A day at the flowing layout of Zaca Station MX gave us an eye-opening view into the world of 250F over-bores.
Box stock, Honda’s CRF250R is widely considered the best 250 4-stroke on the planet. Now start bolting on some of the aftermarket performance products which are readily available and your CRF250R can become a fire-breathing, berm-busting monster.
Honda produces perhaps the best 250cc 4-stroke motocross bike on the planet. The CRF250R has been dominating the annual MotoUSA 250F Motocross Shootouts since 2006 with another victory this year completing the three-peat. Finding chinks in the CRF’s red-plated armor is a chore, so we worked with one of the top builders in the industry to find them for us. Our test bike was set up by Jay Clark Enterprises built by the man himself, Jay Clark. The other was a stock CRF250R which allowed for a solid comparison.
The motor ran absolutely perfect and was a highlight for our testers, as was the MB1 suspension which surprised us with its versatility.
The only consistent flaws we’ve found in the rock-solid CRF are minor issues with the carburetion and suspension, and these were two of the primary targets for respected bike builder, Clark, but he didn’t stop there. He’s a totally stand-up guy, but with his particular industry ties there’s plenty of influence for extra motor displacement, so he built us a cheater bike. By the time he finished with our little Honda, the cylinder was overbored 1mm and re-plated to 79mm by Millennium Tech, Parapros Racing custom ported the head, CP Pistons threw in a high-compression 14:1 piston and Hot Cams slipped in their performance camshaft. The extra size bumps the mill to 256cc, and feeding the entire thing is a full-modified race carb from Tokyo Mods while an FMF MegaBomb and Factory 4.1 single muffler handle exhaust on the opposite end.
When it comes to building motors, plenty of guys live by the “go big or go home” mantra – and plenty get to do both when their engine grenades after a few hours. Mr. C certainly likes to hog things out, but he’d rather spend more time at the track enjoying his handiwork than rebuilding it inside his shop in California’s Inland Empire.
“Some bikes can go bigger,” he warns, “but Hondas aren’t good for much more than that.” Hence, the light work by Millennium. He was, however, testing a 269cc YZ-F that same day, so the man certainly likes to go big. The larger bore forces the bike into vet-class or weekend warrior status, and that’s a concern for many racers. Our vet pro tester is entitled to the extra punch, but he felt that the biggest gains are really from the Tokyo Mods race carb.
The Tokyo Mods race
carb was awesome as
was the ignition
switch.
“The extra displacement isn’t really noticeable enough to justify, so I can take it or leave it,” says Tod Sciacqua. “The biggest improvements are from the carb. That motor runs absolutely perfect. There’s no hesitation anywhere through the powerband and it reacts instantly when you twist the throttle. I liked the Tokyo Mods switch for multiple ignition maps also, but mostly left it on the aggressive setting all day once I got a feel for them.”
Our less experienced tester agreed entirely about the carb. When there are gains there are usually tradeoffs. In this case, our ringer found that the stock carburetor is a little better at top-end performance, but both riders clearly preferred the aftermarket set-up. Having a direct link to the rear wheel was also a result of the chassis. The lively motor gives improved response but the MB1-tuned Showa suspension does a magnificent job of converting it to forward drive. The fork and shock were fully revalved with a novice/intermediate in mind. Though fast, at 165 pounds, Sciacqua isn’t huge. Even though he wasn’t the exact target, the MB1 sticks were much better than stock.
Corner speed improved with the stability and balance of the chassis and suspension.
“I loved the suspension,” says “Big Air” Tod. “It’s so stable I can charge through anything without thinking twice. I got used to it and then tried to hit the same section with the stock bike and almost killed myself, it just wouldn’t settle in. Stability and cornering are awesome, and it handled every big jump on the track no problem. I would race on this stuff.”
With Dunlop Geomax tires mounted on TCR wheels, our retro-styled rocket hurtles forward with more authority than any stock 250F. Slowing it down is an oversized QTM rotor on the front. Similar to the overbore, the gains in braking performance are difficult to decipher considering how excellent the standard CRF pinchers are.
Retro-styled graphics from Flu Designs made our test bike stand out in the looks department as well.
Works Connection is responsible for making this gem sparkle with an assortment of anodized tidbits. Our little white lie got an appropriate wardrobe with Cycra’s white Powerflow plastic and matching radiator hoses from CV4.
Racing a 250F can be a nightmare or a joy depending on your goals, size and how much money you’ve got to throw at it. Lots of 250F riders are just looking for that little extra from their ride, and until
Honda builds the perfect blend of power and agility, Jay Clark Enterprises has a good handle on how to bridge the gap. He’s got years of experience and a willingness to work on any brand of motorcycle. Find him at
www.jayclarkent.com.
