This feature was first published in ADB issue #463 – April 2018.
Words: Mitch Lees
Photos: Olly Malone
Until KTM got serious about its enduro bikes nearly a decade ago, off-road racers were forced to pilot motocrossers in the bush if they wanted any chance of being competitive. Trail or enduro bikes were too heavy, too softly sprung and often lacked power for hard-core fast-paced bush racing.
Take the Honda XR or early model WR-F for example: Sure they were raced in enduro and won championships with the right pilot behind the ’bar, but the CR and YZ motocross range were faster and more competitive in off-road disciplines like grasstrack.
So Yamaha went about creating a bike that was purpose built for off-road racing, to fill the void between its WR450F and YZ450F, and called it the YZ450FX. It sports the same rearward-slanted cylinder design found in the WR450F and YZ450F, carries the same bilateral beam frame and KYB twin-chamber suspension found on the YZ-F and WR-F, but has a host of bush-specific racing accessories that make it one of the best grasstrack racers.
It’s pretty much a YZ-F with softer suspension, more flywheel weight, bush-specific clutch components, an 18-inch rear wheel and none of the ADR gear that comes with the WR450F, including the choked up exhaust and fat headlight. This slightly firmer, more aggressive and lighter version of the WR450F is the ultimate grasstrack racing machine.
If getting tonnes of fully-sick air plays no part in your racing, and off-camber, smooth corners are your road map, then the YZ450FX will be hard to beat.
THE PUNCH
Like a stoner after punching five bongs and a hash cookie, the YZ450FX is hungry. It wants to eat, so let it. The power it produces is far stronger and more aggressive than the WR450F, making it superior in sprint, cross-country and, of course, grasstrack disciplines.
Yamaha has achieved this by bolting on the YZ450F exhaust, which is shorter and breathes better than the WR450F, and hotting up the ECU. Without the threat of collarbone-shattering trees within a bee’s dick of your handlebar, it’s possible to get a little wilder on the YZ450FX than the WR450F, and why wouldn’t you?
The WR450F is noticeably slower than the YZ450FX, especially if you make a small error and step out of line because you were feeding the horse too many carrots. In the trees this could spell disaster on the YZ450FX but on a grasstrack, if you open the throttle too hard and too early just hold on as it drifts wide and powers out! The YZ-FX lives to dig trenches and get sideways on beautifully manicured, country-club lawn. Just try it, we dare you!
The YZ450FX has been mapped for racing, not trail conditions like the WR450F. If you’re hoping to plod through the trees on this bike, you’re in for a fist fight, but if you’ve bought it to race the local grasstrack series or cross-country event, then you’re in luck. Just off idle it bogs and spits a little more than the WR450F, but when racing grasstrack you’re never just off idle and the middle part of the rev range is where the YZ450FX makes most of its power.
The YZ450FX sounds better than the WR450F and pulls like a tractor in deep sand or when clicking gears down a long straight. Despite the livelier engine, it still finds excellent traction and, as Yamaha has established with this engine across all its models, the rearward-slanted donk allows the rider to carry taller gears through corners on other bikes, and still exit with the same gusto they would if they were a gear lower on another bike.
THE BOINGERS
The suspension on the YZ450F is designed to be jumped and cased. It’s slightly firmer, making it great for beat-up motocross tracks and hucking big triples. But when negotiating small bumps on a grasstrack the YZ450F can step out and become a little skatey as the suspension needs more force to move. The WR-F is too soft to be raced in standard trim. Like all WRs, it’s built for sitting back and watching Home and Away with beer in hand, not ’bar bashing around a fast, rough grasstrack.
The YZ-FX is the perfect blend of the two. It won’t blow through the suspension stroke on the entrance to rough corners, instead it holds up and skips across the top of regulation-size grasstrack braking bumps. It also won’t bash your forearms to a pulp if the track is gnarly. It’s the perfect middle ground for bumps found on a grasstrack, absorbing everything with ease but remaining stiff enough to prevent the dreaded rear-end squat under hard acceleration. It will handle long ski jumps often found on natural-terrain grasstrack, providing the landing isn’t too harsh, and will eat up square-edged bumps with a firm shock action.
While the engine is aggressive enough to race, but won’t rip your arms out of their sockets, and the suspension glides over medium-sized bumps, the real benefit of this bike when racing in the bush is the chassis and ergos. It’s designed to be fast and accurate, just like a race bike should be.
It’s more compact in the cockpit than the WR-F, giving the illusion of better handling, and the rear-end doesn’t have any of the clutter associated with an ADR-compliant bike. It’s fast, accurate and nimble.
It’s not as soft as the WR450F and, more importantly, it’s lighter, which means you can push harder and longer through small braking bumps on a grasstrack and tip it into turns harder. But it’s not as stiff as a YZ450F so it won’t rattle your teeth out after a 10-minute grasstrack session.
The engine is still incredibly strong and will pull almost fourth out of tight corners but it won’t whisky throttle you into spectators. Its greatest asset compared with the WR450F’s power is the mid-range surge. Unlike the WR-F, where the power tapers off to prevent collisions with trees, the YZ-FX power just keeps hitting, but not as abruptly as the YZ-F.
VERDICT
The YZ450FX is what I would like in the WR450F. A little more mid-range punch and a nimbler, better-suspended chassis that feels lighter and more agile in the bush. I understand Yamaha is limited by ADR-compliance requirements but a more compact cockpit on the WR-F, like the YZ-FX, would make the bike feel more streamlined and agile.
The YZ450FX makes for the ultimate grasstrack machine. It would be great in the trees as well, but the power the Yamaha engine produces lends itself to more open terrain. The engine wants to be revved and doesn’t like slow speed chopping and changing so grass-track hauling is the ultimate YZ450FX playground.
