Bear 350 4×4 offers a blend of durability, utility, and reliability that has allowed it to carve a special place in the hearts of ATV enthusiasts. Whether you’re exploring the trails or taking on tough outdoor tasks, the Big Bear 350 has demonstrated its worth as a dependable companion for adventure and work alike.