IS IT? The Moto Tassinari Air4orce is a replacement air boot that fits
between your engine’s throttle body and the airbox. The Air4orce air
boot has its own proprietary shape, plus two removable velocity stacks
that allow you to tune the power.
WHAT’S IT COST? $298.00.
CONTACT? www.mototassinari.com or (603) 298-6646.
WHAT STANDS OUT? Here’s a list of things that stand out with Moto Tassinari’s Air4orce intake system.
(1) Velocity stack. A velocity stack is a trumpet-shaped tube that guides air into the venturi of a carburetor or throttle body. By using Bernoulli’s principle, the large-to-small diameter of the tube increases air velocity, while the length is used to determine the flow characteristics and volume of the air charge. In short, a velocity stack accelerates the air flowing into the carb mouth to the extent that shorter or longer velocity stacks can change the powerband. Moto Tassinari includes a short and long velocity stack with the Air4orce’s system to allow a rider to choose a more responsive low-to-mid (long stack) or more mid-and-up (short stack).
(2) Stock air boots. Most modern four-strokes have velocity stacks designed into their air boots. In the case of Yamaha, the actual air boot is molded into a pseudo-velocity stack design—although it is not tapered and has no fuel velocity benefits. The Honda, on the other hand, has a decent velocity stack that does have some similarities to the longer Air4orce stack. Of the two stock air boots we replaced, the Honda was much more creatively designed than the Yamaha.
(3) Performance. Although we should have been impressed that the Geico Honda, Vance & Hines and Troy Lee teams were using the Air4orce on their race bikes, we conducted a series of track and dyno tests on our own. The results were impressive. With the short Air4orce velocity stack installed, we gained one horsepower at peak and produced more power from 7500 rpm on up to the rev limiter on our YZ250F. Test riders could feel a distinct difference between the short and long Air4orce velocity stacks and between the stock air boot and the Moto Tassinari one. In the end, every test rider selected the short Air4orce stack and reported a noticeable improvement in throttle response, a quicker transition across the low end and more midrange pull. On the dyno, we got one horsepower more at peak.
(4) Installation. The MXA wrecking crew tested the YZ250F and CRF250 Air4orce systems. Both required removing the subframe to get access to the stock air boot and carb. On the Yamaha, the installation was straightforward. On the Honda, it was made much more difficult by the aluminum Twin Spar frame, which blocked access to the front air boot clamp. We removed the shock to make the air boot easier to access on the CRF250.
WHAT’S THE SQUAWK? We had no issues with the Moto Tassinari Air4orce, but we think that Honda should make the engineer who designed their frame-to-air-boot interface change the parts for every Air4orce buyer.
We’d give the Moto Tassinari Air4orce five stars on the Yamaha YZ250F and four stars on the CRF250. It improved the power on both bikes, but the Yamaha’s carb benefitted more than the Honda’s throttle body.
KTM Motorcycle tests