MOTOCROSS ACTION MID-WEEK REPORT

#WHIPITWEDNESDAY

TWO-STROKE SPOTLIGHT: CURT WINTER’S JAPANESE BLEND

I was initially worried about featuring the “Two-Stroke Spotlight,” because I was unsure whether Mid-Week Report readers would submit photos and descriptions of their bikes. Fortunately, my inbox has been flooded with awesome two-strokes. Thanks for taking the time to send over info on your prized iron. I have to give a special nod to Curt Winter, who deservingly earned this week’s honor with his Yamaha/Suzuki/Honda amalgamation. Take it away, Curt.

“Hi MXA, I saw your article on the Honda CR500 AF. I’ve built and owned several of those and have always been a Honda guy, but I wanted something different. 500 AFs are everywhere, so I built something different. I bought a well-used 1987 Yamaha YZ490, stripped it down to the frame and started the build. I graphed on rear suspension from a 2007 Honda CRF250, including the rear disc brake. In an effort to retain the old-school look I opted for a set of 1997 Suzuki RM250 forks. I rode and raced it for a while, but never really liked the shortcomings of the Yamaha motor. For that reason, I installed the complete top end from a 1984 Honda CR500 (air-cooled) on a 1990 CR500 lower end and slapped that motor in the YZ chassis. Now it’s got a motor worthy of the better suspension. I currently race it against modern bikes and have a blast. Truth be told, I was surprised how well it worked.”

Editor Note: 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 thing. 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. 

MXPERTS //“WHAT HAPPENED TO LEADED GASOLINE?”

Most two-stroke motocross racers get their leaded gas from VP race fuel or 100 Low Lead airplane fuel. It should be noted that there is nothing low lead about airplane fuel.

“WHAT HAPPENED TO LEADED GASOLINE”

Dear MXA,
The gas station down the street used to sell leaded gasoline when I was a kid. They called it “high test leaded.” I ran that in my minicycle until it disappeared. What happened to leaded gasoline?

Way back in 1923, a General Motors’ engineer discovered that adding tetraethyl lead (TEL) to gasoline raised the octane number. Early automobiles had very basic ignition and electrical systems, and “knocking,” what motocrossers call “pinging,” was a very real issue. Thus, tetraethyl lead was added to America’s fuel supply as an anti-knock additive—with the added benefit of the lead cushioning the valve seats. The lead allowed for high compression and more power from automobile engines; however, lead is very toxic, and exposure to it leads to cardiovascular and immune system problems (remember the scare about kids in urban areas eating paint chips off their bedroom walls and getting lead poisoning?). The fact that tetraethyl lead was unhealthful was not a secret to the automobile or oil industry, and the engineer who invented leaded gasoline eventually suffered from lead poisoning himself. But, the danger to humans was not the reason leaded gasoline was banned in the United States. Instead, it was the danger that leaded fuel posed to the newfangled catalytic converters that were mandated in the Clean Air Act of 1970. Leaded fuel stopped catalytic converters from cleaning the pollutants that were emitted out of the exhaust pipes. Thus, by 1975, every car sold had a catalytic converter, hardened valve seats and a sticker inside the fuel door that stated “unleaded fuel only.”

Leaded fuel was still sold at gas stations to supply the aging fleet of non-catalytic converter cars until 1992 when California banned the sale of unleaded fuel for road-going automobiles. The rest of the nation followed suit in 1996. The move to unleaded fuel was hectic at first, as fears of valve-seat issues and pinging kept drivers of older vehicles on edge (and many had their cylinder heads modified for less compression); however, modern ignitions have all but eliminated the concerns.

LOST BUT NOT FORGOTTEN | 1996 KAWASAKI KX250

INSIDE KEN ROCZEN’S FACTORY HRC CRF450

AT THE BREAK SUPERCROSS STATS // By Ben Bridges

450SX STATS

Eli Tomac:

Jason Anderson:

Justin Barcia:

Malcolm Stewart:

Cooper Webb:

Marvin Musquin:

Chase Sexton:

Dean Wilson:

Dylan Ferrandis:

Brandon Hartranft: (11^th in points, Ken Roczen is 10^th and out for season)

250SX WESTERN REGIONAL

Christian Craig:

Hunter Lawrence:

Michael Mosiman:

Vince Friese:

Jo Shimoda:

250SX EASTERN REGIONAL

Jett Lawrence:

Cameron McAdoo:

Pierce Brown:

RJ Hampshire:

Enzo Lopes:

MOTO | TRIVIA

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

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CLASSIC PHOTO

Ryan Villopoto back in 2013 where he won 10 450 SX main event to go on to win the Championship.

Moto Trivia answer: Rodney Barr.