Kawasaki Ninja ZX-6R 636 (2013–2026) Velocity Stacks — PA12-CF
Kawasaki Ninja ZX-6R 636 (2013–2026) Velocity Stacks — PA12-CF
Built for the airbox, not adapted to it
A velocity stack only does its job if it sits where the engine wants it. This set is a staggered pair of lengths — the longer pair for cylinders 2 and 3, the shorter for 1 and 4 — matched to the airbox roof clearance so the bell mouths sit in clean air rather than against the lid.
Each stack seats directly onto the throttle body with no adapters, no trimming and no hardware. The mouth is a continuous radiused bell, blended into a straight throat, so the air turns once and keeps turning the same way.
Carbon-fibre nylon, because an airbox is a hostile place
These are printed in PA12-CF — nylon 12 reinforced with 20% chopped carbon fibre. It is the same polymer family the industry uses for fuel lines, and that is the point: an intake sits in heat, vibration and fuel vapour, and most printed parts are made from materials that tolerate none of the three.
Published properties for the material:
| Heat deflection | 176 °C |
| Tensile strength | 86–100 MPa |
| Elongation at break | 13.7% |
| Carbon fibre content | 20% |
That last number matters more than it looks. Elongation is toughness — the ability to absorb a vibration cycle instead of cracking through it. Carbon-filled PET and PETG typically manage a third of it. An intake tract is a fatigue environment, and stiffness without toughness is how parts fail there.
Spacers included
Four spacers ship with the set. They set the stack height in the airbox and let you run the geometry as designed rather than as it happens to land.
Made in Indianapolis
Designed, produced and inspected in-house. Every set is dimensionally checked against the reference datums before it ships.
Key features
- Tuned-length set — longer pair for cylinders 2 and 3, shorter for 1 and 4
- PA12-CF construction — nylon 12 with 20% chopped carbon fibre, 176 °C heat deflection
- Fuel- and heat-resistant — the polymer family used for automotive fuel lines
- Direct fit — seats on the throttle body, no adapters, no trimming, no hardware
- Continuous radiused bell mouth blended into a straight throat
- Four spacers included to set stack height
- Designed and made in Indianapolis, USA
Specifications
| Fitment | Kawasaki Ninja ZX-6R 636, 2013–2026 |
| Material | PA12-CF (nylon 12, 20% chopped carbon fibre) |
| Finish | Matte carbon black |
| Heat deflection temperature | 176 °C (material) |
| Tensile strength | 86–100 MPa (material) |
| Set contents | 2 × long stack, 2 × short stack, 4 × spacers |
| Installation | No adapters, trimming or hardware required |
| Origin | Designed and manufactured in Indianapolis, Indiana, USA |
What’s in the box
- 2 × long velocity stack (cylinders 2 and 3)
- 2 × short velocity stack (cylinders 1 and 4)
- 4 × stack spacer
- Fitting instructions
FAQ
Will these fit my year?
The set is built for the 636-engined ZX-6R. Check your year against the fitment finder before ordering — the ZX-6R has run both 599 cc and 636 cc engines across its life, and they are not interchangeable.
Do I need to re-tune?
Any intake change alters how the engine breathes. On a stock or lightly modified bike most riders run them as-is; if you are already running a tune, have your tuner account for the change.
Is this a track-only part?
The set does not alter emissions equipment. Check your local regulations for road use.
Why nylon and not aluminium or carbon fibre?
Weight, and the shape. A radiused bell is expensive to machine and awkward to lay up. Carbon-filled nylon gets the geometry right, survives the environment, and does not add mass at the top of the engine.
Can I buy a single stack?
The set is sold complete because the lengths are staggered; a single stack would not be the right length for an arbitrary cylinder. Contact us for replacements.