MOTOCROSS ACTION MID-WEEK REPORT
#WHIPITWEDNESDAY
Rider: Justin Cooper.
Justin was another one of those riders who was not a top mini rider in amateur racing but once moved to big bikes he began to have more luck and in his final years of A-class, he dominated every national he attended. Growing up in New York he lived coastal and there were not many tracks in his area. He began traveling to different events gaining experience. Once moving through the ranks he raced A-class at all the major amateur events. He won Loretta Lynns in both Open Pro Sport and 250 A. At mammoth motocross that same year he won every moto by almost thirty seconds and was the most dominant rider that weekend. Once going pro he raced his hometown national at Unadilla, he placed fifth overall in his first national and the success started there. The following year he had multiple podiums and has become the dominant rider we see today.
NO DAYS OFF
Having a two-weekend break you’d assume that the riders would take some time to rest and recover from the season thus far. But as for Jason Anderson, he was out in the 100-plus-degree weather at Glen Helen Raceway, putting in his thirty-minute motos. In motocross there really are no breaks, there is always a rider training harder and if you were to spend time off the bike you would give the advantage to them. As the motocross season will head directly into the SMX rounds, the riders basically have an all-year season of racing, and as soon as SMX is over they will begin training for the upcoming 2025 Supercross series.
ROCZEN RETURNS AT UNADILLA
Ken Roczen posted a statement earlier this week to his social media, notifying that he would be returning to action at the Unadilla National and that the progress from his leg injury at the Nashville Supercross has been going well. He said that he would be racing the 450 class at Unadilla but a surprise came when he said that he would be riding in the 250 class at the Ironman National to finish off the motocross series. It has been eleven years since Roczen has raced a 250 and it will be interesting to see how he stacks up with the young up-and-comers.
HOW DEEGAN WILL (LIKELY) WIN THE CHAMPIONSHIP EARLY
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MXA PHOTO TRIVIA
Who is this rider? Answer at the bottom of the article!
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ASK THE MXPERTS: WHAT IS A DESAXE ENGINE?
Modern 450 cranks are offset 0mm, 4.5mm, 5mm. 8.5mm and 12mm depending on brand.
Dear MXperts,
I learn new stuff every time I read an issue of MXA. Is it true that the piston, wrist pin, crankshaft and cylinder bore do not line up vertically on modern four-stroke engines? That is contrary to what I learned in auto shop at school. True or false?
It is true. Engines with the cranks offset from the cylinder’s center line are called “desaxe” engines. Desaxe, the French word for “unbalanced,” describes an engine in which the cylinder is positioned with its exact center (the bore axis) offset from the center line of the crankshaft. Desaxe engines have been around for a long time, even Henry Ford implemented offset cranks on the Ford Flathead V8 in the 1930s. Motocross engines have been adopting offset cranks for the last 15 years.
Ultimately, the object of a desaxe engine is to produce more power with less friction. Since the compression stroke occurs on one side of the crank’s rotation and the power stroke on the other, offsetting the crankshaft to one side makes it possible to achieve both a loss of friction on the up stroke and a power advantage on the down stroke. When the crank is offset, the piston’s down force is directed in a straighter line from the piston through the connecting rod to the crankshaft. Instead of pushing the rod at an extreme angle, the rod’s relationship to the crank is less severe, thus more efficient on the power stroke.
As a rule of thumb, less crank offset affects higher rpm ranges, while more offset has its greatest effect at lower rpm. Thus, when Yamaha chose a 12mm offset for the YZ450F engine, they were using test rider input and computer modeling to get the type of power they wanted. It should be noted that there is a point of no return. Yamaha chose 12mm, but that does not mean that 15mm would be even better. In fact, the Suzuki RM-Z450 uses 0mm crank offset, and the Honda CRF450 has 4.5mm of offset. The Kawasaki has 8.5mm of offset, and the three Austrian engines share 5mm of offset.
In a conventional four-stroke engine, each of the strokes (intake, compression, power, exhaust) involves a nominal rotation of 180 degrees, totaling 720 degrees for the complete four-stroke combustion cycle. A desaxe engine adds to the duration of the two downward strokes (intake and power) and subtracts the same amount from the two upward strokes (compression and exhaust), with the total remaining at 720 degrees. A typical desaxe engine will have strokes of 185, 175, 185, and 175 degrees, with the degrees as a percentage of offset distance to stroke length.
How are cranks offset? It can be as simple as having the crank aligned with the center line of the cylinder and offsetting the piston with an eccentric wrist pin. In 2009, Yamaha wanted the benefits of offset cranks for the YZ450F but didn’t want the cost of new cases. So, Yamaha used a 1mm-offset piston wrist pin to move the centerline over 1mm; however, you can’t get 8mm, 10mm or 12mm of movement from an offset wrist pin. That necessitates a more complex solution, often requiring casting offset engine cases.
If you’d like to read more MXEXPERTS posts, click here.
WHAT WE REALLY THINK ABOUT THE 2024 BETA 450RX
QUOTE OF THE WEEK: KAY DE WOLF WINS MXGP OF FLANDERS
“It was a really positive weekend overall. The thing is, that each weekend we are trying to get as many points as possible, and preserve our position at the top of the championship. Sometimes that doesn’t mean winning every single moto. I have to be critical also because the second moto wasn’t good enough – I made too many mistakes, which shouldn’t have happened – so I will for sure be working on that. I’m happy to finally win Lommel – I can’t thank the team enough, I think the timing is really great too. Having everyone here, just two minutes from the workshop, and with the news on Friday that Husqvarna is staying. Now we look ahead to Sweden in two weeks, and will keep pushing!”
MXA PHOTO OF THE WEEK
CLASSIC MXA PHOTO
Billy Laninovich showing some style on his Amsoil Honda. This is the team that would form into Gieco Honda before folding just a couple years ago. Laninovich was the winner of the San Francisco Supercross.
MXA Photo Trivia Answer: Mike Brown who had one of the longest racing careers of any rider and won the 2001 motocross 125cc championship. Mike still races vet classes today and is still one of the fastest riders on the track.
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