MOTOCROSS ACTION MID-WEEK REPORT

On Apr 26, 2022 Last updated Apr 26, 2022

#WHIPITWEDNESDAY

Rider: David Vuillemin
Bike: 2004 Factory Yamaha YZ250
Photographer: MXA Archives

TWO-STROKE SPOTLIGHT: MATTHEW WESTBURY’S 2000 KAWASAKI KX250 PRO CIRCUIT/SPLITFIRE REPLICA

“Here is my 2000 Splitfire Kawasaki KX250 that I am almost done building. Thought you guys would enjoy.” –Matthew Westbury.

Editor’s Note: Please keep those submissions coming. If you would like your bike to be featured in the “Two-Stroke Spotlight,” please email me at [email protected]. All I ask is that you give a breakdown of your bike and a detailed description of the build. Please also send a few photos of your steed. By submitting your bike for the “Two-Stroke Spotlight,” you agree to release all ownership rights to the images and copy to MXA.

INSIDE THE ALMOST FACTORY JORDON SMITH FIRE POWER HONDA CRF250

PRO-VUE PRESCRIPTION GOGGLES

Pro-Vue has been making prescription goggles since 1989. Their unique patented design is the only prescription lens system that attaches securely in the goggle. Pro-Vue uses 100% goggles exclusively, and they offer five frame colors as well as about a dozen different tinted goggle lenses in addition to clear.

The price for a complete, ready-to-wear prescription goggle starts at $219. See everything at pro-vue.com or call or text Randy at (507) 534-1247.

Pro-Vue Prescription Goggles
pro-vue.com
Pro-Boot MX Resole & Repair
pro-bootmx.com

MOTO | TRIVIA

Name the rider and year. Answer at bottom of the page.

EVERYTHING YOU MISSED ABOUT FOXBOROUGH SX IS RIGHT HERE

Click here for everything you missed from the Foxborough Supercross.

TALK MOTO WITH ON MXA’S FACEBOOK GROUP CHAT

We love everything moto and want to bring all moto junkies together into one place to share their two cents, ideas, photos, bike fixes, bike problems and much more. To check it out first you must need to or already have a Facebook account. If you don’t, it isn’t much work and you could even have an alias so nobody knows it is you. To join click HERE. After you request to join we will accept your request shortly after.

JOSH MOSIMAN’S TAKE AND EXPERIENCE OF THE WORLD 2-STROKE NATIONAL

AN OVERVIEW VIDEO OF THE 2022 WORLD TWO-STROKE NATIONAL AT GLEN HELEN

MXA QUOTE // JETT LAWRENCE TALKS ABOUT WINNING THE 250 EAST COAST CHAMPIONSHIP

To be honest, I was calmer than last weekend, going into the East-West Showdown. I was just enjoying it, and that helped me have more fun with the track. In the main event I got out of the gate okay, but I was a bit off balance. I lost all my traction there, but I was just happy to make it through the first turn. I liked battling with Austin [Forkner]; I think it helped me to not even worry about the championship, because I was more excited about the race. I tried some different lines, made some mistakes, but this track was so about being consistent. I’ve dreamed of this since I was a little kid. All the hard work that we and the team have put in, and all the hard times I’ve gone through – this one night makes all that disappear. I just have to say thanks to the team. I wouldn’t be here without my brother; I feel like he should have a number 1 plate too, because he’s a big part of this. This one is definitely a lot more than the outdoors [title]; I’ve had a lot of rough runs in supercross, so this is unreal.

MXPERTS | THE UNINTENDED CONSEQUENCE OF GOING BIG

On MXA’s project KX250F we switched to a 2.15 rim and ran a 110 rear tire. It is a good mod if you have the power to pull it and the knowledge to compensate for it.

Dear MXA,

I read the article on “How to Make the 2018 KX250F Better.” You mention using a set of KX450F rims, but you didn’t address the rear tire sizing issue. My KX250F came with a 100 rear tire on a 1.85 rim. I get the impression that you ran a 2.15 rim and 110 rear tire. Is it okay to run the 110 tire on the narrow 1.85 rim?

It can be done, but it is much better to do what we did, which was switch to a 2.15 rim. Running a 110 tire on your stock KX250F’s 1.85 rim will work, but the typical 110/90-19 tire is designed for the 2.15-wide rim. Wedging a 110/90-19 onto a 1.85 rim will squeeze the larger tire where the beads meet the rim, producing not only a much rounder tire profile but also a much taller rear tire. If you could find a 110/80-19 rear tire, the rounding and height effects would be reduced, but you probably will not be able to find a 110/80-19 rear tire in a premium brand.

Lots of riders do run 110 tires on 1.85 rims and claim that there is an increase in traction from the wider tire, but that is most likely an illusion created by the significant changes to gearing and frame geometry brought on by the larger-diameter rear tire. The increase in tire height will raise the gear ratios, much like taking teeth off the rear sprocket. It will also raise the rear of the bike, which will steepen the head angle. These unintended consequences can be worked out, if recognized, by gearing corrections and sliding the forks up and down in the clamps.

Why would the 110/80 work better than the 110/90? It comes down to the tire’s aspect ratio. The first number on the tire is its width. Width is measured in a straight line from the furthest point on one sidewall, across the tread, to the furthest point on the opposite sidewall. In our example, that would mean 110mm wide. The second number is the height of the tire—not in millimeters, but as a percentage of the first number. Thus, a 110/90 tire is 110mm wide by 90 percent of 110mm tall. The math works out to 110mm wide by 99mm tall. For comparison, a 110/80 tire is 110mm wide by 88mm tall. More significantly, your KX250F’s stock 100/90-19 rear tire is 100mm wide and 90mm tall. Making it a little more confusing is that putting a 110 tire on a 1.85 rim exaggerates the profile because of the ballooning effect of pinching the beads together. This makes the tire taller than its listed percentage.

If it were us and it was on this project bike, we would switch to a 2.15 and run a 110/90 tire, lower the gearing and move the forks to re-establish the proper frame geometry.

Send your questions in to [email protected]

INSTA CARNAGE // FOXBOROUGH SX

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CLASSIC PHOTO

This is the cover of the 1993 August issue of MXA. We were surprised that the cover-all shrouds did not become the look of tomorrow’s motocross bikes.

Moto Trivia answer: David Bailey 1985<

mid-week