Imagine if you can, a forest fire so great, that it has been burning for ten months and is continuing to spread. It all started when a burning torch, Honda's 400EX--was placed to a fire-prone, dried up grassy field--the sport ATV market. The flame spread like wildfire and engulfed the grassy fields in minutes, swiftly moving on to the forest (aftermarket companies) which has provided the fire with ample fuel to burn vigorously for these past ten months. That's how the ATV market is burning since the consent decree expired. It's common knowledge that there is a frantic rush among aftermarket companies to claim the crown "King of Power" by extracting the most horsepower out of the 400EX. We were recently contacted by performance leader FMF, asking if we'd be interested in their Power Core IV exhaust system. After a short pause, while the smiles formed on our face, we gladly accepted.

The Product:
      The PowerCore IV exhaust system is a new addition to FMF's four-stroke product lineup. FMF claims the non-corrosive nickel- plated PC IV system dramatically improves low to mid range power. It's completely rebuildable and spark arrestor legal. Another nice feature for the weight-conscious rider is the PowerCore IV is 4.5 pounds lighter than the stock 400EX exhaust pipe. The super-high exhaust flow and roar of the Power Core is immediately recognizable as a performance-oriented pipe. Please keep in mind while riding that this pipe is loud. Try your best not to disturb other trail users.

Installation:
   The installation procedure for the PowerCore IV on the 400EX is simple, requiring only 10mm and 12mm sockets. The first step is to slip the pipe snugly onto your existing header and insure there is no binding of the two pieces. Attach the new mounting bracket to the quad frame and place the muffler clamp where the header pipe slides into the Power Core. Tighten the muffler clamp (Do not overtighten) first, then the bolts holding the Power Core onto the mounting bracket.
   

Extra Goodies:
      Many riders who upgrade their machines with aftermarket exhaust pipes have discovered it's best to rejet the carburetor to obtain optimal running conditions from their machines.       We installed a jet kit from the guys at DynoJet. The kit came with eight different jet sizes, and a main jet adapter. Also included is a new style fuel needle. The new fuel needle allows easy adjustment for elevation through the adjusting washer and E-clip. Dynojets detailed instructions allow you the option of a Stage I or Stage II settings. Stage I is just the dyno jet kit alone, while Stage II goes to the extreme and adds a bigger jet size to handle other modifications such as the pipe, airbox and air filter mods. Also provided, are recommended jet sizes and fuel mixture screw settings to go along with the different after market exhaust, air box mods and air filter upgrades. The DynoJet kit was a real asset to our modified 400EX.

Evaluation:
      Now that the PowerCore IV is installed and ready to go, we're ready to rock! Once the 400EX was fired up, the deep throaty roar of the PowerCore IV gave a sense of power increase. The pipe-modified 400EX even shocked us when compared to the stocker. The performance increase was outstanding. The PowerCore IV in combination with the DynoJet Kit gave the 400EX instant and strong acceleration throughout the powerband. The aggressive rider who likes to "hammer down" on the throttle, will find the front end climbing skyward while rapidly shifting through the gears. This sensation gives the rider a new addiction to this machine. However, one should not get the wrong impression, this wild stallion can still be ridden recreationally, with snappy power on standby. Even our experienced test riders returned with smiling faces and pounding hearts. It was literally a new machine when compared to its stock form.
   

Test Ride:
      Since we didn't have two 400EXs handy, our test rides consisted of time trial evaluations. We tested the pipe on a flat, grassy field measuring 150-yards. The test included two test riders given six rides each, three on the stock machine, and three on the modified 400EX. The best time went to the FMF/DynoJet modified 400 which was a consistent winner with either rider in control. The modified 400EX ran the 150-yard distance in 7.9 seconds, with the stock 400EX's 150-yard 1.9 seconds behind at 9.8. Our best guess is this difference in time will result in about a four quad length distance difference in side by side racing.

Conclusion:
     We absolutely loved riding this hopped up 400EX. The increase in horsepower and throttle response was amazing. Our subjective seat-of-the-pants tests showed the pipe-modified EX to be clearly faster than a stock machine. If you're interested in making the same modifications to your 400EX, here are the modifications to the Connection's 400EX. In addition to the PowerCore IV pipe and DynoJet jetting kit (170 main jet), we installed a K&N air filter with prefilter, and drilled six 1.5-inch holes in our airbox lid. Once again, these modifications really wake up the 400EX and make it run super-strong. __