CR250AF-1

WE RIDE SERVICE HONDA’S CR250AF TWO-STROKE MOTOCROSS BIKE

March 12, 2014
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Aside from the sampling of aftermarket goodies, the Service Honda has the fit and finish of an OEM bike. It utilizes almost all stock parts and even the stock 2001 pipe will fit.

 

When four-strokes motocross bikes took over the motocross world—the second time, not the first time—only Yamaha and the European brands stayed in the two-stroke business. And that was a shame. Imagine what would have happened if Honda, Kawasaki, and Suzuki continued to offer and develop two-strokes for motocross. Even if they couldn’t justify all-new designs, they could have easily put the old two-stroke engines in their modern four-stroke running gear. It is not a stretch to see that Kawasaki could have used the KX250F four-stroke chassis to build a modern KX250 two-stroke. Suzuki could have done the same with an RM-Z250/RM250 hybrid. And, of course, Honda could have produced a CRF250/CR250 blend. But, they didn’t.

It could be said that the two-stroke philosophies of Honda, Suzuki, Kawasaki and, to a lesser extent, Yamaha handed the two-stroke market over to KTM—and KTM made hay with it, using their line of 125, 150, 200, 250 and 300cc two-strokes to build a lucrative business niche.

SINCE 1997, SERVICE HONDA HAS EXPANDED ITS LINE WITH THE KX250AF, KX500AF, CR125AF, CR250AF, CR500AF AND THE JUNIOR 250R, WHICH IS A CRF250X ENGINE IN A CRF150 CHASSIS.

The indifferent Japanese manufacturers didn’t have to blaze a new trail on their way to two-stroke success; all they had to do was follow in the footsteps of Service Honda. Service Honda’s number one goal is to produce a unique line of bikes that the public wants but can’t get from the “Big Four.” What Honda, Kawasaki, Suzuki and Yamaha refuse to do, Service Honda does with a smile.

A.J. Waggoner built his first Honda CR500AF (AF stands for “aluminum frame”) for personal use in 1997. The 500cc two-stroke engine was the perfect candidate for four reasons:

    (1)
The large displacement two-stroke engine will always be fast, no matter how far four-stoke technology has developed.

 

(2)
The 500s produce a unique type of power that makes for a completely different riding experience.

    (3)
500s were never produced in aluminum frames, so they started looking antiquated back in 1997 when the Honda CR250 sported the first Delta-Box aluminum frame.

    (4)
There is still a big cult following of folks who missed 500s. Once people saw what A.J. had built for himself, A.J.’s custom motorcycle business caught fire.

Service Honda chose the 2001 engine over the newer case reed engines for breadth of power and simplicity.

Since 1997, Service Honda has expanded its line with the KX250AF, KX500AF, CR125AF, CR250AF, CR500AF and the Junior 250R, which is a CRF250X engine in a CRF150 chassis. At first glance, a modern CR250 may not have as much charm as a CR500, as it already had an aluminum frame and stayed in production until 2007. If, however, you saw the old Honda CR250 sitting next to Service Honda’s CR250AF, there would be no question of appeal. MXA has tested Service Honda’s flagship CR500AF and their KX500AF. We were impressed with both, but we wanted to experience something new—something we could keep on the pipe for more than a split second. Let’s face it, 500s are super fun and super fast, but they are hard to ride. Knowing what Service Honda could do, we thought that the CR250AF could be their best race weapon yet.

Each Service Honda bike is built to order from the ground up. Since the bike is already in pieces when the customer places his order, Service Honda can build the bike up with all the aftermarket bling the consumer wants to order. This stage of the process is the prime time to powder-coat the frame or add special goodies and other touches. Replica bikes are popular, and Service Honda has done many David Bailey and Jeremy McGrath replicas with retro graphics and red or white powder-coated frames. A CR250AF costs close to $12,000.

IT WOULD BE LOGICAL TO ASSUME THAT THEY WOULD USE THE MOST MODERN ENGINE. BUT, MOST DEVOUT CR250 AFICIONADOS DON’T BELIEVE THAT HONDA GOT THE BUGS WORKED OUT OF THEIR QUIRKY 2007 ENGINE.

The CRF250 chassis meant CRF250 spec suspension. The 250 two-stroke isn’t heavier, but it overpowered the suspenders.

Service Honda’s first step was to choose the engine. The 2007 model was the final CR250 two-stroke engine produced by Honda. It would be logical to assume that they would use the most modern engine, but most devout CR250 aficionados don’t believe that Honda got the bugs worked out of their quirky, albeit high tech, case reed, RC, electronic power valve-equipped 2007 engine. When Service Honda compared the 2001 engine to the updated case-reed engine, they found that peak horsepower was about the same, but the 2001 had a much broader, more usable powerband on the track. The less-complex, faster engine was the obvious pick.

The next step was fitting the engine into a 2012 CRF250 chassis. For the most part, the location of the engine is limited by the location of the countershaft sprocket. Service Honda discovered some leeway in tilting the engine forward or backward. In testing their prototype, Service Honda tried to optimize this spec. They went up 3mm from their original position, moving the weight bias slightly rearward.

Honda continues to produce all the necessary parts (and you can order all the parts through your local Honda dealer) to rebuild a 2001 CR250 engine; however, Service Honda did a little mixing and matching to get the optimum setup. The 2000 CR250 came with a 38mm Keihin carburetor, but for 2001, Honda spec’ed a Mikuni carb. Service Honda felt that the Mikuni was a good piece of equipment, but that it was difficult to keep jetted properly in varying conditions. So, they decided to use the 2000 carburetor with the 2001 engine, which had a couple updates from the previous year—new cylinder port shapes and timing and a new reed-pedal-stopper shape.

The four-stroke airbox wasn’t even close to mating with the two-stroke engine, in part because the intake on the two-stroke is much lower. Service Honda’s solution was to use a combination of two-stroke intake parts, some modified parts and a number of custom-built parts made in their in-house machine shop.

A 2000-spec Keihin carb was chosen over the 2001-spec Mikuni for better performance in varying conditions.

Service Honda went the extra mile to make sure customers could use any aftermarket pipe designed for a 2001 CR250. When a customer submits his order, he can choose between FMF and Pro Circuit pipes, and each brand has several options in its line. Our test bike was equipped with a Pro Circuit Platinum pipe and R-304 silencer. As a final touch, Service Honda installed aftermarket blue radiator hoses, a red-anodized billet rear-brake guard, master-cylinder cover, wheel spacers, brake clevis, and a Fasst Company brake-return spring.

EVERY TWO-STROKE HAS ITS OWN PERSONALITY. SOME OF THEM HIT HARD WITH INSTANTANEOUS, WHEEL-SPINNING BARK, AND SOME EASE INTO THEIR SWEET SPOT WITH A CONTROLLED SURGE.

Every two-stroke has its own personality. Some of them hit hard with instantaneous, wheel-spinning bark, and some ease into their sweet spot with a controlled surge. When the CR250AF came into the midrange, there was a slight warning, and then things happened in a hurry. The power snapped to attention, but not in a way that wanted to spin the rear wheel. Instead, the power surge came on just smooth enough to hook up and push the rider back on the seat. The CR250AF wasn’t a top-end screecher, but it didn’t have to be short-shifted, either. Test riders had no trouble keeping the rpm in the mid-to-top before it signed off. In a gun-and-run face-off with a new YZ250, the CR250AF walks away. Chasing after KTM 250SX riders, the Honda held its own.

Customers get their choice of FMF or Pro Circuit exhaust systems. Our bike had a Pro Circuit pipe and silencer.

There were two things hampering the power of MXA’s Service Honda CR250AF. The biggest problem was getting the power to the ground. The 100/90 rear tire that came on the CRF250 chassis was too small. Off a cement starting pad, the rear wheel of our CR250AF test bike lit up like a Christmas tree. The 100 rear is really a 125 tire at heart. Dunlop recommends a 110/80 for most 250F riders and a 110/90 for 250 two-strokes, so the 100 is actually two sizes too small.

The second problem was a slight hesitation down low in the powerband. The bike was jetted for a cold day in Indiana, and that didn’t work so well in SoCal. When the engine got hot, it ran better, but it would take a rear tire and a jetting change to get the best use of the bike’s power.

EVERY MXA TEST RIDER WAS IMMEDIATELY COMFORTABLE WITH THE HANDLING OF THE CR250AF. IN TRUTH, THE CURRENT HONDA CRF250 CHASSIS IS BETTER SUITED TO THE TWO-STROKE ENGINE THAN THE FOUR-STROKE.

The MXA test riders thought that customers would line up to buy a modern CR250 two-stroke.

Every MXA test rider was immediately comfortable with the handling of the CR250AF. In truth, the current Honda CRF250 chassis is better suited to the two-stroke engine than the four–stroke. Four-stokes tend to ride front-end heavy, and that can exaggerate the oversteering tendency and forward bias of the CRF250 frame. The lightweight and snappy power of the CR250 engine allowed the front end to float, which mitigated the negative handling tendencies. Through turns, the CR250AF rewarded an aggressive right wrist and made test riders want to attack berms. It carved tight lines, changed direction on a whim and wheelied over obstacles at a moment’s notice.

The only hindrance to handling was the soft suspension. The claimed curb weight of the CRF250 four-stroke is 222 pounds, while the CR250 two-stroke is 216 pounds. If it’s 6 pounds lighter, why is the suspension too soft? Extra horsepower (and the CR250 two-stroke makes 47 horsepower compared to the 35 of the CRF250 four-stroke) puts a big demand on a bike; when the 250 accelerates over bumps, the shock goes through its stroke quickly. We cranked in the compression on the forks and shock, adding both high- and low-speed damping to get by. Only featherweight riders could be happy with the spring rates.

 

The 2012 Honda CRF frame actually handled better with the two-stroke engine nestled in its cradle than the standard-issue four-stroke.

Although the fork springs, shock spring and rear tire were a bad spec for this bike, the chassis worked very well with the two-stroke powerband—better than it does with the four-stroke engine. Every tester reported that the bike performed magnificently, with all the best traits that two-stroke aficionados praise. Service Honda made a smart decision going with the 2001 engine.

The CR250AF isn’t some modern/retro trophy; it’s a worthy race bike built with readily available parts. At $11,999, it will require that a prospective buyer be ready to take a big bite out of his billfold, but considering that Service Honda has to order all the engine parts individually and start assembly from scratch, the price is justified.

This is one bike that is built from two–and the extra cost comes from the custom build process. It’s ironic that the best feature of this custom bike is that it has the finish and look of an OEM machine. The sad part is that this OEM CR250 two-stroke could be made by the factory for chicken feed—since they have all the parts in stock.

SEE MXA’S CR250AF VIDEO HERE

 

For more information, go to
www.servicehonda.com.

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