Creating Goliath: 2015 CRF480R Big Bore Build

The horsepower that motocross bikes put out these days is impressive to say the least. Back in 1993, the 500cc motocross class was killed off because people thought the 500cc two-strokes were too fast and hard to ride (not to mention some political reasons as well). The Honda CR500R was the king of power back then, making around 55 horsepower! Fast forward to today when the industry has changed to four-strokes and the 450 class reigns supreme. The new Yamaha YZ450F is today’s king of power pumping out over 52 horsepower, nearing the 55 horsepower mark the CR500R had previously set. That is a lot of power! Although the new four-stroke power is easier to manage, it is still more power than most riders can actually use effectively. However, we all seem to want more. The later model Honda comes in shy of 50 horsepower, lacking in comparison to other dirt bikes in the 450 class. While the Honda CRF450R does offer an easy ride with calm, smooth and consistent power throughout the powerband, it leaves something to be desired for riders who prefer an aggressive punch when they pull on the throttle.

In my latest build for Dirt Bike Magazine, I tried to break out of the stereotype that has been attached to the recent CRF450Rs. We took a brand new 2015 Honda CRF450R and went all out to turn it into a monster of a bike. The finished product? Meet Goliath – a 480cc mammoth of a bike that silences all whispers of inferior power.

The Transformation

The heart of the build was the installation of a Cylinder Works Big Bore Kit that added an extra three cm to the cylinder and turned the bike into a 480cc powerhouse instead of the more timid 450cc it started out as. The big bore kit was a great value for the significant power increase that we got and is an easy way to see just how much power this machine can use. Just think, if you need a new piston anyway, you are already halfway to justifying a big bore kit. The whole kit comes ready to bolt right on to your bike so you don’t have to send out the cylinder to be re-bored and end up waiting on the shop to get it back to you.

Since we drastically changed the bottom-end, we decided to add a Stage II Hot Cams camshaft to help offset the big bore and let the motor rev out a little more in the mid to top-end. To ensure precision performance of this revamped engine, we added a Hinson clutch kit and billetproof clutch cover to go with it.

Although the stock fuel mapping works alright with the bike, a remapped ECU can work even better. We added a Vortex ECU so that the engine would perform with optimal power and be mapped perfectly with rocket performance.

An FMF Megabomb Header and full Factory 4.1 Dual System really opened up the exhaust on this bike and turned it into a beast.

No build is complete without sweet accessories and extra additions that not only customize the performance of your bike but make it look great too. Just about every cool accessory we could think to add was available through Tusk and Works Connection: a full set of Tusk Impact wheels with red hubs, rotors, brake lines, a clutch perch assembly, axle blocks, engine plugs, reservoir caps, an hour meter, and foot pegs are just a few of the extras added to this motorcycle. (Take a look at our parts section if you ever need a few ideas on what’s available to add to your bike.)

Dunlop MX32 tires are the standard for intermediate terrain and work in a wide range of motocross terrain, so we figured they would be the perfect fit for this bike.

To give our Goliath bike a full custom trick look and feel, we added a full plastic kit in all red and dressed it up with custom graphics from Attack Graphics.

The Aftereffect

So what’s it like to ride this beast? Let’s just say that calling it Goliath is no understatement. For many out there (myself included), this bike can be too much power – a handful to ride for sure. Adding the big bore to this CRF450R certainly made up for the mild and smooth power from the stock, and turned it into a beast that hits hard from the bottom to the top. This big bore picked up about 4HP in the meat of the midrange and much more torque (grunt) than stock. The stage 2 cam helps keep it revving out on top so it doesn’t feel like a lazy motor. This bike is only for those that are not afraid of some serious bark and bite, and are willing to hang on to all she has to offer because this CRF480R doesn’t let up. It is best suited for those racing much larger, deeper type tracks that can really utilize all that Goliath has to throw at the rear wheel.

Just about all of the modifications we did can be done on all of the 2009-2015 CRF450R models. Although this whole build was mostly bolt-on parts which saves on overall cost, doing all of these mods at once would be pretty difficult for a lot of us due to budget constraints. But if you like what you see, use the Goliath build to see which parts and mods might work for your CRF450R and add them as you can! Check out the April 2015 issue of Dirt Bike Magazine to see what their test riders had to say about this CRF480R transformation.

Products Used

By Jay Clark