Review: 2007 Yamaha Big Bear 400 IRS 4X4

Time To Get Dirty

Dec. 03, 2006 By Ricky Sosebee

2007 Yamaha Big Bear 400 IRS 4X4


A specially developed ATV has been built by the Yamaha Corporation. The crowd they have targeted is a little dirty.

After researching the central and southeastern end of the United States Yamaha has found that a desire to go "Muddin" is what really excites their target audience. The Custom Built Big Bear 400 is engineered to fill that desire.


The 2007 Big Bear 400 is not only a solid machine for jobs around the farm but it can also get down into some places that most wouldn't dare to venture. To prove to the media that its built for the tough stuff Yamaha took a group of Journalists to the Dirty Dog Off-Road Park way down in Phenix City Alabama. This would definitely put the new Big Bear to the test. Miles and miles of trails waited just off the main parking area and it seemed to call out as we parked out near the Yamaha rig. With fifteen or so brand new Big Bears waiting I was ready to get started. A good once over revealed the simplicity of the Big Bear. The styling was simple and many features have been placed just so that the average mechanic could maintain his own ATV and without expensive diagnostic equipment. There is a lot to see so lets get to it.


The United States has several unique areas that make up the vast majority of this Big Bears market. Did you know that the 5-speed air-cooled four by four ATV's make up twenty five percent of the total sales of 4x4 atvs? And did you also realize that 50% of those sales are in states along the southeastern United States. This is where swamps and low-lying creek flooded farmland will make the Big Bear shine. Yamaha's Newnan Georgia facility is in the heart of this prime workhorse atvs element.

The three hundred eighty six cubic inch motor is air cooled for a few reasons. The facts are that liquid cooled motors have issues when it comes to playing in the wet stuff. If the radiator becomes clogged it will cause over heating issues that can finish off the average ATV. But the Big Bear designers had a simple fix for that and it is the air-cooled engine. There is still the oil cooler to deal with but it has been relocated to get it up behind the protection of the front fenders in the nose of the Big Bear. The oil coolers capacity has also been increased by thirty percent which not only gives the reserve oil needed to keep the motor running clean but it also makes for lower engine temperatures and better performance. So the reality is that Yamaha has built the Big Bear to almost Tank like specifications. Everything vital to the quad is protected.


The engine of the Big Bear 400 breathes through a 33mm Mikuni Carburetor. The guys at Yamahas engineering facility could have easily been drawn by the temptation to sling one of their famous EFI or Electronic Fuel Injection units on this quad. But to keep with the plan of the simple serviceable unit they opted for the traditional carb. This would allow the rider to maintain things himself, even on the trail. If you get water in your fuel, and sometimes it happens, you just drain the carb bowl with a simple turn of the screw on the bottom of the carb and get back to riding. Remember this, the Big Bear is simple and we found that out with every feature. So from the carb to the cylinder of the Big Bears 386cc engine the fuel is fired by a standard DC-CDI ignition system The 8.6:1 compression should allow for easy starts and smoother running. Not to mention it adds reliability to the life of the Big Bear.

The motor is then fired with a standard DC-CDI ignition. The electrical components on this Years Bear have been upgraded to Marine style components. These plugs and wiring systems can be submerged in water and still remain dry where it counts. This has to be the feature that all utility ATV's should be built with from the factory. If it's built to get wet and dirty then it has to be safe and that's where Yamahas engineers didn't pass the buck.


To start the Big Bear you have two choices. The first is the electric start, which is just a touch of the button located on the left handlebar mounted control center. But lets say you happen to like a more MANLY starting operation. Then you can pull till your hearts content on the rope style pull start located on the lower left side of the engine just about at your ankle. I prefer the electric start myself but just for the experience I had to try the pull start just once. I have to say that it was an easy pull and it fired right up the first time. That's a great feature especially if the Yamaha Big Bear is going to hunting camps all over the southeast. Its does get cold down here and although the maker of the battery wants it to perform in any condition it will run down or just be plain lazy sometimes in colder weather. That is where this feature will be envied by others without it.

Once the engine is fired up you have five gears and a reverse that can be a lifesaver when you're stuck. The first gear is a little low for me but in understanding the purpose for what the Big Bear was built it seems to fit right in. I have had granny gears in old Chevy trucks before that this low down first gear would put to shame. I am guessing that if you had to pull a competitors ATV out of the mud this would be the gear to do it with. Once the quad is moving I think second is possibly the most usable gear for getting the Big Bear rolling. The transmission has an automatic clutch which allows you to stay focused on the trail and hold onto the Big Bear. This not only eliminates costly maintenance of the clutch system, which in the mud can be a regular task, it also makes the operation just a bit more simple. There is also engine breaking which most other manufacturers charge extra for and Yamaha gives you for your safety. The other braking options that are included are the front dual hydraulic disc brakes and on the rear you have a new feature in the sealed oil bathed 5 disc braking system. Look for the feature Tech article on that gets to the ideology of this system.


Yamaha has put it's On-command push button 3-way locking differential at your right thumb to get you into and out of the tough spots. The button is unique in that it has a few different operations. Pressing the 4x4 button in allows a somewhat limited slip feature. This seems to be all the Yamaha Big Bear needs in the deep stuff but if you really get down into the hardcore "man I didn't see that coming" mud you can simply rotate the long lever over the 4x4 button and press the yellow button so its out and this locks the differential full on. This feature makes the Big Bear unstoppable in most any condition. All of the Big Bears power is transferred to the wheels by drive shafts and they all have protective booting to keep the trash out.


The suspension on the new Yamaha Big Bear 400 is independent double wishbone front and rear that makes the riding in uneven terrain a breeze. This Bear has 10.5 inches of maximized ground clearance so deep ruts pose little threat. The shocks that suspend this Bear are 5-way preload adjustable and can also be adjusted on the trail for the discriminating rider. The Big Bear seemed to handle easy and there is little feedback in the steering when encountering roots and rougher terrain although I would recommend a steering stabilizer for the Big Bear just to make sure your always in control.

Did I mention that the Big Bear comes from the factory with aftermarket shoes already mounted on the rims? The front tires are 25x8-12 and the rear's are 25x10-12 this helps with the end ground clearance as well. It seems the folks at Yamaha want to give you everything you need and make sure that when you leave the dealer floor you are for certain to take the new Big Bear right to the trails without waiting on any parts. ITP developed the MudLite for the trail user who likes getting into mud and creeks without getting stuck. They also made the MudLite to be gentle on you over rough terrain at low speeds by softening out the side wall of the tires. The end result is a tire that's comfortable for any rider and gets up and over most any obstacle.

The Big Bear 400 has to be the simplest ATV I have seen yet. It comes ready to rip up the trail and with so many features from the simple speedo to the intergrated floor boards to keep the mud off of your boots. Of course this only works if you don't get into the deep stuff then you might want to grab a set of waders. The colors for this year will be Hunter Green, Steele Blue and Red. This years Big Bear has Dual 30watt Krypton Multi-reflector headlights for those early trips to the deer stand also. The improvements over last years model are totally noticeable and will make the Big Bear a stand out competitor in the woods and mud.


And just when you thought that this Yamaha Big Bear was finished it will also come in an "Exploring Edition" which will include extras like Oversized fenders for even more mud protection, rear rack extender with a front rack bag and plastic hand guards. All of this will be offered on the Steele Blue Big Bear 400 in dealerships around December. This is most defiantly a purpose built quad but the farmhands around the south and anywhere for that matter will be playing in the late evening when the work is all done. Get yourself some fun and make it happen with the new Yamaha Big Bear 400.


2007 Big Bear 400 IRS 4X4

Engine Type - 386cc, 4-Stroke Single, Air/Oil Cooler w/ Fan, SOHC

Bore x Stroke - 83mm x 71.5mm

Compression Ratio - 8.6:1

Carburetion - Mikuni 33mm BSR

Ignition DC ? CDI

Starting System - Electric w/ Auxiliary Pull

Transmission - 5-Speed Automatic Clutch w/ Reverse

Engine Braking - Fr. & Rr. Wheel

Drive Train - Yamaha On-Command push button 3-way locking differential, 2WD, 4WD, locked 4WD; Shaft

Suspension/ Front - Independent Double Wishbone, 5.8? w/ 5-way Preload Adjustment.

Suspension/ Rear - Independent Double Wishbone, 7.6? w/ 5-way Preload Adjustment

Brakes/ Front - Dual Hydraulic Disc

Brake/ Rear - Fully Sealed , Oil Bath, Multi Disc

Tires/ Front - ITP Mud Lite 25x8-12

Tires/ Rear - ITP Mud Lite 25x10-12

LxWxH - 79.4"x 43.9"x 46.7"

Seat Height - 35.2"

Wheel Base - 48.4"

Turning Radius - 126"

Ground Clearance 10.5"

Fuel Capacity - 4.0 Gallons

Dry Weight - 593 Lbs

Rack Capacity - 88 Lbs.Fr. / 176 Lbs. Rr.

Towing Capacity - 904 Lbs.

Instrumentation - Speedometer / Odometer & Fuel Gauge

Lighting - Dual 30W Krypton Multi-reflector Headlights & 21/5W Brake light Newsletter
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