Bike Dissected: Merriman’s 2013 Yamaha WR450F

In their first season in off-road, CDR Yamaha has turned the best-selling WR450F into a potent weapon for former four-time world champion, Stefan Merriman. This article originally appeared in Transmoto Dirt Bike Magazine‘s 2013 November (#37) Issue. 

It’s been a while since Craig Dack has been described as a newcomer, but the start of the 2013 off-road season saw him and his CDR Yamaha Off-Road team as just that. Taking over the enduro reins from the successful Ballard’s team meant the stakes were high for one of the most recognisable race teams Australia has ever seen. With numerous MX and SX titles under Dack’s belt, headlights and hardwoods were a whole new hunting ground for the four-time Mister Motocross winner. Success would further build CDR’s reputation as pretty much unbeatable. Failure, it seems, was never discussed.

As the team’s experience in motocross shows, having the right mix of riders is the key to a successful championship tilt. While Daniel Milner (2013 A4DE and AORC champion) provides the youth, the experience of four-time EWC champ, Stefan Merriman, has helped mould the team into consistent frontrunners.

With the change of team owners came a box-fresh production WR450F. Dack enlisted the set-up talents of the recently retired motocross legend, Josh Coppins, for the initial shakedown tests; which was essential as the project had started later than planned. The first time that Stefan threw a leg over the bike was early January of this year, though the WR-F isn’t exactly new territory for the New Zealand-born star. Nor is its engine new to the team, as CDR worked on this five-valve unit for years until Yamaha’s YZ450F changed to the four-valve, reverse engine layout for 2010.

With plenty of previous data to work from – albeit from an MX perspective – how did CDR mould Merriman’s WR450F into an AORC frontrunner?

Engine

“There’s only so much I want tell you about this,” says Dack cagily. “Okay, let’s start with what you won’t tell us then,” we replied. Dack is the first to acknowledge that the MX-experienced team initially went too far with the power hit and had to tame it down, especially for Merriman, who likes a very smooth, tractable power delivery. CDR-designed cams were made in New Zealand, but all the other work is performed in-house. The head gets flowed to smooth out the power, while a GYTR clutch basket gets the nod for durability and feel.

Fuel Tank

The fuel tank is one of the more obvious changes on the bike. It’s the same YZ250F carbon fibre Rinaldi unit that’s used in the MX GPs. It offers a litre extra capacity over standard and fits the WR-F perfectly, as its frame dimensions are now the same as the YZ250’s. It’s essential for the cross-country events, where the bikes run for three hours straight. With this tank, Merriman can run for more than an hour-and-a-half without the CDR guys having to tune the bike for fuel conservation. A single fuel stop means they have the same pitstop strategy as their KTM rivals.

Ignition & Mapping

A programmable Vortex ECU unit replaces the standard and can be adjusted by either plugging a lappy into the unit that is relocated to inside the airbox, or via the bar-mounted switch. There are 10 settings for different power curves and the same number of options for the air/fuel mixture. The bar switch allows the preferred race map to be set and then instantly replaced by a second setting, used when conditions get wet or muddy. For events held entirely in these trickier conditions, a heavier flywheel weight is used to help the rear Dunlop find traction.

Subframe

Merriman is not the tallest guy to ever swing a leg over a bike, so CDR has ensured that this WR450F is tailored to his size. The standard subframe is replaced by a bolt-on YZ250F unit and that moves it down 20mm in the seating area. This mod necessitates the use of YZ sideplates, although the exhaust mount remains the same. A One Industries gripper seat cover keeps the actual saddle at the production height and a 20mm ‘bump’ helps Stefan brace against the 450’s acceleration. This saddle is alternated for just a plain gripper seat when conditions dictate.

Cockpit

Like their MX brothers, CDR’s enduro bikes run the standard triple clamps. Having tested many of the aftermarket products out there, the team riders prefer the feel the production clamps offer. So that naturally means that the bike runs the standard offset and rake and trail. Renthal bars wear the stock brake and clutch levers, likewise the headlight plastic and both fenders. Looking over the bars, the bike runs Dunlop tyres on its standard wheel assemblies. CDR swaps between Soft, Intermediate and Hard options, depending on the track and conditions.

Brakes

It’s easier to list what’s not been changed here. Lever, perch, pedal, master cylinders, rear line and front disc are all as standard as they come. At the front, only the line changes; the standard replaced by a Goodridge Kevlar item, whereas the back only has the disc changed. This is to a thicker, solid disc, which is normally used as a wet weather option. Merriman likes to run this disc come rain or shine, claiming that it offers more feel and remains clog-free. The team tried an oversize front disc, but it was too fierce for Merriman’s braking style.

Suspension

According to Dack, the biggest slice of the development pie goes on the bike’s suspension. The race WR-F runs YZ450F front forks with internal valving and spring mods to suit Merriman’s weight and riding style. This also helps streamline the whole development process as data can be shared from the MX machines. The rear shock is standard-issue WR450F, again revalved and re-sprung to suit Merriman’s preferences. If the bike changes from round to round, it’s largely the fettling of these suspension components that are the likely recipients of the time spent.

Testing

From that three-day Coppins test, to Merriman competing in the AORC, the CDR Yamaha WR450F has seen a season-long development cycle. And even with the 2013 title run and won, there’s no letting up with that testing schedule. Recently, technicians from Yamaha’s Japanese HQ have been out to Australia to test with CDR. It’s rumoured that season 2014 will see the same model of WR-F being campaigned, with an all-new reverse-cylinder enduro bike due in 2015. With the factory actively taking feedback from testing on Australian soil, expect the production version of the next-generation WR450F to handle the rocky terrain and fine dust of our country even better.

Independent View

As you’d expect, manufacturers are always prone to say that their race bikes are very similar to the production machines in order to keep sales going strong. But they don’t always shoot 100% straight about details of their race bikes’ make-up. Some of Dack’s “I can’t tell you that” details are fairly easy to decipher if you stand there looking at Merriman’s bike long enough – especially when you have a standard YZ-F and WR-F to compare it with. Even to the untrained eye, it’s obvious that Merriman’s swingarm is straight off a YZ450F (because it uses a different shape near its pivot and no telltale plastic bung on the side of it, like the WR450F’s). We reckon that’s the MX bike’s linkage under there, too. The same goes for the triple clamps. The jury’s out on the radiators, but we wouldn’t be surprised if they were originally designed for life on the other side of the tracks, too. But whichever way you dissect the #24 bike and CDR’s first season in enduro circles, the results are impressive. With the YZ250F of Daniel Milner snaring the Outright win in both the A4DE and AORC (the first 250cc four-stroke ever to do so) and Stefan Merriman having a strong second half of the season to charge home fourth Outright, expect the blue team to be even stronger in 2014.

Stefan Merriman – E2 Rider

This is my second year on Yamaha’s WR450F, the first being for the Ballard’s Offroad team last season. Even though CDR and I started with a stock bike this year and initially went in a different direction to what I had in previous years, my race bike is now pretty similar to last year’s one. That said, the suspension is quite a bit different, and working with the CDR team’s suspension technician, Gary Benn, has been really good for sorting that. I’m pretty particular with suspension set-up these days. After a bit of a slow start to the season, I finished second in the E2 class this year, and only five points off third in the Outright standings. I was happy with that because I’m now 40, and it does get harder to keep up with the younger guys. The best thing about being older – or more experienced, as I like to say – is that you don’t get hung up on just one aspect of the bike or race. I now take a wider view than when I was greener and maybe keener. I’ll use two race bikes per year and a further three for training purposes. Outside racing, I’ll ride two-to-three days a week, and will mix it up with cross-training to keep myself motivated. Hopefully, I’ll stay blue for season 2014.”

Craig Dack – Team Manager

Stefan is very precise with his bike set-up and it’s our job to accommodate him and build a bike that he’s comfortable on. He’s the opposite of an MX racer – he likes the power smooth, soft and flowing. Likewise with his brakes. The WR450F is Australia’s best-selling dirt bike because it fits riders of all abilities. That means that we have to modify it for elite-level racers. The bike’s standout aspect is its bulletproof engine, and this year’s A4DE offered further proof of that. When Stefan hit a tree stump during the race, he holed the engine case and punctured the radiator. He still had six minutes of competition left, before a 20-minute transport stage back to the pits, but he didn’t back off. At the stop, we simply replaced the case and radiator, refilled the bike with oil and coolant, before racing the remaining two days of the event. The engine was fine. The whole CDR team absolutely loves being involved in the AORC. There’s a friendly atmosphere in the pits, but there’s no mistaking the dedication of these guys once they put their helmets on. And they’re tough. Milner and Merriman have both finished races with no skin on their palms, and then backed it up the next day. For 2014, I’m hoping we can keep the same riders and team personnel. It’s very satisfying for me to be part of these people’s lives.”

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Want to view this article in magazine form? Grab yourself a print or digital edition of Transmoto Dirt Bike Magazine‘s 2013 November (#37) Issue. CDR Yamaha recently signed Daniel Milner and Chris Hollis for season 2014, and there’s been no official word on where Merriman’s heading.