MOTOCROSS ACTION MID-WEEK REPORT

#WHIPITWEDNESDAY

Adam Cianciarulo_2019 Denver Supercross-4812

Rider: Adam Cianciarulo
Bike: 2019 Pro Circuit Kawasaki KX250
Location: Denver, Colorado Supercross
Photographer: Brian Converse

TWO-STROKE SPOTLIGHT: DOUG DUBACH’S 1983 YAMAHA YZ100

dubach_1983-yamaha-yz100 This week two-stroke spotlight belongs to Doug Dubach’s 1983 Yamaha YZ100. Read below to find out why.

_an28386_lrBack in the day, racetracks were filled with 100cc bikes, with everything from Novice to Pro classes. That time has long since passed, but 100cc two-strokes still have a place in racing, thanks to the Marty Tripes 100cc Works Revenge Series. The rules are rather basic: the engine must be 100cc (bored no more than 2mm over); no water cooling; the frame must be from 1983 or earlier. However, the frame can be modified or made from hand. Other than those few mini moto laws it’s fair game for anything under the sun. Doug Dubach, with the help from his friends, crafted a ridiculously cool 1983 Yamaha YZ100.

The engine is stuffed with a Wiseco piston, REM-coated gearbox, Barnett clutch, Moto Tassinari reeds and 34mm Keihin PWK carburetor. A gusseted frame, CRF450 footpeg mounts, IMS pegs and an aluminum Yamaha IT175 swingarm are also on the YZ100 conversion. In my eyes the coolest parts on the bike are the hand molded carbon fiber gas tank, number plates, chain guide and airbox cover. What can I say, I’m a sucker for carbon fiber.

_an28377_lrDubach’s 1983 Yamaha YZ100 was a blast to ride. You had to fight the urge of hitting the brakes for fear of slowing momentum, because the engine isn’t a modern pony pusher. It was no surprise that Doug Dubach could fly around the track on his YZ100, just as long as the hills weren’t too steep. Watching “The Doctor” tear around on 36 year old bike was like traveling back in time.

Editors 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. Please don’t email me spam or try selling me Taylor Swift concert tickets or email me spam. Happy submitting your smoker.

MOTO | TRIVIA

 Mark Barnett 1984Who is this rider? Answer at the bottom of the page.

HAIDEN DEEGAN ON HIS STAR RACING YZ250F

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NIHILO CONCEPTS GRIP DONUTS 

DUBYA VET WORLD CHAMPIONSHIP VIDEO // MXA EXCLUSIVE

MXPERTS |CERAMIC BALL BEARINGS

MXPERTSbearing33
Dear MXA,
What is the deal with ceramic ball bearings? Wouldn’t they be perfect for motocross bikes?

Ceramic bearings are actually hybrid bearings because only the balls are made from the nonferrous ceramic material (although there are ceramic races, but only for special uses). Everything else on the bearing is identical to a standard bearing. The ceramic bearing ball is formed through the action of heat, just like making a ceramic coffee cup. A ceramic ball begins as a fine silicon nitride Si3N4 powder. Under heat and extreme pressure the Si3N4 powder is formed into a bearing ball. The key to its toughness is the sphere shape; it perfectly contains the high-pressure innards. A ceramic bearing ball has twice the Rockwell hardness of steel. Once shaped into a ball it is the third hardest material known to man, following diamond and cubic boron nitride.

MXPERTSCeramic-Balls

A ceramic bearing ball is 2/3rd’s the weight of a steel ball. The surface of the ceramic ball is nonporous and mirror-like. In comparison, a magnified steel ball looks like the surface of the moon. Ceramic is not an oxide and thus cannot rust. The synthesized ball is very resistant to wear and abrasion. It also has very low deformation under load and very low thermal expansion. By themselves the ceramic balls are so smooth, indestructible and glass-surface perfect that they do not need lubrication. But the steel races they ride in do.

A Si3N4 ceramic ball is 1000 times more precise than a steel ball and is preferred in high-precision CNC machinery. Ceramic bearings are the choice where excess bearing heat due to high shaft speed is an issue. The spin rating of some ceramic bearings is as high as 300,000 rpm and easily ten times faster than the best steel ball bearings.

As far as motocross use goes, some factory and privateer teams do use ceramic ball bearings. As a rule they use them in places where the light, ultra-smooth and perfectly round balls make it easier for the bearing to acceleration. The light and smooth balls spin without hesitation and drag. By reducing bearing drag you create horsepower. A ceramic bearing here and there, like on the crank, won’t make much of difference. But, the cumulative effect of ceramic bearings on every turning spindle, axle and shaft in the drive train, as well as in the wheels, can make a noticeable difference. Used in unison they could reduce friction by one to two percent—which may not sound like much, but could equal a half horsepower gain on a 250 four-stroke. That is an easy horsepower gain.

It is however not a cheap horsepower gain because ceramic bearings cost three times more than the most expensive steel bearings. For example a steel crank bearing will cost $20, while a ceramic bearing will run $85. For a factory team the cost of ceramic would spread across four race bikes and eight engines (at least). And since those race bikes are typically torn down every two hours, the cost could run to several thousand dollars in a 29-race season.

FORGOTTEN BIKES: KELLY SMITH’S 2004 YAMAHA OF TROY YZ250F

Kelly smith 2004 yz250f

HAVE YOU SEEN THE DECEMBER 2021 ISSUE OF MXA? IT IS THE BEST DEAL IN THE SPORT!

If you don’t subscribe to MXA, you are missing a whole different world of motocross news, facts, test and photographs. For example, the just released December 2021 issue includes a complete and thorough test of Andy Jefferson’s 2022 GasGas MC366F. You read that right! It has a 366cc engine that has more torque, without giving up any of the revs of a traditional 350cc engine. In the same note, MXA’s Josh Mosiman decided to race the Hangtown National to see if he could qualify for the “Fast 40” after two years off the circuit. No big deal given the Josh has raced lots of Nationals before, but this time he decided to do it on a box-stock 2022 KTM 450SXF—stock engine (no pipes, ignitions or pistons), stock forks (right off the showroom floor), stock WP shock (not even a spring change). He only made two changes—he installed a Guts Wing seat and Jody made him run Husqvarna Rockstar Edition wheels. Read his story to find out how he and his stocker fared. When you’re done reading the bike tests (2022 CRF250, KX450, TC125 and YZ250F), you might want learn a little bit about the famous “Junkyard Dog.” We track down John Dowd for a full rundown on his racing career and what he’s doing now. Plus, much, muh, much more.

HOW TO SUBSCRIBE TO MXA SO THAT YOU NEVER MISS ANOTHER ISSUE, PLUS GET A $25 ROCKY MOUNTAIN GIFT CREDIT TO COVER YOUR COSTS

You can’t afford not to subscribe, because when you get order a $19.95 subscription, Rocky Mountain ATV/MC sends you a $25 gift credit to use on anything you want from their massive selection. Plus, subscribers to MXA can get the digital mag on their iPhone, iPad, Kindle or Android by going to the Apple Store, Amazon or Google Play or in a digital version. Even better you can subscribe to Motocross Action and get the awesome print edition delivered to your house by a uniformed employee of the U.S. Government. Do we have to mention the $25 Rocky Mountain ATV/MC gift card again? You can’t lose on this deal? Call (800) 767-0345 or Click Here (or on the box at the bottom of this page) to subscribe.

HONDA CR-E PROTOTYPE CLOSE UP SHOTS

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BAM TV // BATTLING ON THE SUPERCROSS TRACK

THOR EXTENDS CONTRACT WITH AARON PLESSINGER

Press Release: THOR is thrilled to announce a multi-year extension with elite factory racer Aaron Plessinger as he enters the 2022 Supercross and Outdoor Motocross season, aboard a new bike and backed by a new team. Headed into his seventh year with the brand, Aaron has consistently represented THOR racewear in a positive and professional manner. THOR is excited to continue this multi-year relationship with Plessinger, utilizing his adept riding abilities, and valuable input to enhance THOR’s premium product line.

Aaron is headed into the 2022 Supercross season aboard a new machine that’s backed by the Red Bull KTM Factory Racing team. Aaron will be under the same tent as teammate and THOR athlete, Cooper Webb. Plessinger, a THOR athlete since 2016, is a fan favorite for his distinct style on the track and All-American attitude off the track.

Plessinger enjoyed a successful 250 career with THOR MX winning the West Coast 250 Supercross Championship as well as the 250 Pro Motocross title in 2018. That success and support propelled Plessinger into his 450 career in 2019 where he bagged numerous top-10 finishes along with one career top-five and now has his sights set on the 2022 SX season.

The 2022 AMA Supercross Championship kicks off on Saturday, January 8 in Anaheim, California where we hope to see Plessinger at the top of the 450 class, sporting his signature hairstyle and refusing to hold back as “America’s Mascot”. Get ready to witness Aaron firing up the crowd with the loud roars from his factory 450 engine and his long luscious locks flowing from out the back of his helmet.

AARON PLESSINGER KTM 450SX-FAaron on his new KTM ride. 

About THOR Motocross: THOR was founded by 4-time World 250cc Motocross Champion, Torsten Hallman, in 1968 in San Diego, California. Over the decades, countless races and championships have been won by riders wearing THOR. Every product is a progression, a new step forward in design and performance. Always racing forward, always respecting our past, always focused on building quality products that exceed rider expectations. To see what’s new, visit your local authorized dealer or www.thormx.com

The First, The Forever…Torsten Hallman Original Racewear.

TESTED // 2022 GASGAS MC 450F //MXA

9TH ANNUAL KURT CASELLI RIDE DAY 

CLASSIC PHOTO

Ryan Dungey 2016 450 start glen helenRyan Dungey taking the holeshot at the 2016 Glen Helen National.

Answer: Mark Barnett

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