We’ve tested the Yamaha YZ450F repeatedly since the new version was introduced in 2010 and reemerged in 2011 unchanged. It constantly impresses with a slew of go-fast characteristics that have made it popular with regular Joes and has it currently fighting for a Supercross title in the hands of James Stewart. But what about the rest of the dirt racing community, those sporting enthusiasts who don’t spend their time on a manicured motocross track? Yamaha offers the WR lineup for trail riders and it’s a fantastic machine, but not exactly what the racing community has been seeking. Top programs like the Am-Pro Yamaha squad have tried both models and settled on the new YZ-F. We picked up an invite from Yamaha to try out a nearly stock YZ450F at the Steele Creek GNCC in North Carolina. Not knowing quite what to expect from a burly open-class MX bike in a two-hour cross-country setting, we packed our bags and headed East.
With the bike prepped by Yamaha’s factory GNCC team, there was nothing left to do but sign up for two hours of mud and suffering.
We met Randy Hawkins and the Am-Pro Yamaha GNCC team in their Travelers Rest, South Carolina race shop for our first look at the bike. The factory mechanics were just finishing a few minor touches to prep the bike for a weekend of abuse. Considering they usually have to prepare a machine for the likes of Paul Whibley and Thad DuVall, it wasn’t much sweat off their brow, but we’re thankful nonetheless. Glancing around the bike revealed most of the changes including an oversized IMS fuel tank, Cycra flag-style hand guards, Dunlop MX31 soft-terrain tires front and rear, Tag grips, GYTR/FMF exhaust muffler and Braking oversized front brake rotor. We had to pester the mechanics to find out that a flywheel weight had been installed and later opted to slap on a G2 Ergonomics throttle cam. With everything taken care of we just had to worry about drinking enough fluids and getting a few basics like handlebar and levers set up to our liking. Using stock suspension, we deferred to Whibley’s mechanic, Scott Brooker for settings. He clicked them out to 12 on the fork compression and rebound, 12 on the shock rebound, one turn on the high-speed compression and eight clicks on the low-speed compression. We also made the decision to raise the fork a couple millimeters – the width of a standard screwdriver tip – for slightly quicker steering.
There wasn’t much to do except head for North Carolina where we lined up on the morning two-hour race after a night of hard rain and cold temps that persisted all day. Paul Whibley offered some advice for the dead-engine start (he gives several racing tips in our Paul Whibley GNCC Interview 2011 or see sidebar). Out of 10 practice kicks we nailed eight on the first stroke so it seemed like a done deal. Just follow the procedure, long-stroke kick, no throttle and then power off down the grass straightaway for a holeshot. Of course, that’s never the case once the green flag waves and I stopped counting at four kicks. Things went from bad to worse as I stalled twice and crashed four times in the first 1.5 laps. Suffice it to say that I labored through the opening laps until reaching the gas stop when I could finally regroup and start to enjoy the performance of the YZ-F.
There’s certainly no concern with a lack of power. Ramping up the motor for a two-hour torture session wasn’t exactly necessary for an assault on the amateur class. But adding torque plays right into the strengths of the YZ450 which has gobs of low-end grunt that makes it one of the more aggressive machines to pilot when traction is available. For that matter, it’s just as tough to hold onto in the mud, but the nice thing about a robust bottom end is that it can carry a gear high and chug along in a tamer manner. This technique helps keep engine revs low, minimizes wheelspin and helps carry smooth momentum in the slippery terrain. I didn’t really start taking advantage of this until later in the race when I actually found some semblance of a rhythm. At that point it was clear that with the FMF PowerCore 4 muffler ($300) there was enough muscle from the reversed cylinder to be careless with gear selection. A quick stab at the clutch would get the bike up into the rev range and there wasn’t anything on the course that came remotely close to challenging the Yammie for power. This exhaust is a closed-course application, which is fine for GNCC, but it has the added benefit of a spark arrestor. That would come in handy later in the GNCC season once things start drying out.
Plowing through mud and lugging up slimy hills was much easier with the additional flywheel weight. This was definitely our favorite upgrade.
Adding a flywheel weight was the single best modification on our short list of upgrades. Having experience with nothing less than nine ounces, I was skeptical about the 4.4-ounce weight ($225), but the difference was huge and immediately noticeable. Tractoring up the hills was much easier thanks to the extra gyroscopic action. Rather than stalling under sloppy clutchwork – which happened constantly thanks to collapsed forearms – the YZ plowed along unfazed. One of our early stalls was due to running into the back of another rider and the other a complete meltdown in basic motor skills. This was by far the most impressive addition to the stock YZ and it proved that it doesn’t take a lot of extra weight to make a big difference. We’d be more than willing to use this heavier flywheel even in motocross settings where the easier power and more forgiving nature would have us riding harder for longer.
G2 Ergonomics Throttle Cam System
Changing a bike’s power characteristics can be accomplished in a number of ways. Standard means like a new exhaust pipe or fuel and timing mapping take big bucks, special hardware and extra time. G2 Ergonomics avoids the hassle by going directly to the one thing that a rider uses to control the engine – the throttle. Using an aluminum throttle tube ($50), G2 offers varying throttle cams ($25 each) which feature different profiles. A stock cam is perfectly round, but the G2 units are lobe-shaped and make for a non-linear pull on the throttle cable.
We used the #400 cam which is roughly 20% smaller than stock for the initial pull. Basically it doesn’t yank the throttle cable as hard for the first 1/2 throttle rotation. After that it reverts to the stock profile and the top-end pulls just as hard as usual. There are multiple cams available depending on the desired effect – it can even go the complete opposite with as much as 20% larger than stock creating faster response (would be great for 250F machines). All of the cams are machined from 6061 aluminum, use self-lubricating Delrin bushings and feel incredibly smooth.
Top: IMS does a great job of keeping the YZ thin while offering 2.4 gallons of fuel. Above: Braking Batfly 270mm oversized rotor.
IMS 2.4-Gallon Fuel Tank
Fuel injection helps make modern 4-strokes pretty efficient, and the Yamaha’s 1.63-gallon stock tank probably would have been fine for my half-throttle pace. Guys and gals who are harder on the gas need extra fuel to avoid getting stranded and oversized tanks are standard procedure for GNCC racing. We utilized a 2.4-gallon IMS tank with screw-on cap ($275). I definitely wasn’t missing the dry break during our sole pit stop as I relished every second of rest time. Riding with the bigger fuel cell is very simple. Tanks for some bike models get slightly bulky due to the way it has to form around the chassis and engine. In the Yamaha’s case, IMS uses a very tall neck and any extra width is unnoticeable. The bike is very slim and the tall neck is far enough forward that it doesn’t hamper rider movement. Any discipline of off-road racing/riding will benefit from a larger tank like this.
Braking Batfly 270mm Oversized Front Rotor Kit
I didn’t expect the oversized brake to really be a major asset. The stock brakes have always suited me for anything my skill level is capable of, but I was soon spouting praise for the bigger setup. The end of the handlebar landed directly on my right index finger in my first tip-over. Combined with the cold weather it rendered the digit mostly useless for the majority of the race. That, of course, is the finger that constantly covers the brake lever, and I found that the improved strength provided by the rotor made up for virtually no strength in the finger to squeeze with. The Braking setup completely saved me and I was able to actually get some feel out of the brake. Obviously there was no issue with overheating. This is definitely something that can be useful for riders of all skills and the Batfly design ($324) looks great with its black grooves.
Facing mud, brush and trees, hand protection is a given for racing. Cycra makes a slew of different combinations to accommodate different levels of coverage, mobility and comfort. The Stealth DX ($50) is a flag-style guard that mounts using 6061 T-6 aluminum mounting bars with plastic shields and flexible rubber edges. The extra rubber adds 20% more coverage than standard Stealth guards. One of the cool things about the DX is that its bracket design offers an upper and lower mounting position. Because it does not use a complete wrap-around bar, this is a popular option with moto-minded riders or those afraid of getting their hands caught in a crash. It also saves weight and the mount brackets will rotate to avoid breaking in a hard impact. We put that to the test right away with a crash that pushed the right guard up high. Personally I prefer a full wrap-around and reminded myself of that by punching a tree so hard it wrapped the clutch lever around my fingers. The DX guard simply flexed and allowed that to happen. While I appreciated the mud protection during the horrible start, it wasn’t beefy enough as I ping-ponged around the course.
For extra control, Yamaha installed a set of medium compound slim grips with half-waffle design ($10). These performed well, even after being dropped in the mud. The slim diameter didn’t seem to make a huge difference for me, but the endcaps didn’t rip when I dropped the bike and I didn’t blister.
The Dunlop MX31 tires were charged with finding traction in deep mud, wet rocks, slimy roots and even slippery wooden bridges. Overall they were impressive.
Dunlop MX31 Front Tire and Rear Tire
This was definite the type of terrain for Dunlop’s MX31 soft-terrain tires. We were thrilled to have them on the 21-inch front and 19-inch rear wheels. There were a few times that the front was completely packed up and the clay soil made it difficult to clear the knobs, but those were only when we made a mistake and were forced to come to a stop. Otherwise they performed very well. The rear in particular was very satisfactory. The front had a very challenging assignment and once we picked up the speed a bit they stayed clean and fought for traction. Early in the race there was only one or two lines to choose from, but as the course developed and got worked in, line selection became more critical and the Dunlops were solid when trying to switch direction, even when we weren’t precise with our wheel placement (basically all the time).
While my personal performance was sub-par and definitely not indicative of the machine’s performance, I really started enjoying what the YZ had to offer in the last half of the race. On a more successful note, Yamaha’s Tim Olson was on an identical machine (minus the G2 throttle) and he claimed his first-ever GNCC class victory. He put in a hard-fought ride and the YZ450F proved capable of winning against determined amateur competition. Further delving into the off-road potential would only make this bike better. Just imagine what it could be with full suspension mods, tailored fuel injection maps and small details all around. That’s what the Am-Pro Yamaha squad does and the big Yammie has stood atop podiums at the highest level of GNCC racing. All told our basic attempt was something that any YZ-F owner could accomplish with minimal funds and basic mechanical skill. There’s a reason hard-core off-road racers choose motocross bikes as a base platform. This project goes to show that even normal guys like us can enjoy motocross and grueling off-road on the same machine.