Yamaha YFZ450R MX Project - Part 1

Building an A Class killer

Story by Jeff M. Vanasdal, Photography by Josh Petry, Jul. 21, 2010
 

As ATV.com’s resident sport quad aficionado, we’re always excited when a manufacturer comes out with something new. When Yamaha introduced its YFZ450R for the 2009 model year we were extra stoked as we’d been racing on the original YFZ450 for several years.

We were lucky enough to be one of the first to have tested the YFZ450R when it was first introduced. We’ve ridden it out in sand dunes in Southern California and on numerous motocross tracks, but we’d never really had a chance to enter it into real race settings. That’s all about to change.

Yamaha recently loaned us a 2010 YFZ450R for some long term testing and we’ve decided to jump on the opportunity and use the YFZ for a motocross project.  This article will mark the first of a series on racing and modifying the 2010 Yamaha YFZ450R to be competitive in the local AMA district 15 MX in the A Class.

Before we go about procuring parts and modifying our project quad, we entered the stock YFZ450R into the A Class at local MX race to see how it performed out of the box. To our surprise it did very well considering all of the competitors had outfitted their race quads with aftermarket exhausts, suspension, and other components.

Yamaha built the YFZ450R to be a competitive machine right off the showroom floor. With its wide 48.8-inch wheelbase the YFZ has an stance that is made for racing motocross, which is a distinct advantage over many older model ATVs. Before manufacturers started making motocross-width ATVs you had little choice but to buy aftermarket extended A-arms in you wanted to be competitive.

We plan on entering the YFZ450R at many more local races as we build it up to be a top dog local A Class machine. However, to be truly at the top we do need to modify our stock YFZ just a bit. The aftermarket is absolutely littered with parts for the YFZ450R and it can be a little intimidating trying to figure out what changes to make. Just because it’s out there doesn’t mean you need it. Many times we’ve seen guys show up at a local MX race with a full set up and they are first year racers or race in the B Class – more often than not it’s overkill. With this build we want to stick with a reasonable budget and still be able to consistently be in the five in the A Class.

We feel pretty confident that our bone stock YFZ450R is capable of winning some races, but maybe not in the A Class. Our job here is to formulate a plan that will get the YFZ450R to the top step of the podium.

Perhaps the most obvious change we need to make is the tires. Changing the tires is the easiest way to improve lap times and we think it will make a huge difference for our project quad. Yamaha outfitted the YFZ with tires are a little bigger than you’d normally want for motocross racing. They’re fine for having fun on the track and riding the trails, but we plan on replacing the stock rubber with something a bit more aggressive and specific to motocross.

We also plan to bump up performance by adding an aftermarket exhaust. This should provide a bit more power from the bottom end and will be easier to lift the front. Hopefully this will also give us an extra burst to get out the corner quicker. A faster bottom end means more power to clear jumps especially on a tight or technical track. The track we raced on featured two tabletops, whoop section, step up, double and a short rhythm section. Although this was considered to be a novice track it proved to be quite challenging when we wanted to be smooth and clear all the jumps on our stock ATV.

The stock YFZ450R has plenty of power to get around the track, but in the straights and out of tight corners we wouldn’t mind seeing a slight improvement in throttle response. The straights were where we lost some ground to other competitors in our class with built-up motors. We’re hoping that by adding an exhaust we will gain some ground in the straights and improve our bottom end out of the hole.

As for handling, we found the YFZ450R to be very easy to control on the ground and in the air. It is an easy machine to throw around and it corrects well in flight. Handling is dead on and predictable. Although some of the jumps on the track, notably the rhythm section, required us to seat bounce the quad to get over. Fortunately, the YFZ450R is light enough and the stock shocks work well enough that we could safely make it to the landing.

We also came to appreciate the fuel injected engine, because it’s awfully nice to never have to mess with carburetor jetting. On the day of the race, several carbureted Honda 450Rs were having problems getting their jetting right due the humidity in the air. This was a major issue for them as some ended up stuck in the pits and never made it out on the track.

The YFZ450R has a totally different feel than the older carbureted version. The fuel injected engine has much smoother power than its predecessor, which had a snappier powerband. Even though the power on the modern YFZ is not as responsive, it is there in plenty, even in stock form.

Though certainly not key to performance, the YFZ450R is a pretty good looking quad and a lot of people were checking it out in the pits. Yamaha did a nice job designing the new YFZ with its sharp lines of the plastic and aggressive styling. We really enjoy Yamaha’s initiative in making plastic that helps in reducing rider fatigue, which is the idea behind the black plastic that flows down the sides by the rider’s thighs/knees.

As much as we like the overall look, the stock graphics are a little small for our tastes. We plan on sprucing up the YFZ a bit with our own Santor Design Co. graphics kit.

Other changes we plan on making include the addition of a front bumper and rear grab bar. This will not only bring some style to the YFZ, but the grab bar and front bumper will offer some additional protection.

Be on the lookout for our next article on our Yamaha YFZ450R Motocross Project as we start to add additional parts in the weeks to come!

Related Reading
Yamaha YFZ450R MX Project - Part 2
Yamaha YFZ450R MX Project - Part 3
Yamaha YFZ450R MX Project - Part 4
2009 Yamaha YFZ450R Review
2009 Yamaha YFZ450R Review - Dune Test
2010 Yamaha YFZ450R and Raptor 700R SE Review
2008 Yamaha YFZ450 Project
Yamaha Raptor 250 Project - Overview