Only those who have been hiding under a rock haven’t heard all the commotion about Yamaha backward engines, wrap-around pipes and gas tank-style airbox. Perhaps the best guy to ask about aYamaha is Dr. D.D. Doug Dubach knows Yamahas better than anyone on the planet. Not only was he a Team Yamaha factory rider, but he is also their official test rider and the owner of the aftermarket exhaust company DR.D. He is clearly the go-to guy when it comes time to iron out the wrinkles on a 2014 YZ450F.
In stock trim, the YZ450F has the most powerful engine in its class. At just over 58 horsepower and armed with a hard midrange hit, the YZ-F engine has more than enough pony power for anyone who swings a leg over the saddle. But—and there is always a but—for the majority of the MXA wrecking crew, the stock YZ450F powerband was too abrupt off the bottom. It felt jerky at tip-in and needed a more unified transition into the midrange. We wanted a more usable powerband off the bottom and an easier-to-ride transition from the low to the mid—and that is exactly what DR.D gave us.
You may be wondering how we can complain about a powerplant that pumps out so much horsepower, but until dynos go to the starting line in place of riders, dyno numbers can’t tell the whole story. Doug understood our complaints and knew that the power didn’t need to be increased, just moved around to make it broader.
THE DR.D ENGINE PROGRAM
DR.D started the modification project with three basic steps.
Exhaust: Obviously, Doug based the YZ450F project bike on his wraparound DR.D NS-4 exhaust system. It broadens the power and makes the power feel torquey across the range.
Throttle body: Doug installed an Injectioneering throttle body mod to the YZ450F’s fuel injector. This reshaped butterfly valve is well-respected for its ability to liven up the throttle response and bottom end of any fuel-injected bike. The Injectioneering throttle body made for a smoother transition into the midrange. It took a few laps to get used to the new feel, as there was no turbo lag at the crack of the throttle, but we loved what the Injectioneering throttle body did to the powerband.
Mapping: The final adjustment was to fine-tune the mapping. Although DR.D builds its YZ450F exhaust system to run with the stock map, MXA has extensive mapping experience on the 2014 YZ450F, and we felt we could get more power with the addition of richer fuel maps (we did not change the ignition map). During the mapping sessions, we employed three test riders, including Doug himself, and within two maps we cleaned up the jetting and increased power for a crisper feel.
The exhaust pipe, Injectioneering butterfly, and 3-percent-richer map on the bottom and mid (six-percent richer on top) were the only engine mods made on the DR.D YZ450F. That was it! MXA test riders are usually begging for more power, but technology has advanced enough that instead of looking for more power, we are trying to massage the available power into a more usable profile.
WORKING ON THE CHASSIS
With Yamaha’s new design and the emphasis on centralization of mass, the YZ450F’s handling is much improved over the rather atrocious handling of the 2010 through 2013 YZ450Fs. The Yamaha engineers made major upgrades to the YZ450F handling, but there are still remnants of the previous model’s peccadilloes—they just aren’t as severe. In a nutshell, the YZ450F is loose going into corners and, when combined with the barky low end, this trait makes it hard to get low and stay down while turning.
The first thing we did to improve the handling was to install a DR.D radiator lowering kit, which moved the water weight down a significant 24mm. Step two was to change the triple-clamp offset from 22mm to 20mm with an Applied triple clamp. The combination of the lower radiators and increased trail allowed the bike to settle into the corners, making the YZ450F more of a point-and-shoot machine. Step three was to work on the balance of the chassis to get the bike to feel level. This gave riders more confidence; they could flow from corner to corner without having to fight the bike.
THE SSS SUSPENSION PACKAGE
As far as the suspension goes, it is hard to top Yamaha’s stock Kayaba SSS suspension. Nine times out of 10 you can find a good setting with just a careful adjustment of the sag and a few clicks. Doug has always raced with Enzo suspension, so he sent the SSS components to them to fine-tune the feel for our weight and speed.
Strangely, there was an elastomer bumper mounted under the swingarm to function as a top-out device for the rear shock—something we haven’t seen since Tony Cairoli raced for Yamaha several years ago.
The MXA test riders liked the rear end but felt that the front forks were very harsh from the midstroke down. We clicked out on the compression and rebound, and that worked well with Enzo’s plusher initial stroke and ramped-up midstroke. Once dialed in, the forks were fluid in the small chop and stiff in the big hits.
What else could we asked for? Without going to the added expense of cracking the engine open, DR.D addressed MXA’s major complaints about the stock YZ450F setup, and DR.D will be more than happy to point you in the right direction too. For more information, go to www.dubachracing.com or call Dubach Racing & Development at (877) 382-2241.