MXA RACE TEST: THE REAL TEST OF THE 2024 YAMAHA YZ250F

Q: FIRST AND FOREMOST, IS THE 2024 YAMAHA YZ250F BETTER THAN THE 2023 MODEL?

A: It’s no secret that Yamaha makes a potent 250-class weapon. It has been the most dominant 250 four-stroke since 2014, and the Star Racing Yamaha team has won eight regional Supercross titles and five 250 National titles on this bike. In the pro ranks, the Star Yamaha engine has set the standard in the 250 class for a few years now; however, in stock form, Yamaha has fallen behind KTM, Husqvarna, GasGas and Kawasaki on horsepower numbers. The difference is the tuneability of the YZ250F engine. The downdraft intake and backward engine have their quirks, but they offer a great platform for engine builders to create maximum midrange power. 

When the 2024 news came out, we learned that Yamaha only made minor updates to the YZ250F engine, with most of the changes being focused on the chassis. Overall, the new bike is better, but it takes some effort to find harmony with the new chassis and engine updates. 

Q: WHAT’S NEW ON THE 2024 YAMAHA YZ250F CHASSIS?

A: To state it simply, the YZ250F gained all the exact same parts that the Yamaha YZ450F gained last year, only the engine, engine mounts, intake boot, ECU settings and suspension settings are different. Essentially, all the other parts will cross over between the YZ250F and YZ450F. The goal for the new chassis was to resolve all of MXA’s complaints by making a bike that was slimmer, lighter, nimbler and less compact—and they did it! Here’s a list of the major chassis updates. 

(1) Frame. The aluminum bilateral beam frame is made from 10 pieces. The tank rail to head-pipe joint has been lowered 15mm. The tension pipe was lowered 15mm at the down tube with increased rigidity at the down tube, swingarm pivot and footpeg cross-member. The engine mounts were lowered with a material change from 8mm-thick aluminum to 5mm-thick stepped-steel plates. Two 8x135mm through bolts make the engine more of a frame stress member. 

(2) Subframe. The lower rail thickness has been reduced from 1.8 to 1.5mm, and the starter battery and tray position have been adjusted. 

(3) Suspension. Thankfully, the great Kayaba SSS forks remain, but the settings on both the fork and shock have been updated to match the new chassis. The forks also gained hand-adjustable compression clickers. 

(4) Bodywork. The all-new plastics have a unique, modern style. They are 2 inches thinner at the widest point of the shrouds. 

(5) Refinements. The rear axle’s inner diameter has been changed from 20 to 20.5mm to increase traction, and the rear brake hose is softer to offer a better feel at the pedal. 

(6) Weight savings. The footpeg brackets, airbox, subframe, wiring harness, battery tray, chain guide, throttle cables, fuel pump, rear axle and plastics all help the YZ250F save an impressive 3 pounds on the scales. It now weighs the same as the KTM at 224 pounds.

(7) Rider triangle. The cockpit is much better now. The seat is 15mm flatter and 5mm taller. The footpegs are 5mm lower and 5mm further back, and the handlebar position comes in the rear holes of the triple clamps, but those are adjustable with four different bar mounting positions. 

Q: WHAT’S NEW IN THE 2024 YAMAHA YZ250F ENGINE?

A: This engine is very similar to last year’s with a few adjustments. The 2023 YZ250F and earlier model cam chains had big durability issues whenever riders would modify their engines. We never had issues on our MXA test bikes, but we also didn’t modify them like most aspiring pro racers. The 2024 cam chain was updated for durability, and the intake tract was changed to fit the new frame and plastics. Here’s a list of the engine updates:

(1) Cam chain. Everything about the cam chain is bigger and stronger. The cam chain is now 1.25mm wider, (going from 8.25 to 10.2mm) with a three-by-two chain configuration instead of the four-by-three chain it had before. The sprocket width has been increased by 1.5mm at the cams and crank, and the cam chain tensioner and dampers have been made wider to match the chain.

(2) Intake. The air intake matches that of the YZ450F, with the only difference being a longer rubber intake boot (to span the gap) from the throttle body to the new frame. The air ducts on the shrouds have been removed. The airbox and top cover have a new shape with increased volume. The 3D dome-shaped air filter replaces the flat piece-of-toast-style filter from last year. The filter has 56 percent more surface area, and the clean side of the air boot has 30 percent more volume. The airbox is also in a 15mm lower position now, working with the flatter seat profile. 

(3) ECU. The hardware of the electrical control unit is simplified, and it matches the YZ450F, with unique settings for the YZ250F. Of course, it can connect to the updated Yamaha Power Tuner app for adjusting maps, monitoring engine hours and more. 

Q: HOW IS THE 2024 YAMAHA YZ250F ENGINE?

A: It’s interesting. The layout is identical to 2023, with the only updates being to the intake, cam chain and ECU mapping. Right away, our testers noticed a lag in power on the bottom end. Since the YZ250F is best known for its impressive “get up and go” power off the crack of the throttle, we were unimpressed by the 2024 YZ250F’s throttle response; however, once you get into the revs, it shines. The midrange is slightly stronger and more exciting than before, but the engine revs out quickly, requiring quick action out of your left boot.

As soon as our testers opened it up for the first time, they rode back to the pits for earplugs. Yes, it’s even louder than before with the bigger airbox mounted in front of the seat. 

Originally, we were surprised by the lag in power off the bottom and blamed it on the all-new cam chain system being stronger, heavier, and wider; however, Pro Circuit engine guru Mitch Payton enlightened us, explaining that wasn’t the case. Based on prior experience with heavier cam chains and larger airboxes, Mitch mentioned that the larger airbox was the most likely culprit. It’s difficult for a smaller engine to suck air through a larger 450 intake. Yamaha explained to us that they had issues with the YZ450F airbox on the YZ250F, and they had to change from a plastic to a rubber boot, which benefited power, thanks to the pulsing of the rubber intake boot walls. However, the air inside still doesn’t have the same velocity it did in 2023 and prior. 

Combustion engines use a “suck, squeeze, bang, blow” method for creating power. They suck a mixture of fuel and air into the combustion chamber and squeeze it together (compression), then it burns/explodes with a bang and finally blows out the exhaust. If you slow down the air speed as it travels into the engine, you’ll hinder throttle response and low-end power. Of course, aftermarket tuners will have quick fixes for this. (Twisted Development already has a solution. Stay tuned for a future test.) 

Don’t let us fool you, though; the engine isn’t all bad. Most skilled riders who know how to manage a 250 four-stroke and ride it in the meat of the power will have zero complaints with this engine, but beginners, novices, vets and guys who don’t like to clutch it will notice the difference. Riding the 2023 and 2024 YZ250Fs back to back, you’ll find the new engine is slightly stronger on top, but it’s hard to get there because the improvement is so high in the rpm that once you find it, you need to shift again or hit the brakes for the next turn. We lowered the 50-tooth rear sprocket to a 49, and that helped significantly because it lengthened each gear; however, it didn’t fix the lull on the initial throttle response.  

Q: HOW DOES THE 2024 YAMAHA YZ250F RUN ON THE DYNO?

A: The new YZ250F dyno numbers aren’t pretty. It’s slower than the 2023 YZ250F at the initial snap of the throttle. It matches last year’s bike from 6,200 to 6,800 rpm, then it drops below it by almost 1 horsepower until 8,400 rpm where it matches the 2023 model again. It dips below one more time before eventually passing the 2023 bike at 10,200 rpm, and it stays above last year’s bike until it peaks at 42.58 horsepower at 12,700 rpm. The 2023 model peaks at 42.11 horsepower. Basically, the 2023 engine runs a smooth curve on the horsepower and torque charts, while the 2024 engine has multiple dips in it before it finishes strong. 

Of course, you have to take the dyno numbers with a grain of salt. They don’t win races; it’s the overall package and how the power is put to the ground that counts. But, in this case, the dyno numbers exactly matched what our test riders felt on the track. 

Q: HOW DOES THE 2024 YAMAHA YZ250F HANDLE?

A: We’ve learned a lot about this chassis since we’ve lived with it for a year already on the 2023 Yamaha YZ450F. That bike won our 2023 MXA 450 shootout, but it’s not without its flaws. Yes, it’s much lighter than before. It’s much skinner than before, and it’s much nimbler than before, but Yamaha went a little too far on the nimble scale, making the front end twitchy on rough and fast straights. After one year, we expected Yamaha and Kayaba to have worked out the kinks in time for the release of the YZ250F. Plus, with the 250F engine being smaller, lighter and having much less rotating mass, it’s always easier to make it handle better than the heavier and faster YZ450F. 

Unfortunately, many of the same issues we faced on the YZ450F have transferred over to the smaller bike. The forks feel soft, and they dive into corners. The heavier deceleration feel doesn’t help, which is another complaint that we attribute to the new intake system. The front end is also very busy, making it harder to be smooth in turns. Through testing, we were able to resolve most of our complaints with clickers, but it certainly wasn’t as easy to feel comfortable as it was on the stock 2023 YZ250F. 

Q: HOW IS THE NEW YAMAHA POWER TUNER APP?

A: We’ve been using the updated app on the YZ450F for the last year, and we really appreciate how easy it is to use. With a simple slide bar, you can make the bike more or less aggressive. You can also customize the amount of traction control you want and even customize the launch control you want for starts. If you prefer to see the charts and numbers, you can still access that as well. Your smartphone connects to the bike via Wi-Fi, and it’s relatively easy to do. The app also allows you to log notes to keep your settings in one place and it gives recommendations for suspension changes based on how you feel on the track. It’s also great for maintenance and logging engine hours, and the real-time dashboard shows your throttle position, rpm, speed and more. 

Q: WHAT DID WE HATE?

A: The hate list:

(1) Seat. The seat is hard and awkwardly shaped in a way that is not comfortable to sit on for any extended period. 

(2) Air filter. The stock design still allows dirt to get into the engine. We replaced it with Twin Air’s power flow kit. Twin Air designed a new air filter that addresses the problem with two round grommets, front and rear, that slip over the posts to hold the filter securely in place. Additionally, the Twin Air Power Flow kit comes with an aluminum cage (minus the backfire screen), and a small aluminum L-bracket to hold the filter/cage securely in place. Also, if you lean the bike on its side to change the air filter, there is less chance that dirt will fall into the downdraft intake. If some dirt does slip past, grab a shop vac while the dirt it still sitting on the throttle body’s butterfly and suck it out. 

(3) Throttle response. We’re sad that the Yamaha lost the low-end grunt this bike was best known for. 

(4) Clutch. We’d prefer a hydraulic clutch. 

 

Q: WHAT DID WE LIKE?

A: The like list:

(1) Crossover. It’s always nice when the 250 and 450 share all the same parts, making availability better.

(2) Power. The YZ250F is an exciting bike to ride. It’s not the fastest when you compare it to other 250s, but the low-to-midrange torque makes you feel like it is. 

(3) Bodywork. We appreciate the lengths Yamaha went to to make the bike slimmer. 

(4) Clickers. We like that the Kayaba forks come with hand-adjustable clickers, but they’re difficult to use. Works Connection makes a replacement that’s easier to turn and looks factory. 

(5) Bolts. Yamaha reduced the number of bolts needed to install the rear fender, which saved a lot of time. 

(6) Access. We appreciate how easy it is to remove the fuel tank and take the rear shock off without taking the subframe apart. 

(7) Wheels. Yamaha’s wheels are ultra-durable. 

(8) Wi-Fi. The new Power Tuner Wi-Fi app is much easier to use. Thanks, Yamaha.  

Q: WHAT DO WE REALLY THINK?

A: The new Yamaha YZ250F certainly has some bugs to work out, but that’s what keeps the aftermarket engine and suspension tuners in business, right? The process of building a new bike isn’t easy, especially when you have to share parts from a 450 with a 250. Ultimately, we nitpick every bike that comes into our stables because it’s our job to get to the bottom of how each bike performs. We break it down so that our loyal readers can make an educated purchase at the dealership. The new Yamaha YZ250F is lighter and skinnier, has better ergonomics, an easier-to-use Yamaha Power Tuner app, a more durable cam chain, fewer bolts holding the rear fender on, and a strong engine. Yes, the 2024 Yamaha YZ250F chassis will take more effort to get comfortable on, and the engine isn’t as potent off the bottom as it was, but those are issues that can be worked through.