Putting A Larger Aftermarket YZ-F Tank On An FX

AmPro Yamaha's Corey MacDonald and Lucas Statom show us how

This article was originally featured in the August 2017 print edition of Dirt Rider

The Yamaha FX line is built specifically for the off-road market, but due to the need for a battery to power a starter and a cooling fan, the aftermarket FX tanks are smaller than the aftermarket YZ-F models by nearly half a gallon. That capacity deficit can mean the difference in an extra lap at a GNCC race—or more time on the trail before needing to return to the truck.

Here’s a look at the “FX oversized” tank on this Yamaha YZ450FX. The FX has a 4-inch-wide battery under the seat to power the starter and fan, so there is less room for the fuel tank than there is on a YZ-F.Shan Moore

The mechanics at AmPro Yamaha—Corey MacDonald and Lucas Statom—figured out how to solve the problem by using a smaller battery. The cool part is they managed to do it without eliminating anything on the bike, though on more recent adaptations MacDonald has trimmed down the wiring loom considerably. For instance, since the team doesn’t use the cooling fan, the fan relay system with fuses and relevant wiring is removed from the wiring loom. MacDonald even found a way to eliminate the tip-over switch on their racebikes, thus eliminating even more wiring.

You can see the “YZ-F oversized” tank, mounted here on an FX, has more room for fuel down low and rearward, which is an ideal place for extra fuel.Shan Moore

According to Lucas, the big secret to making everything fit is to replace the rather large stock battery (4 inches thick) with a much thinner (1.5 inches) Antigravity SC-1 battery and then carving out a notch underneath the seat to accommodate the new battery. Lucas next puts a metal plate in the notched-out area so the rider can’t feel it and then coats it all with Yamabond. In addition to the fuel-capacity gain, there is a huge weight savings and an increase in cranking amps. The YZ-F aftermarket fuel tank is made by IMS, and the cool part is that all the added fuel is down low and rearward.

There’s considerable difference between the two batteries. The stock battery, which is much wider and heavier, is on the right, while the thinner, lighter Antigravity SC-1 battery is in the bike.Shan Moore
Here’s a look at the new battery mounted up on the FX. You can see that it fits a little bit above the frame so a section of the seat has to be hollowed out.Shan Moore
Lucas Statom holds the seat that he has hollowed out and sealed with Yamabond. There is a metal plate in the bottom of the notch so the rider doesn’t feel the battery.Shan Moore
The stock wiring harness is at the top with the trimmed-down version at the bottom—big difference. Corey has eliminated the wiring for the lights, the cooling fan relay system with fuses and relevant wiring, and the tip-over relay. But don’t try this at home because all these systems have to be grounded and blocked off correctly so they are not a danger.Shan Moore

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