Strictly MX: ATV Rider 450 Race Development

Way back in our September 2004 issue, we compared the Honda TRX450R and the Yamaha YFZ450 with some factory go-fast parts on them. The verdict? The YFZ's advantage (April '04 ATVR) over the 450R grew from an edge to a gap. The TRX was still its same mild-mannered self, but with a bit more beans; while the Yamaha became a fire-breathing (yet civilized) monster, begging to be raced. Not to deny the Yamaha its wish, and not to leave the Honda out, we started a quest to make them both the best MXers they could be. We chose to develop them specifically for motocross, because to make an uncompromised MX machine you have to give up some capability in other areas; and there are a slew of moto races in Southern California for us to check out: ITP QuadCross, Thunder in the Valley and the Douglas Wheels series, not to mention the GNC season opener in February at Glen Helen.

To take these machines to the next level, we had a couple of our resident fast guys adopt them: Photographer Adam Campbell made space for the YFZ in his garage, while Publisher Sean Finley took on the 450R. Both are former pro racers, and while Finley has a bit more pedigree (having been a factory rider for Kawasaki and Yamaha in the 1980s), Campbell has more recent experience with wins in local Vet class (30+) races and a White Brothers 4-Stroke Championship a couple of years ago.

We sent the pair their separate ways for their initial outfitting--Campbell's Yamaha to CT Racing and Finley's Honda to Goldenwest Cycle. As the YFZ was already out front, we decided to keep the transition mellow, making only those mods we knew it would need to compete on the track. Surprisingly, the Yamaha's parts total was slightly higher than the Honda's; and with the extra bucks you would spend obtaining a YFZ (MSRP advantage of $400, but word on the street is it's even more than that thanks to discounts available on the Honda), its total cost in our Stage 2 project far exceeded that of the Honda. However, while Campbell spared no expense in the components he chose for his machine, the mods he made were far less intrusive and labor-intensive.

In order to make the Yamaha moto-ready, we decided to follow the de rigueur racing mods. Up front, the stock A-arms were tossed in favor of Walsh Race Craft +3 units. The wider stance is a favorite among moto racers, allowing them to corner faster with less front-end roll. The Walsh Race Craft arms can also be adjusted to a +1 forward stance, increasing the wheelbase and changing the fore/aft weight distribution of the machine. Elka's compression-adjustable reservoir shocks were fitted to handle the increased wheel travel; and their racing damping and adjustability will offer us the opportunity to try and tune the suspension to suit any surface on which we're racing. WER's compact steering damper was fitted between the front frame tubes, well out of harm's way (see review in the Nov. '04 issue). The WER unit helps eliminate headshake on braking bumps and other irregularities. In the rear, a Team Industries 2+2 axle completed our wide-wheelbase conversion. Maxxis Razr MX tires and burly Douglas wheels would fight for traction and resist the pounding from jumped doubles and triples. Most racing organizations require nerf bars to keep machines from getting tangled, so on went a set of X-Factor nerf bars and a pair of larger footpegs with more-aggressively cut teeth for better grip while wrestling the YFZ. A set of Zing CT Racing graphics gave our machine a real race-inspired faade. Since the Yamaha already had a motor advantage over the Honda, only the most moderate of changes were planned. A CT Racing full exhaust system replaced our GYT-R slip-on muffler, and the airbox lid was thrown onto the scrap heap to allow the large air filter to breathe without restricting the incoming flow. The only internal mod the YFZ received in this round was a Hinson billet clutch basket, installed to withstand the abuses of hard starts and aggressive riding.

The Honda, on the other hand, had some catching up to do. However, the more you change, the more likely you are to get it wrong the first time, so our 450R has been through a host of changes even on its way to Stage 2. In the interests of balanced competition, the Honda received a list of modifications similar to the YFZ's. Up front, the Goldenwest crew assembled a well-thought-out plan of attack to transform the Honda into a contender. A Houser long-travel front-end kit brought the ride height down and bore the wide stance common at tracks. Fitted with a set of Elka adjustable shocks, Douglas wheels and grippy ITP MXR4 tires, the Honda began to look less like the frumpy stocker it was. Out back, a Houser +1 swingarm, linkage and another Elka shock were installed to increase the wheelbase and add some much-needed rear-wheel travel to act in a composed manner on the rough tracks of Southern California. With the suspension looking to be on par with the competition, it was now time to try to address the biggest discrepancy between the two machines: power. While the smooth and friendly power delivery of the Honda is a favorite of trail riders, it just doesn't cut it on the track, especially when you are begging for that last 1000 rpm to urge you over the double or triple you've just committed to clearing. Delving inside the motor, Goldenwest removed the stock camshaft and installed a more-aggressively ground HRC kit camshaft to give the motor more power overall and a higher-revving top-end hit. HRC's kit for the TRX also comes with an airbox top and muffler insert. We kept the airbox top, as it allowed nearly unrestricted access to the filter while trying to divert dirt away from the intake. As well as the stock muffler and kit insert worked, we wanted more, so we installed a Big Gun full system to give the TRX some more bite to match its racy visual bark after Goldenwest changed the complete set of plastics and graphics to its new Elsinore-inspired kit.

Dubbed the Pimp Wagon, the Honda was nevertheless decked out in "smart money" components that did the job well enough without breaking the bank.

Hitting the track
Back-to-back comparisons with our two fast guys are something we need to work on, as they're throttle-incompatible: Campbell is strictly a thumb guy, while Finley can't operate without a twist. Our more-pedestrian riders were able to switch back and forth (the rest of us are less finicky about throttle style).

The Yamaha's edge is now just that--a bit of an advantage. Watching our old (yeah right, 32 and 35 years old ... ) pros out on the track, on a given day it looked as if either one could be faster. On the first day of testing, the shocks on the Honda were really far off, but the power through the Big Gun Race Series exhaust was spot-on; it gave a good burst, as the YFZ does. In fact, with the stickier tires, the Honda would really explode out of corners.

On our second testing day, we had the Honda's shocks sorted a bit more; but then we swapped to a Duncan Racing Fat Boy 4 system, which returned its laid-back power delivery, and the quad worked far less well on the track. We'll be putting the Big Gun back on soon.

The Yamaha's Elkas aren't a much better setup right now either, but the quad will pound the rough stuff without bottoming much. In fact, Campbell has used it a few times in several local races with some success (a win and a couple of podiums; plus, he had one sure win slip away due to a lack of preparation--see page 70). Our immediate concern with the Yamaha is a distinct lack of traction out back. This is probably due to the low ride-height setup, but we're also going to try some pressure changes on the Maxxis Razr MXs to see if we can coax more traction from the rear rubber.

The Next Steps
It's obvious on both quads that we could get quite a bit more from the suspension. In order to avoid chasing our tails and pursuing half-baked theories, we'll be doing a session or two with the technicians from Elka to get both machines fully dialed in.

Next up for the Yamaha, we're going to address everyone's number-one complaint: the stiff thumb throttle. Yes, it's a small detail, but it's a serious distraction for a lot of our riders to get into a groove after three or four laps only to have their thumb start to burn.

We're still planning on doing some more motor work on each of the machines so we can really put the spurs to them, but first we have to sort them out so we can get the most from them as they are.