WHAT IS IT? The MXA wrecking crew members have
never been big fans of the airbox design of the 2014–2017
Yamaha YZ450F, nor its little brother, the YZ250F. The
YZ-F airbox is a serpentine maze of tunnels that leads to
a rather underwhelming airbox and miniature air filter.
Twin Air’s new “humpback” airbox kit attempts to rectify
the limitations of the stock YZ450F system by creating
more open space within the airbox to optimize the airflow
to the engine. As a bonus, the bigger airbox allows for a
larger air filter.
WHAT’S IT COST? $314.95 (complete kit); $37.95
(replacement air filter).
CONTACT? www.twinairusa.com or (800) 749-2890.
WHAT STANDS OUT? Here’s a list of things that stand
out with the Twin Air 2014–2017 Yamaha YZ450F airbox
(1) The kit. The Twin Air YZ450F airbox kit comes with
a large fire-resistant Twin Air air filter, humpbacked airbox
lid, aluminum air filter cage, cage-sealing ring, aluminum
air-filter knob and all the necessary hardware. The Twin
Air YZ450F airbox kit also comes with a complete instructions guide, which you are going to need.
( 2) Concept. Twin Air has worked on the YZ450F
airbox since 2010 when it introduced its first YZ450F
Powerflow kit. It required a complete overhaul of the
YZ450F airbox to accept a different air filter, inner airbox
and intake tract. For the 2014 YZ450F, Twin Air didn’t use
such a drastic approach with its Powerflow kit. It focused
on improving the interface between the intake tract and
the air filter by crafting a rigid aluminum sealing ring and
filter cage. There were no major airbox mods. Now, for the
2017 YZ450F, Twin Air has redesigned the YZ450F airbox,
this time focusing on the filter, cage and dimensions of
the airbox cover.
( 3) Installation. Set aside about an hour (with a drill,
jigsaw and 5/32-inch drill bit). In this order, you will: (1)
Remove the upper airbox lid, which includes the upper
half of the air scoops, and drill out the black inner panel’s
plastic rivets and the four metal rivets on the top of the
airbox cover. ( 2) Apply the supplied template to the top
of the airbox cover and cut out the marked area of the
template. ( 3) Put Twin Air’s humpback lid over the holes
and insert the supplied bolts through the holes where the
four metal rivets were. ( 4) Remove the seat and the eight
bolts holding the backfire screen in place. Replace the fire
screen with the CNC-machined aluminum Twin Air cage
(using the eight stock bolts). That’s it! Put the Twin Air
filter in place and install the humpback airbox lid.
( 4) Performance. You don’t need to be Sherlock
Holmes’ practice mechanic to see that the Twin Air
Powerflow airbox kit doubles the size of the YZ450F airbox, allows for a 50-percent-larger air filter (14mm taller)
and eliminates the restrictive wire backfire screen. It gave
MXA’s YZ450F a 1-horsepower increase from mid to top.
Throttle response was improved throughout the range,
and the large filter didn’t need to be cleaned as often as
WHAT’S THE SQUAWK? If you aren’t good at drilling,
cutting and replacing, have Sherlock Holmes’ practice
mechanic do it for you.
Although not the most attractive addition
TWIN AIR YZ450F POWERFLOW AIRBOX KIT
to your YZ450F, the Twin Air’s humpback
airbox kit makes up for ugly in spades.
MXA TEAM TESTED