MOTOCROSS ACTION MID-WEEK REPORT
#WHIPITWEDNESDAY
Rider: James Stewart
Bike: 2006 factory Kawasaki KX450F
TWO-STROKE SPOTLIGHT: TYLER SMITH 2006 YAMAHA YZ315 STROKER
The before picture of the beat-up old dog.
“I am a lifetime MXA guy, 33 years old and reading since the ’90s. I read MXA as a kid and memorized a lot of issues growing up. I was out of riding MX for 10 years, mostly was doing superbike racing. Found some new friends that wanted to ride, so picked me up a beat-up 2006 YZ250 with a ton of hours.
Took it down to the frame and completely rebuilt it from the ground up. Talked to Tom Morgan about doing a YZ295 (top end only) and did that. Found out the bottom is a bit toasted, so he recommended doing a 315 stroker. It’s a 450 killer now, runs on 50/50 race gas and has a decomp lever. Tom has a dyno and this bike should put out 57-60HP to the dirt (44 stock on his dyno). I’m also in SoCal if you guys want to try it. ”
The after photo.
Full list of parts:
-Tom Morgan YZ315 Stroker, balanced and lightened crank, blue printed and hand ported
-Tom Morgan Carb tapered 41mm and bench flowed and hand ported
-Tom Morgan Vforce 3 bench flowed and hand ported
-Tom Morgan modified clutch for easier pull
-Enzo suspension
-DEP pipe
-PC 304 silencer
-11oz FWW (pretty needed with YZ315)
-Magura Hydro clutch
-2018 Yamaha wheels
-Starcross 5 Soft tires
-Cycra restyle
-Red Label Graphics
-YZ450F footpegs
-Primary drive chain/sprockets
-Hammerhead +20mm shifter
-Tusk brake lever
-2008 CRF450R front master cylinder and caliper, Honda pads
-Stock 270mm front rotor
-Galfer SS front brake line
-Luxon clutch cover
-Topar Ignition cover
-Nihilo frame grip
-Guts seat and seat cover
-ProTaper Contour SX bend
-Drilled airbox (315 stroker needs air)
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.
2022 KTM 350SXF TESTED
MOTO | TRIVIA
Who is this rider? Answer at the bottom of the page.
2022 AMA PRO MOTOCROSS SCHEDULE
2022 SUPERCROSS SCHEDULE
BE THERE! 2021 SOUTH CAROLINA STATE MX CHAMPIONSHIP
ASK THE MXPERTS: WHAT’S HOTTER? AN NGK BR9ES? OR WHAT?
The inside of a spark plug is less than exciting—so stay out of there.
Dear MXA,
My local shop mechanic suggested that I run a hotter plug in my well-used 2006 Suzuki RM125. I nodded, but after he walked away I realized that I didn’t know what he was talking about. I currently have an NGK B9ES plug. Is that hot?
The heat range of a spark plug is indicated by the number in the plug’s identification sequence. On NGK spark plugs, the lower the number the hotter the plug (higher numbers are colder). Thus, your NGK BR9ES is colder than a BR8ES. There are spark plug brands where the numbering system is reversed and the lower numbers are cold and higher numbers are hot, but not that many motocross racers use these plug brands (Champion, Autolite and Bosch). It should be noted that the terms “hot” and “cold” do not refer to the temperature of the plug’s actual spark but the speed at which the plug transfers heat from the combustion chamber to the engine head.
Autolite plugs have the opposite heat ranges of an NGH plug.
When a spark plug is referred to as a “cold plug,” it is one that transfers heat rapidly from the firing tip into the engine’s head. The rapid heat transfer keeps the firing tip cooler. A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter. The difference from one full heat range to the next is the ability to remove 158-degree to 212-degree Fahrenheit from the combustion chamber. The primary factors that affect a spark plug’s heat range are the internal length of the core nose, the alloy compositions in the electrode and the amount of porcelain insulation.
We don’t know what your mechanic saw in your engine, but most likely it was carbon build-up, soot or combustion deposits on the plug or the combustion chamber. It should be noted that the 2006 RM125 came with a very expensive NGK R6918B-8 spark plug. Although it was a better-engineered plug, it didn’t necessarily make the engine run any better. It was really spec’ed on the RM125 because there were issues with the electrode strap breaking off on the standard-issue BR9ES plugs. In 2006, MXA ran an NGK BR9EVX plug. We had no issues with the BR9EVX’s electrode strap, but we changed the plug at regular intervals.
MARK BLACKWELL RECEIVES EDISON DYE LIFETIME ACHIEVEMENT AWARD
FORGOTTEN BIKES: 2000 HUSQVARNA TE410
FMF VISION READY TO SUPPORT PRIVATEERS
Privateer Power Program Offers Contingency Money to Professional Racers.
Press Release: FMF has always supported the hard-working, journeymen heroes of the sport. For 2022 FMF VISION is ready to extend that initiative by offering financial support to AMA Supercross and Motocross athletes.
Introducing the FMF VISION Privateer Power Program:
The FMF VISION Privateer Power Program allows professional Supercross and Motocross athletes to get FMF VISION sponsorship, engage in FMF’s marketing platform and make contingency dollars for their performance and hard work.
2022 Contingency:
Per each event final overall finish position.
| AMA 450SX | AMA 250SX | AMA 250/450MX |
| $500.00 : Main Event Top 10 | $200.00 : Main Event Top 10 | $200.00 : Overall Top 10 |
| $200.00 : Main Event 11-22 | $100.00 : Main Event 11-22 | $100.00 : Overall 11-20 |
To Apply:
Riders must complete the online registration form prior to the season and be accepted to be eligible for contingency payout.
https://apparel.fmfracing.com/collections/vision
Program Details:
Upon approval to the program:
- Rider must wear FMF VISION goggles exclusively throughout entire season
- Rider must wear FMF VISION goggles throughout the entire event; practice, qualifying and all races
- FMF VISION goggles must remain unaltered with original logos, colors and branding
- Rider must start and complete more than 50% of main event to be eligible for payout
- Rider must tag @FMFvision in social media posts a minimum of once per month
- Rider must fill out contingency claim form (provided upon acceptance) at end of season and provide W9 for payment to be processed
Visit www.FMFRACING.com for more information. Follow @fmfvision for the latest updates
SUZUKI RM-Z450 PRO CIRCUIT T-6 EXHAUST SYSTEM
By Brian Medeiros
What’s up Motocross Action! It is no secret that the 2019 RM-Z450 lacks that “get up and go” feel on the low end of the powerband. This is really noticeable on tight corners and “S” turn sections where you would really have to be on the clutch to get the bike up and out of the corner to either set up for the next jump or corner. We gave the guys at Pro Circuit a call to see if they had a solution and we were able to get our hands on their stainless steel T-6 Exhaust System. On the track, it gave this bike the excitement that we were looking for. We were able to take advantage of the great turning characteristics of the RM-Z 450 knowing that we now had the power to pull out of corners without having to rely on the clutch.
Is it rip your arms off power? No, but it is definitely a noticeable difference over the stock system. We also noticed a difference in the over-rev of this bike. With the stock system we felt that once you got up in the rpm, just before the rev limiter, this bike would fall flat. With this Pro Circuit T-6 System, we were able to pull third gear far enough to get to the end of long straight always without having to upshift to the next gear and then downshift right away for the corner ahead.
So if you are looking to give your RM-Z450 a little pep in its step give the guys at Pro Circuit a call at 951-738-8050 or visit their website www.procircuit.com to get yourself dialed in. We will have a full test of the Pro Circuit RM-Z450 exhaust in a future issue of MXA.
CLASSIC MXA PHOTO
Jeremy McGrath racing the 1999 Summercross at the L.A Coliseum which he lost to his Yamaha teammate Tim Ferry.
Moto Trivia answer: Ryan Mills.
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