Lee likes the top end power of Seth’s bike. We test the WBR Bulk Nutrients machine and hop on Seth Burchell's Yamaha YZ250F.
Every time you think motorcycle development has plateaued and ‘topped out’ a manufacturer finds a way to head off in a different direction and recreate the wheel to a certain degree. One of the manufacturers at the forefront of this development is the Yamaha Motor Corporation. With the success so far this year of the WBR Bulk Nutrients Yamaha team in Australia with their ProMX MX3 results, I thought it would be a solid idea to hop aboard one of their race bikes to get an insight into their current weapon of choice, the 2024 Yamaha YZ250F. The team owned the MX3 podium at Round 1of the Pro MX in Wonthaggi, Victoria finishing first, second and third and held down the red plate with championship points leader Koby Hantis after five rounds. I got the chance to hop on Seth Burchell’s Yamaha YZ250F after this round.
THE NUMBER 27 MACHINE
At just 18 years of age five times state motocross champion Seth Burchell is one of our stars of the future and has proved multiple times that he will be a force to be reckoned with for years to come and it is his bike I’m testing
Weighing in at 65kg and a height of 175cm Seth has a very traditional body position when riding. If anything carrying his weight a little off the back of the back which is reflected in quite a high set up for both the gear shift and back brake levers. Other than slightly raising his swept back handlebars I basically kept the bike as is for my test.
INITIAL LAPS
RidePark just outside of Bacchus Marsh was absolutely prime for testing with ruts and bumps still left in from the weekends riding. It’s an absolute monstrous track that would hold its own on the AMA circuit in America. A small sprinkle of rain overnight and we had ourselves moto heaven.
Anytime riding someone else’s bike is always an eye opener. Whether that is a new model at a launch, or someone’s pride and joy race bike. All of your systems are on alert for those initial laps and you have so much data processing in your brain. You’re trying not to be too judgmental during your warm up laps because let’s face it, everyone is different.
One of the main benefits in being a factory team rider is not the cool bolt on parts that make your bike noticeably better, it’s the options you have to fine tune your bike to your own desires. Choices are the luxury of the Factory rider and quite often these choices don’t suit everyone. I’ve found in the past that some of the weirdest set ups I’ve ever come across have been from some of the biggest name riders but all that matters is that it suits them.
The blue 250 four-stroke has a power curve that starts from midrange and winds its way up to a hectic, fire breathing weapon of a top end motor that seems like it would be competitive at the Calder Park drag strip. I scanned my memory back to a time when I got to ride Luke Clout’s Serco Yamaha YZ250F during a period where they were competing in the horsepower ranks here in Australia against the 250cc two-strokes. These two motors seemed like peas in a pod to me.
When you consider that Seth Burchell is only 65kg compared to my 85kg I have to think we have some serious peak horsepower going on here for a reasonably light lad.
Once I’d wrapped my head around the motor I found my attention wandering to the suspension setup and the Orange/Gold Ohlins componentry fitted. I’ve had quite a bit of experience riding with Ohlins over the years and always found them to be quite plush. True to form the suspension had a nice, smooth and planted feel while riding the RidePark circuit with the fork particularly impressing me with the balance between stability and hold up.
WHAT I LIKED
TOP END ROCKET
My favourite part of the bike would have to be the top end power on the right type of track. When I say this bike is fast, I mean lightning fast but it produces all of its useable power from midrange through to around 14,500RPM. For me it seems that a on sand track, or a relatively smooth track you’d really be able to use this top end power to the best of your ability without having to rely too much on the torque.
The 2024 YZ250F straight out of the crate is in need of a little extra torque but already has a strong upper midrange to top end power plant. The WBR race machines have a second injector via a GET SX1 ECU ignition which has added more top end power to an already abundant power plant. The VP Roo 100 fuel along with a high comp GYTR piston are designed to help power output right through the range combined with some in-house cylinder head work. Overall the power delivery is aggressive and needs to be revved exceptionally hard if you want to get the most out of it.
PLUSH RIDE
I was pleasantly surprised by the action of the suspension both front and rear. I was a little thrown in my initial laps by the balance of the bike front to rear however. I found myself loving the fork and thought this would be very similar to how I’d set this fork up myself.
The shock I found to be really quite soft and totally out of balance to the front. The action still worked well and soaked up everything nicely, from big hits to chattery bumps. With Seth weighing 65kg the rear of the bike seems to me like it should be very close to spot on for him. However the fork seems a bit on the firm side.
Either way, balance is critical for getting the bike to want to squat and turn in a corner and I feel that Seth may benefit hugely from softening the front a little. Or at the very least meet half way by firming the rear a tad and softening the fork ever so slightly. The fundamentals of a great set up are there and may just need a little tinkering.
FINISHING TOUCHES
Some of the nicest parts of the WBR Bulk Nutrients Yamaha are the little things. Stuff such as the EZE wheels sets, JT sprocket and DID ERT chain, the Ohlins suspension with its colourful coatings for less stiction, Zeta top clamp, Cycra plastics and Pro Taper handlebars. When you stand back a few metres and take a good look at the bike you really start to appreciate the finer details which all add up to one beautiful looking machine.
BRAKES
I found the brakes on Seth Burchell’s bike to be very similar to how I like mine, strong as all heck up front with nice feel out the back. The front brake runs an OEM caliper with ‘74’ coatings and a 270mm rotor giving exceptional power without losing too much feel. The team sticks with standard pads as they find this works the best for their riders. The rear brake runs a standard caliper with a 240mm rotor.
WHAT I WOULD CHANGE IF THIS WERE MY BIKE
TORQUE
Yamaha have gone down a slightly different path with their 250 this year and have sacrificed a fair bit of bottom end torque while achieving top end power gains. I would be chasing a tad more torque and rideability from the powerplant. Whether that is achieved by cylinder head porting, adding compression, ECU mapping or maybe a combination of all of the above I’m not sure. My main objective would be to gain torque while trying to maintain the incredible top end power.
BALANCE
This is heck of a lot easier than changing the power characteristics. I’d stiffen up the rear end and I’d be sorted immediately. The suspension package is already a very solid platform and just needs a bit of tweaking to the overall balance of the bike.
EAR PLUGS
The Yamaha has a distinct raspy, cracking sound to the motor out on the track. These bikes run what’s called a ‘Slater Skins intake Cap’ which is cut out holes where most bikes have their petrol tank. This opens up air flow and adds to the power output.
What I can certainly tell you is that it adds dramatically to the decibel reading going straight into your helmet while riding. I actually asked Trav (WBR team manager) if the riders use ear plugs and the answer was no. I would definitely consider ear plugs if I had to ride this bike day in day out.
SUMMARY
The number 27 WBR Bulk Nutrients Yamaha YZ250F is a purpose built race bike that is not meant for everyone. It is exceptionally fast when kept in the right part of the power and is capable of holeshotting against any field. The proof is in the pudding when you look at the results from the team’s gun riders so far this year with Koby Hantis, Kayd Kingsford, Kobe Drew and Seth Burchell
2024 WBR BULK NUTRIENTS YZ250F SPECS
Chassis/controls –
Ground clearance 350mm
Weight full fluids 103kg
Caster angle 26.9
EZE clamps
Pro Taper handlebars SX bend
Zeta top clamp
Zeta aluminium bolt kit
Cycra plastics
MX Ink Graphics
Strike seat foam and seat covers
Zeta pivot perch and front brake lever
Zeta rotator shifter
Brakes –
OEM calipers with 74 coatings
270mm front and 240mm rear braking rotors
OEM pads
Yamalube brake fluid
Suspension –
Ohlin’s RX48 fork and Ohlin’s TTX shock
Seth running 45N fork springs and 50N rear spring
Wheels –
EZE wheel set
Dunlop MX34 tyres
Dunlop Mousse rear and heavy duty tube front
Drive Train –
JT sprockets
DID ERT3 chain 114 links, 65mm slack
Gearing 50 rear and 13 front depending condition and rider
Internal gear ratio –
1st – 2.143 (30/14), 2nd – 1.750 (28/16), 3rd – 1.444 (26/18), 4th – 1.222 (22/18), 5th – 1.042 (25/24)
Engine –
Bore and stroke – 77.0 x 53.6 mm,
Comp ratio 14.2:1,
VP Roo 100 fuel,
Yamalube RS4GP oil,
GYTR piston, in house cylinder head work,
74 works REM finish transmission and crank,
GYTR clutch,
GYTR engine covers,
Intake mods to enhance bottom end power and Slater skins intake cap,
Pro Circuit Ti6 Pro
Electrical –
GET SX1 ECU with 2nd injector, second start button under tank
Some of the finer bits –
Zeta holeshot button, Zeta brake master cylinder caps, Pro Taper grips, Zeta rear brake clevis, Unifilter o2 Rush air filters, Zeta case saver, Zeta axle blocks.
WORDS | LEE HOGAN
PHOTOS | JEFF CROW