Bike Dissected: Sheeny’s FMX Machine

7 years ago | Words: Grant O'Brien | Photos: Red Bull Content Pool

Take a look inside the ingeniously modified Honda that 2014 Red Bull X-Fighters champion, Josh Sheehan, triple-flipped into the record books.

COCKPIT

Freestyle motocross riders are very particular about the way they set up the cockpit of their machines. A lot of tricks are executed through or around the bars so confidence in the set-up is important. Josh opts for a higher bend Tag Metals 6091 bar to give him a little more room to get his larger-framed body through with tricks like the Stripper Flip. He uses Tag soft waffle grips, and a set of Klayver custom-made Flip Levers that he then modifies slightly to suit his style. As Ash points out, “Josh doesn’t like the levers too high so he heats up the metal lever with an oxy torch and bends them closer to the bars. They look trick, are very durable, and they are essential for tricks like Super Flips, Indy Flairs, Stripper Flip and Cordova Flip.” To ensure the front-end remains pointing straight ahead while letting go of the bars mid-trick or landing no-handed, Josh uses a GPR4 steering damper that combines with the top triple clamp. “He is pretty picky with how the steering damper feels”, says Ash. “He bleeds it often before each event as the change in temperatures moving from one country to the next causes a little air to build up in them. He also uses a thicker 15 or 20-weight oil so he can increase the resistance if necessary.”    

PERFORMANCE

When Josh trains at his compound in Donnybrook, Western Australia, he tunes his bike to perform his tricks at sea level. Josh has to be so in tune with the performance of his bike’s engine because attempting a trick like the Double Flip with either too little or too much power could mean under- or over-rotating … with dire consequences. In fact, Josh won’t attempt the Double Flip in Mexico City because it’s 2200m above sea level and the engine’s performance suffers massively due to a lack of oxygen. “At higher altitude stops on the tour,” says Josh, “I’ll get Ash to put in a high-comp piston and a different cam to regain some of the lost bottom to mid-range power. But in Mexico, it still doesn’t give me enough power to safely execute the Double.” Ash says they also try different high-octane fuels – and to an extent the fuel-injected CRF450R tunes itself in different altitudes – but they can tweak it either side to improve the power for the conditions. “With the custom aftermarket ignition, we have a bunch of settings with different power curves to choose from to best suit different locations’ temperature and altitude,” says Ash. “It has nine different preset maps, one dial that replicates the pilot jet, mainjet and needle, plus the idle. That lets us run the engine richer or leaner so there’s plenty of adjustment to get it right.”

UNDER THE KNIFE

Core FMX fans will remember the old days where riders hacked away at their two-banger’s plastics and seat to create grab-holes. It wasn’t always pretty, but it did the job. Josh’s CRF450R thumper is a little more complicated as the airbox is closed off for emission control, so he has to spend some time cutting out the guts and top to make room for his grab-holes. He cuts the plastic sideplates enough so he can easily get his hand around the side of the seat, which he only trims slightly because he says it’s just too uncomfortable to ride around with the foam trimmed too lean. “Lucky I’ve got big hands,” says Josh. “I’d rather have the fatter seat for comfort over a thinner one that’s easier to grab.” The pleated seat cover Josh uses is more for looks, and although it offers grip to stop him from sliding backwards, Ash says it’s the grip tape that makes the big difference. “Josh is very picky with hisgrip tape because he can’t afford to slip off the back of the bike halfway through a Double Flip rotation,” Ash points out. “He’ll cover the frame and about a third of the side plastics to ensure his legs have a good area to grip.”

TITANIUM, BABY

Josh is always looking for ways to reduce the weight of his Honda CRF450R because the lighter it is, the easier it is to move around when executing rotating or spin type tricks. Just by removing the stock dual muffler system and replacing it with an FMF titanium header and single Factory 4.1 muffler, the bike dropped two kilos. Josh is more concerned about saving weight than finding more power, and he’s spent some coin this season chasing those savings by replacing most steel bolts with titanium equivalents. That includes the ‘big three’ bolts – wheel axles, swingarm pivot and engine mounts – plus the bolts in the subframe, muffler, seat, plastic, front calliper, triple clamps, clutch and brake perch. The standard footpegs have been replaced with titanium Raptor units, and Josh also has a titanium shock spring that will save another half kilo. It all makes a noticeable difference when he is launching into a 360, Double Flip or Flair.

RUBBER

Josh’s bike gets shipped to each Red Bull X-Fighters event by the organisers and the tyres are supplied to suit the type of dirt the course is built from. “Obviously the tyres don’t make as big of a difference as they do with motocross or supercross,” says Josh. “But sometimes we ride on hardpack courses or, like the recent Athens round, very soft and loamy dirt. So it still helps to have the right tyre for each round of the series to hook up better.” Josh runs 15psi front and rear at most locations and a little higher pressures for really hard surfaces.

GEARED FOR GRUNT

Ash tells us Josh likes to pull away from a standing start in second gear so they replaced the 13/48 standard gearing with a much shorter 13/51 combo for most locations. “This improves bottom-end response,” explains Ash. “The engine also revs out quicker, which means Josh can judge his speed easier heading at the ramp and is less likely to over-jump, thereby making it safer. He can still jump a 110-foot ramp in second, and at courses such as Mexico with high altitude, we’ll go one tooth higher again to compensate for the loss of power.”

HOT, HOT, HOT!

With freestyle motocross, there’s a lot of slow riding and idling, so the engine temperature heats up quickly and runs hot, especially with the four-strokes. The standard radiator cap is rated at a pressure of 1.1 Bar so Josh runs a higher-spec cap with a rating of anywhere between 1.4 and 2 Bar to stop the bike from overheating. According to Ash, “You’ll notice radiator coolant pissing out from a standard bike after idling for a while, so it’s important for us to make sure the CRF450R doesn’t boil while Josh is waiting for his run to begin.”

SUSPENSION

With trick evolution rocketing sky-high over the past decade, riders have really had to be on their game with bike set-up. The G-force in Josh’s Double Flip alone is enough to blow suspension components if they’re built incorrectly and not up to the task. Josh has worked closely with Sydney-based Factory Spec Suspension’s Ken Wheeler to ensure his KYB air forks and Pro Link KYB shock can handle the hardest of hits. “My suspension is not that far off the set-up of a supercross bike with harder compression and slower rebound,” says Josh. “Landing from the Double Flip is by far the harshest impact, so as long as I’m set up correctly for that trick, everything else is fine. I’ve worked with Ken to get a good base setting so the only thing I have to worry about is adjusting my bike’s suspension to suit the climate I’m riding in. When it’s cold, I notice my suspension stiffens, and vice versa in hot temperatures.”

 

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