YZ250FX LONG-TERM TEST

It should have come a long time ago. The Yamaha YZ250FX is a bike that makes sense, but for some reason the idea scares the wits out of big Japanese companies. The FX is an off-road bike for closed-course competition, according to the EPA and the California Air Resources Board. Yes, that’s a contradiction in terms, but it’s almost meaningless in the real world. The bike can’t get a green sticker in California, but you can still race it out west, and that’s exactly what I’ve been doing since the start of the year. The AMA District 37 Big 6 GP series doesn’t require green stickers and actually has a class that’s perfect for the bike. They divide the age-defined classes into Lightweight and Heavyweight, meaning I don’t have to keep up with nut cases like Paul Krause and his KTM 450 in the Magnum Expert Heavyweights. There are plenty of nut cases in the Lightweights too. Most of them are on 250 two-strokes, which race against 250 four-strokes now.
WHAT I’VE LEARNED
Racing the FX has been a learning experience. It is exactly what Yamaha says it is: a YZ250F motocrosser set up for off-road, with electric start and a six-speed. There’s some confusion surrounding the WR250F, which is almost the same bike, but with emission and noise restrictions. That’s the green-sticker version, and it has a few other features, like a headlight, a radiator fan, a skid plate and softer suspension. The price is only $100 more, so it’s really the better bargain of the two, but you have to install the GYTR competition kit (black box and throttle stop) to unplug it. More on that later.
Right out of the box, the FX is awesome for the Big 6 races. It has two advantages over most of the two-strokes that fill up the Lightweight class. The biggest is the six-speed. These races are all set up by desert clubs, which means there’s always going to be a section where you’re going way, way faster than you want to go. Sometimes it’s paved. There’s nothing better than sitting upright and re-passing the guy who just worked his butt off to get around you in knee-deep whoops. Good times. The bike is actually over-geared in sixth. It can’t pull the gear unless you have a long, long straight. But, first gear is still plenty low for tight stuff, so you never have to change gearing for any race.
The second strong point for the FX is suspension. It’s perfect, at least for me and these races. I’m a 190-pound oldish guy and wouldn’t dream of sending it away to a suspension shop. It is, however, a Yamaha, and that means the fork seals will leak after a few rides. Replace them the easy way without changing the oil level, if possible. Click here for a story showing how to do this. The YZ is a great machine in most other ways too. I love the electric starter. The bike weighs 17 pounds more than the motocross bike, which is mostly the battery and starter. You can feel it, but it’s not that big a deal. I could save 5 pounds with a lithium battery, but I decided not to go down that road until the hottest part of the summer. Earlier in the year, the lead-acid battery was great for those early-morning cold-weather starts.
WORK IN PROGRESS
I need to admit, I feel like a bit of a traitor. I’m racing against two-stroke guys who look at me like I’m the enemy. I’ve always defended two-stroke honor for good reason. Two-strokes really are lighter and more powerful. The FX makes it a little tougher, because of the aforementioned weight and the fact that it’s not quite as powerful as even a YZ250F motocrosser. There are two things that hold it back. The first is the muffler. The FX comes with a Euro-spec YZ pipe, which is a little more restrictive. That’s easy to fix. I tried a number of pipes, but settled on a Pro Circuit T4 full system. Still, the bike didn’t quite run like the motocross version. The fuel mapping and spark advance are clearly different.
My first attempt to address this was a disaster. I installed the black box from the motocross bike. That didn’t work. The electric start was disabled, and eventually the battery was damaged. It turned out that the FX has a circuit that turns off the EFI system after a few minutes of inactivity. With the YZ box, the whole system hummed all night, eventually damaging the battery to the point that the bike couldn’t power the EFI, even after being kick-started. The stock black box can be remapped fairly easily on the FX if you have the GYTR Power Tuner. On the WR, the engine controller is locked, which is why you need the $106.95 competition kit. The black box in the kit is the same as the FX’s. The Power Tuner sells for $290, which is still cheaper than any other EFI tuning system.
You can adjust the ignition advance and alter the fuel mixture within certain limits. There’s no magic button that makes the bike into a YZ, though. You just have to play around with the settings. In general, you get the most result from advancing the ignition. No matter what I tried, I never quite made it feel like a YZ. There are differences in crank weight, certainly, but there are probably undisclosed differences too. I decided not to go further down the path in search of more power. I like the bike too much to mess it up.
STEP BY STEP
After each race, the bike was altered in some way or another, based on “dumb lessons learned.” The first GP was at Adelanto, California, in the high desert. It gets really cold in January there. Many parts of the track had been watered the night before, and long sections turned into sheet ice by morning. That wasn’t the real problem, though. It was my hands. They were so frozen that I had to stop on the first lap to warm them on the pipe. Thus, the first change was Hot Grips from A’ME. As it turned out, I never needed them so badly again, but I’ll be ready next year. At that race I also learned that I’m too uncoordinated to manage the Big 6 start, where you wait for the green flag with your left and on the right grip. Instead of grabbing the clutch, I grabbed the handguard. The next change was a set of Sunline Moto Ray handguards. They pivot down, out of the way for the start, then can be snapped back into place on the fly. Of course, I usually forget to bang it back up and spend the entire race with my handguard protecting my knee. So it goes.
After the next race at Taft, I realized that the clutch lever is way too easy to pull. It turns out that the springs are lighter than those on the YZ, and that translates to a shorter clutch-plate life expectancy. I upgraded to an entire Hinson clutch with stiffer springs. At Glen Helen I realized that the bike needed more front brake. The problem with having a bike that has a higher top speed than almost anything else in the class is that you tend to hold it on a little too long on the straights. Then things get panicky in a hurry. The Yamaha front brake needs more strength. I settled on a Galfer 270mm rotor and pads. That was all I needed.
Then came the biggest reality check of all. The GP at 29 Palms is slightly faster than the Daytona tri-oval. This is a real desert racer’s type of GP, and it seems that my mental processing speed is a few megahertz too slow. It wasn’t the best course for a 250F, either. That was when I installed the GPR damper. If I’m going to go that fast for that long, I need every bit of stability I can get.
NEXT CHAPTER
I’m not through yet. The bike is sure to change more by the end of the season. At this rate, it will be absolutely perfect shortly after the last checkered flag falls. It should be coming into its prime when most bikes are worn out. The YZ250F has a reputation for being the most reliable 250 four-stroke on the market. After a season of racing, it will be due for a set of rings, a timing chain and a valve adjustment.
Chances are, though, I’ll be much more worn out.

—Ron Lawson