MXA BUILDS THE YAMAHA YZ250F OF YOUR DREAMS

September 9, 2014
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YZ250F_INTRO

Easily one of the most intriguing bikes to come out of the factories in 2014, the Yamaha YZ250F is a monumental step forward in the evolution of the YZ250F. The first modern-day 250 four-stroke, the 2001 Yamaha YZ250F, was an engineering marvel. It revolutionized a class previously owned by 125cc two-strokes. Yamaha is one of the main reasons four-strokes now hold court in motocross (of course, the AMA’s generous size displacement for four-strokes was the nail in the two-stroke coffin).

yellberm750

Our dream of building a retro YZ250F wouldn’t have been possible without the help of great aftermarket companies. The list includes Works Connection (engine plugs, skid plate, axle blocks, Peg Armor), Ride Engineering (lowering link and triple clamps), Cycra Racing (retro yellow plastics), Factory Effex (custom graphics and seat cover), Renthal (Fatbars, sprockets, Kevlar grips and chain), DR.D (NS-4 exhaust, lowering kit and hour meter), Twin Air (Powerflow kit and air filter), Dubya (wheelset), Graeme Brough (suspension), and Hinson (slipper clutch and X-Trig preload adjuster).

In hindsight, Yamaha hit a home run with the YZ250F. How different the market would be in 2014 if the 2001 YZ250F hadn’t been accepted by the consumer or if the bike had suffered from mechanical issues. Instead, the YZ250F was ironclad tough and considerably easier to ride than any 125 two-stroke. Other manufacturers followed the four-stroke path several years later—building on the groundwork that Yamaha had laid. So while many early 250 four-strokes had teething issues, Yamaha proved that they could be reliable.

YZ250F_HUBS

We couldn’t live with ourselves if we built a retro-themed YZ250F and ignored the stock silver wheels. Much like the works Yamahas of the late 1970s, we laced up gold rims, silver spokes and black hubs. Dubya answered the call with D.I.D DirtStar rims and Talon carbon fiber hubs. Not only did the wheels tie the aesthetics of our bike together, but the high-quality components added durability.

For many years, the MXA wrecking crew was puzzled by Yamaha’s lackadaisical approach to updating the YZ250F. The blue crew had been ahead of the four-stroke curve for so long, but they chose to rest on their laurels, and that allowed the competition to catch up. In short order, other 250 four-strokes surpassed the YZ250F in terms of performance and technological advancement.

YZ250F_FORKS

The industry is replete with suspension tuners. We had our pick of the litter and decided to go with Graeme Brough. It was an easy call. Brough has an impressive resume and has worked at the factory level. Graeme took the already-great Kayaba SSS suspension and made it better. He dropped the stiff springs for a lighter rate and tweaked the valving for maximum plushness.

It originally appeared that Yamaha would swing for the fences in 2010. They revised their perimeter aluminum frame to straighten the intake tract (a must-do for electronic fuel injection). They pumped up the engine and designed a flat-bottom fuel tank, which made installing a fuel pump easier. They wisely kept the proven Kayaba SSS suspension. Sadly for the times, the 2010 YZ250F came with a Keihin carburetor (an unpopular move in the court of public opinion), and the engine wasn’t massively improved. It was just more of the same for the 2010 YZ250F.

YZ250F_CLUTCH

One of the most interesting parts on our retro YZ250F was the Hinson slipper clutch. We’ve noticed that the YZ250F suffers from heavy engine braking when letting off the throttle and downshifting. The load causes the suspension to kick and become unpredictable. That was no longer the case after we added the Hinson slipper clutch.

The MXA wrecking crew finally got its wish in 2014. Yamaha stepped up to the plate and delivered an all-new YZ250F with all the technological advancements mated to the already proven equipment. If you’ve read our 250 shootout, then you’re aware of our glowing approval of the direction that Yamaha took. It was barely edged out by the Kawasaki KX250F. Why? The powerband isn’t quite as sweet as the KX250F’s, plain and simple.

YZ250F_BRAKE

We’ve had great luck with the Moto-Master oversized rotor. The bracket goes on easily, while the rotor provides excellent braking power. We opted for the stock brake pads, as we do with any aftermarket rotor. Stock pads tend to give the best feel and feedback at the lever.

The MXA wrecking crew embarked on a journey to build a 2014 Yamaha YZ250F that would top the 250 class—and do so with force. Of course, we couldn’t help but pay homage to Yamaha’s illustrious history. Cycra Racing dialed us in with a complete set of retro butterscotch-yellow plastics. Dubya provided gold wheels (just like works Yamaha bikes of the late 1970s), silver spokes and black carbon fiber hubs. Details, such as engine plugs and axle blocks, were handled by Works Connection. We buttoned up the aesthetics with custom Factory Effex graphics and a seat cover.

YZ250F_ACTION_1

In stock trim, the 2014 YZ250F can cut tight lines, though the front end sometimes suffers from an unwelcome wiggle at turn-in. The DR.D lowering kit, combined with the Hinson slipper clutch and plush suspension, eradicated that sensation. Understand that the MXA wrecking crew didn’t touch the YZ250F engine. Instead, we focused on performance bolt-on products that would make a stout engine better.

Though our YZ250F project bike harks back to the glory days of Yamaha, there’s more than meets the eye. Underneath the plastics kit is a Hinson slipper clutch, Twin Air Powerflow air filter kit, and a DR.D exhaust system. We figured that Doug Dubach, chief test rider at Yamaha, would know what the YZ250F needed to bolster performance.

YZ250F_SHOCK

Graeme Brough ditched the stock 5.6 N/mm shock spring for a lighter 5.4 N/mm spring. He matched the fork adjustments in order to balance the chassis. Graeme also installed an X-Trig preload adjuster to make sag changes with ease. And, because we were so particular about having the YZ250F look sharp, we kindly asked that Brough install a black spring instead of the standard blue. It’s the little things that matter.

Since 2006, we’ve gushed about Kayaba’s SSS suspension. Having said that, we shipped out our YZ250F forks and shock to Graeme Brough. It sounds preposterous to mess with success, but Yamaha beefed up the spring rates for 2014, making them too stiff for light riders (they have fixed this error for 2015). We had Graeme swap the springs and change the valving specifically for our smaller testers. Given Brough’s excellent track record, we knew he was the guy to improve on the already superb suspension.

YZ250F_RADIATOR

DR.D has been selling a YZ250F radiator lowering kit for years. The brackets lower the radiators by 24mm. In turn, the lower center of gravity improves handling. Easy to install and effective at making our YZ250F project bike more nimble in corners, the DR.D radiator lowering kit is a smart buy.

YZ250F_MUFFLER

Doug Dubach, of DR.D, doesn’t build exhaust systems on a dynamometer. Instead, he builds prototype pipes and puts them in real-world situations—at the track. For this reason, DR.D has a reputation for making excellent exhausts. Dubach’s NS-4 added midrange and top-end power, but it did take away some of the bottom-end grunt that the YZ250F is known for.

What was the total cost of our bike build? Since our plan was to build the ultimate YZ250F, the MXA wrecking crew doesn’t worry about money. We want to show what is possible and you don’t have to do everything we did —but we want you to see all of the option. That said, we spent several thousand dollars, but it was worth every penny. Not only did we vastly improve the YZ250F powerband without sacrificing durability, but we also fixed flaws in other areas. An oversized Moto-Master front brake stopped us in our tracks. A Ride Engineering longer link arm helped balance the suspension and keep the shock from blowing through the initial part of the stroke. Then there were the sweet Cycra plastics and accompanying anodized parts that were attractive and sharp-looking.

YZ250F_LINK

In conjunction with Graeme Brough’s suspension mods, we opted for a Ride Engineering lowering link. The pull rod is longer than stock and drops the rear end of the bike. As a result, the initial part of the shock’s stroke is stiffened for better balance front to rear.

YZ250F_ACTION 3

We love the power and layout of the 2014-15 Yamaha YZ250F. We could live happily ever after with the stocker, but what fun would that be?

 

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