Not everyone wants to “add” parts to their new dirt bikes, which is fine, but for those that must tinker, we put together a “Top 5” must haves that we would recommend. We will be doing these “Top 5” articles with all of the new 450F/250F’s (along with a couple off-road machines) and will be splitting the information up between pulpmx.com and keeferinctesting.com. These mods are recommended, by us, through countless hours of testing. If you don’t find a specific aftermarket company that you prefer in this article, don't fret, email me at kris@keeferinctesting.com and we can talk it out like adults should. Again, we will not push something on you unless we know it works. These mods that are in this article simply work for this specific machine.
1. FMF 4.1 Slip On Muffler
It’s no secret that the 2019 Yamaha 450FX is a great off-road competition bike, but to some it may be a surprise that in stock form it’s not legal to race at the majority of off-road races. The one thing that holds the FX back from being off-road race friendly is the lack of a spark arrestor, which 99% of off-road race organizations require in order to racer on public or even private lands. We opted to go with an FMF slip on muffler which comes with a spark arrestor (in the box, not installed in the muffler) which gave the FX a slightly louder tone and got rid of the slightly raspy stock sounding muffler. With the spark arrestor removed the engine lost a little bottom end roll on power, but gained some over rev. With the spark arrestor insert installed, the muffler mimicked the stock characteristics and gained some mid-range. https://www.fmfracing.com/Product/ProductDetail?CategoryID=584&BikeType=MX%2FOFFROAD&BikeMake=YAMAHA&BikeModel=YZ450FX&BikeYear=2019&ItemID=044443&imaConfig=Single&ParentCategoryID=31&Priority=9
2. Yamaha Power Tuner App
Yamaha is the first manufacturer to offer a phone app to map your motorcycle and it’s awesome! The app is very user friendly and gives you the ability to use Yamaha’s provided apps, as well as being able to make your own. Yamaha provides four maps; Mild Power, MX Power Feeling, High Revving, and Torquey. Two maps are able to load in the bike at one time and I have found myself trail riding with my phone as well as trying other maps when we come to a stop. The maps can be toggled between the handlebar mounted map switch and I have found it very handy depending on the terrain changes. https://www.yamahamotorsports.com/motocross/pages/yamaha-power-tuner-smart-phone-app
3. Firepower Battery
The newest generation Yamahas are very hard to start in gear, and even when in neutral they tend to turn over for longer than desired. I have found that different maps also effect how quickly the bike will fire up. So far, I have killed two batteries in the 450FX just from trail riding and constantly stopping and starting over the course of several hours. Luckily, I was able to bump start the bike both times but after the second dead stock battery I knew it was time for an upgrade. The Firepower battery was slightly lighter than the stock and has yet to leave me stranded. That being said it still doesn’t like to be started in gear. https://www.firepowerparts.com/products/batteries
4. Handguards
I’ve said it before and ill say it again, if a bike is designed to be an off-road bike it should come with handguards. The FX comes with a bitchin skid plate, but they decided not to add handguards on the production bike. Although for the bike’s introduction, Yamaha added GYTR flag handguards, which have been on the bike ever since. It all depends on what type of riding or racing you do, some people swear by flag style mounts, and others will not ride without full wraps, but either way, do yourself a favor and put on some type of hand protection. https://www.shopyamaha.com/product/details/cycra-rebound-hand-shields?b=Motocross+Accessories&d=42|42&ls=yamaha-motor-company&dealernumber=
5. Fork Springs
Although the 2019 FX has much better hold up than the previous generation, the fork still has a slight diving sensation when chopping the throttle or under heavy braking. This can be somewhat fixed with clickers if you aren’t too heavy, but on my 190 pound ass (give me a break my wife is pregnant), stiffer springs will do the trick. Race Tech recommends going from the stock .46 kg/mm to a .50 kg/mm to fix the issue. I have also heard of people putting the springs from the moto bike (.51 kg/mm) and having good results. Either way, a little more hold up goes a long way when your riding gets faster and more aggressive. http://racetech.com/ChooseVehicle.aspx