MOD QUADS: HINSON YFZ450

HINSON YAMAHA YFZ450R
      In the August print issue of Dirt Wheels, our modified 450 MX shootout was a massive project that involved six ATVs built by six different companies. The object of the test was simple: we compared the quads in full-race form. The only limit was that they all had to represent a similar investment; somewhere in the $15,000 range including the initial purchase price. To give you a little more detail on each of the projects, we’ll be featuring the machines one at a time on the web over the next few weeks.
      Yamaha rocked our world last year when the YFZ450R came out. It was already track width, it was fuel-injected and it had a high-tech aluminum frame. Finally, we had a machine to take on the Suzuki in terms of being race-ready.
Now that we have lived with the machine for over a year, we have a clearer view of its place in the big picture. We love it as much as ever, but can objectively see where it needs to be improved. Hinson Racing spent most of the year testing with Adam Campbell to develop our test machine for this shootout.
      The Yamaha starts off with a fairly steep price. It’s a good thing that so much of the work was already done. We didn’t need a wider axle or extended A-arms. But we still wanted to target handling above all else. We have noted a slight twitchiness in the YFZ’s cornering manners--perhaps not as bad as the Kawasaki’s, but notable nonetheless. We addressed it with Houser Racing’s TricTrac kit. This is a system that alters the caster as the front suspension is compressed--many of the top Yamaha Pros use it, including Bill Balance in the GNCC series and Pat Brown in motocross. Unfortunately it can only be used on Houser Pro Series A-arms, and we hadn‘t planned on replacing the A-arms. We compromised by replacing only the top A-arms, an option that took a little work. This is where the testing came in--it took days to set up the front end properly.
      Another issue that Yamaha riders complain about is the harsh lash between open and closed throttle. The EFI system has a somewhat jerky transition between on and off. If ever there seemed a good application for the Hinson BTL slipper clutch, this is it. Engine braking could be greatly reduced by the one-way slippage of the clutch, and the harsh engine lash would be less of a factor.
      That left little budget for motor mods. We settled on a Yoshimura stainless steel exhaust and a PIM 2 engine management system. A GYTR air filter kit allowed the motor to breathe better. GYTR also was represented with nerf bars, and the Yamaha comes stock with a Pro Taper handlebar (way to go!).
      The rest of the quad got the same modifications as the others. The Fox Float Evol front shocks and Podium X rear shock, and DWT wheels and tires. For the damper on this unit, we selected the Precision Pro Series.