From Super to Superb
Since Yamaha unveiled the all new YZ250F five years ago, it’s been a quality machine that has a lot of positives to it. Over the last five years, Yamaha has done a lot of fine tuning to chassis, engine and suspension, which made the YZ250F even better. In terms of making changes that make the YZ250F even better, 2019 is the biggest year for changes since its inception in 2014.
Before we get to how it works on the track here are all the changes for 2019, starting with the engine. Yamaha kept the reward slanting engine design (for 2019 the engine is slanted forward 1 degree from the 2018) that already has been in the loop since 2014 and made some changes to make it even better. Starting by adding electric start, Yamaha is the second Japanese manufacturer to have an e-start 250F motocross bike and as spoiled as I sound it’s a welcomed addition. The exhaust port shape was slightly modified so it transitions to the head pipe (which shape has also been changed to accommodate this) better and has increased the flow rate. Also in the head, Yamaha has increased the intake valve lift, and slightly changed the event angle of the exhaust cam. The final changes to the new head are larger lifter buckets and slightly stiffer valve springs. Underneath the head, the piston crown has been increased which has bumped the compression from 13.5:1 to 13.8:1.
The throttle body on the 2019 had changed from Keihin to Mikuni, is 44mm, and has a 12 hole injector. Also different on the throttle body is the cold start (choke) which now has to be pushed in to be activated and is deactivated by fully closing the throttle. Along with the engine changes, and new fuel system, the ECU settings have been updated and the new dual electrode spark plug’s cap now has a finger holder keeping the cap firmly in place. The transmission side of the engine has also received key changes including a heavier duty clutch. What makes the clutch stronger is a larger plate diameter, six clutch springs (one more than last year), and thicker steel plates (which in turn reduced the number of friction plates from 9 to 8). The transmission gears have also been updated and are using a high impact steel.
The new e-start is a compact, sits behind the cylinder, and drives the clutch basket directly. The 1.5lb lithium battery sits under the rear of the seat and has a capacity of 2.4AH and 13.2volts. The amount of power the YZ 250F needs to generate has been reduced because of the addition of the battery which means there is less resistance on the stator/engine.
The frame on the 2019 has been majorly changed to make the bike feel more nimble on the track. The frame rails that go around the gas tank/air box are now straight where last year had more of an S shape. Other parts of the frame have been changed from forged pieces to extrusion aluminum, and the engine mounts have been changed from steel to aluminum. The material at the swing arm mount has been increased front to back and narrowed side to side making the side of the frame flatter at the swing arm mount. The steering head has also been moved forward 6mm to help with stability.
In the past there have been comments about the seat height and width of the YZ 250F. Yamaha had changed that by making the seat slightly flatter, shorter, and narrower than last year’s model. Along with the seat, Yamaha has narrowed up the plastics where the rider’s knees contact the shrouds. The new shrouds have the air ducts integrated into them and the whole top part of the shroud no longer has to be removed to service the air filter. In fact the air filter cover now only needs one Dzus fastener to be removed for access to the air filter which is no longer held in by a screw, instead it’s held in via rotating clips.
Yamaha also tried to lighten the bike up by using thinner, higher strength material for the handlebars and also using lighter rims. To help with stability, they increased the surface area of the wheel collars where they contact the fork lugs, and added more material to the rear collars. The KYB forks use new internals including a new piston, cylinder, mid speed valve, pressure piston, and stiffer spring rates (from 4.6N/mm to 4.7N/mm). The shock reservoir volume has been increased by 30cc, and the coil spring now has less winds, is made of a thinner material (lighter) and the rate has changed from 54N/mm to 56N/mm.
The Yamaha Power Tuner app, in my opinion, is one of the coolest features on this machine. You no longer need a stand-alone device to change the mapping of your fuel injected Yamaha; you can now do it from your smart phone via Yamaha’s app. All you need to do is take your side panel off (only the first time you use the app) and get the bikes serial number, then bump the starter button and connect to the Wi-Fi signal the bike puts out. Once connected you can pair the bike in the app and change mapping, record maintenance, monitor trouble codes and even log your races and track conditions. There is also a handlebar mounted map switch that allows the rider to switch maps on-the-fly. You can load a map from your Yamaha Power Tuner App, directly into your YZ250F and go back and forth between any two maps the rider desires.
Now that all the changes and technical mumbo jumbo is out of the way let’s get to how all that correlates to on-track feeling. Starting with the engine, the 2019 YZ 250F has a more free-revving feeling than the previous model. Yamaha did a lot of work in the engine department on this bike and tried to get added power from mid to top end and they definitely hit the mark. When pulling down a long straight away, or trying to pull a gear a bit longer than the 2018, the 2019 will oblige and pull hard all the way to the rev limiter. This free revving feeling also results in a more playful power characteristic making the engine feel more lively because you aren’t having to short shift to stay in the meat of the power. All that being said, I feel like Yamaha traded a bit of bottom end pulling power in order to gain the top end power. The best way to describe it is the 2018 wasn’t as picky about what gear you needed to be in when exiting corners, you just maybe needed a flick of the clutch (recovery time) and the bottom end power opened up and started pulling. For 2019 you need to be a little more selective about what gear you are exiting the corner in, because if you are a gear high, it will take a bit more clutch work to get the engine into the meat of the pulling power. Although the 2019 slightly lacks bottom end power when compared to the 2018, in my opinion, it’s still ahead of the rest of the 250F field. The last thing in the engine department that needs to be mentioned is the new electric start. I like the fact that there isn't a clutch cancel switch so the starter can be activated at any time. That being said there was a slight hiccup from time to time. When the bike was in gear, it seemed to turn over just fine but struggled to fire at times. If the engine found the compression stroke with the clutch not all the way engaged the starter would stop spinning, and the button wouldn’t work when pushed for 2-3 seconds. After 2-3 seconds it would work as usual when the button was pressed; it almost seemed like an auto reset breaker would pop, then re-set itself and continue working. To combat this I would just try and make sure the bike was in neutral before starting it.
Having the map selector on the bars is definitely a plus, and gives you two separate options that can be changed on the fly. The two maps that were loaded in the bike were stock, and “hard hitting”. Using the Yamaha Power Tuner app is very user friendly and I think one of the cool features is the maintenance recorder. It’s just reassuring to always know when the last time you did things to your bike was and it’ll tell you when it’s time to maintenance certain things again. Yamaha updates their maps that their test riders work on for you to be able to download and try. You can also as well make your own or try one that a buddy has made. We are all a bit scared of electronics, but I have to admit it’s kind of nice to be able to change how the bike runs with the push of a few buttons instead of re-jetting a carburetor. It’s also pretty damn cool that your bike will tell you what’s wrong with it in the app if there is a trouble code (I’ve tried waterboarding a carburetor and never got a straight answer out of it).
The chassis on the 2019 YZ250F is where Yamaha made the biggest improvements. The changes they made to combat some stability issues hit the mark and the bike is night and day better. Not that it was all over the place before, but I definitely feel that the bike tracks better in a straight line and has very little twitchiness to it. Usually when a bike gets more straight line stability it gives up a bit of cornering ability, this isn’t the case with the 2019. The previous model was hard to lean into corners and didn’t like staying leaned over, but the new bike has definitely instilled confidence in my inside rut abilities. Tipping into a corner takes less rider input and staying leaned while in the rut is much easier with the bike not feeling like it wants to stand up. I’m sure some of this comfort is also from the slimmer bodywork on the new model. The slimmer radiator shrouds are a very welcomed change and helped me keep my knees tighter to the bike and my leg tighter to the shroud when it’s up in ruts. This feeling is aided by the 18mm narrower seat at the tank, it’s also lower in the rear which I didn’t notice much, but may be more beneficial to shorter riders.
Rounding out all the positive changes made to the 2019, the suspension has taken a huge step in the right direction. After spending a lot of time on the 2018 I felt that the suspension was too divvy (or had a pitching sensation). The new YZ 250F has a much firmer feeling to the suspension, not stiffer, just firmer. Let me explain myself; when going through rougher sections, the front and rear of the bike are still soaking up the bumps well, they just don’t seem to be transferring energy to the opposite end of the bike which caused the pitching sensation. There is no longer a wallowy feeling, like the suspension is using too much of the stroke, instead it does a better job of staying up in the stroke. On harder landings the bike no longer blows through the stroke, like I said before its firmer not stiffer, it retains a plush feel without giving the rider any harshness.
With all these changes being made to the 2019 YZ 250F it’s going interfering come shootout time. Yamaha has really stepped up their game this year and showed themselves to be at the forefront of technology with the easy to use tuner app. The 2019 is offered in traditional Yamaha blue or white/cyan and has an MSRP of $8,299. Yamaha also offers their “bLU cRU” contingency program for motocross and off-road racers. In addition to the contingency, Yamaha also has free trackside assistance at certain races for any Yamaha racers. If you have any more questions about the 2019 Yamaha YZ250F feel free to reach out to me at Michael@keeferinctesting.com or Kris at kris@keeferinctesting.com. -Michael Allen
