MOTOCROSS ACTION MID-WEEK REPORT
#WHIPITWEDNESDAY
Rider: Justin Hill
Event: Round 1 WSX series 2023
TWO-STROKE SPOTLIGHT: SAUL RUIZ 2007 SUZUKI RM250
Hey MXA, I just got done with a two-stroke build for the MTA Two-Stroke National. It’s a 2007 Suzuki RM250. We called it Project Wrekt. The bike has Raptor foot pegs, Hammerhead shifter and brake pedal, Hinson clutch, custom N-style graphics, Showa forks (Michael Byrne’s diamond kit from one of his practice bike RG3 suspension), Applied triple clamps with updated front end and Excel rims with Talon hubs.
This is the cover of the August 2023 issue of MXA. On the cover is Pro Circuit’s Yamaha YZ125 project bike and the 2023-1/2 GasGas’ MC450F Factory Edition. Inside are full-length tests of the 2023 Honda CRF450WE Works Edition (not to mention the 2023-1/2 MC450F Factory Edition) and a retro test of the 1999 Suzuki RM250 two-stroke. We take a close-up look at the 1976 Yamaha OW25—a bike that has a unique history because before the start of the 1976 racing season, Yamaha pulled out of racing—leaving their American (and GP teams) to fire their veteran riders go and bring in three relatively unknown and lower-paid youngsters. The three USA riders were Rick Burgett, Danny Turner and Bob Hannah. Additionally, the MXA wrecking crew headed to Japan for the Kamisu City Beach Race (with a side trip to the Honda Museum). There is so much more inside. Did we mention the indepth interview with Brian Deegan? You’ll never know how much you have missed if you don’t subscribe? Plus, you can subscribe without it costing you a cent!
The MXA wrecking crew is everything moto related. Check out our 
MOTO | TRIVIA
Name the rider. Answer at bottom of page.
QUOTE OF THE WEEK // TOM VIALLE ON SOUTHWICK IS NO LOMMEL
The track was nice. Maybe a bit more similar or familiar to some of the tracks I raced on previously in the GP’s. As I said, I felt very comfortable, maybe more so than with previous tracks. It may be considered a sand track, but in no way is it Lommel.
Read the full interview here
INSIDE RYAN HUGHES’ SPILTFIRE PRO CIRCUIT KX125 FROM 1994
DO YOUR KTM AIR FORKS HAVE AN AIR LEAK? NO, THEY JUST NEED A LITTLE PUSH
Dear MXperts,
I bought a new KTM 350SXF, and two days later, I went out to the garage and the forks collapsed. I pumped them back up, but it didn’t help. Is there a simple fix for this problem?
Yes, there is, and we will tell you what it is after we explain how and why your air forks could collapse without you riding the bike.
Air forks have two separate air chambers with their own unique air pressures. The top air chamber, known as the main chamber, pushes the fork downward to resist the forces imparted when hitting bumps or landing from jumps. It is simple to understand because it works identically to a steel coil spring. It is possible for the main chamber’s air pressure to create a condition known as “topping out.” Topping out is caused when the forks are fully compressed and the air pressure inside the forks exerts its pressure in the opposite direction of the main chamber’s air. In short, the compressed air in the forks makes the forks extend rapidly back to their full length. It is called “topping out,” because when the forks extend to their full length, they make a clanking noise when they hit the end of their stroke.
The solution to “topping out” on air forks, especially the Kayaba PSF and Showa SFF-TAC air forks of 2015–2018, was to add a second air chamber on the opposite side of the over-pressurized main chamber. The air pressure below the main chamber was used to stop the forks from topping out on the rebound stroke. This second chamber was called the negative chamber. On Showa and Kayaba’s air forks, it actually was a second chamber with its own piston and Schraeder valve to tune it. But, it was a nightmare to deal with and eventually Showa and Kayaba gave up on their production air forks.
KTM, on the other, didn’t jump blindly into the air-fork craze. Instead, KTM watched the Japanese fork brands crash and burn, and then came out with an ingeniously simple idea‚ especially when compared to the complicated balance chambers of Showa and Kayaba air forks. KTM’s concept was to harness the air pres sure in the main chamber to do double duty. Basically, they use the main chamber as the negative chamber
Now to answer your question about a “simple fix.” WP forks can go flat when they are left sitting. It is not common, but it does happen. Why? The air in the main chamber leaks into the negative chamber through the cross-over bleed slot, and the unbalanced air pressure pulls the fork tubes up. The simple fix is to cycle the fork legs up and down so that the pressure in the negative chamber can transfer back to the main chamber, and when it does, the forks will extend to their full length; however, it often requires two or more people to cycle the forks up and down over their full length. One person sits on the bike and pushes the forks downward, while a second person straddles the front wheel, helping apply even more downward force.
Once you get the forks going in a rocking-horse motion, the air trapped in the negative chamber will cycle through the cross-over bleed slot over to the main chamber, bringing the forks back to their original length. All you have to do is reset the air pressure and take the bike for a short test ride.
CLASSIC PHOTO
The coolest Caddy you will ever see.
Moto Trivia answer: Eric Sorby.
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