⟲ 360° — drag meThe facts.
| Brand | Akrapovic |
|---|---|
| Part number | S-Y4MET16-FDHLTA |
| Fitment | Yamaha YZ450F (2023–2025) |
| Line | Evolution Line (Titanium) — complete system |
| Weight | 3.32 kg (stock 4.17 kg, saving 0.85 kg / 20.4 %) |
| Power | 56.6 PS (stock 54.7 PS, gain 1.9 PS at 10,600 rpm) |
| Torque | 45.8 Nm (stock 45.5 Nm) |
| Note | Highest peak power of the motocross systems in this catalogue |
| Road approval | None — closed course competition use only |
DescriptionThe whole story▼
56.6 horsepower. That is the highest figure of any motocross system in this catalogue, and it comes from Yamaha's reversed-cylinder 450 — the engine that turned the class on its head when it appeared, with the intake at the front and the exhaust running back and down.
Key Features
- Titanium complete system for the 2023 to 2025 YZ450F
- 56.6 PS at 10,600 rpm, 1.9 above the standard 54.7
- 3.32 kg instead of 4.17 kg — 850 grams less
- Torque 45.8 Nm, up from 45.5
- The most powerful motocross setup listed here
The reversed cylinder
Yamaha turned the cylinder around on the YZ450F: the airbox sits where the tank used to be, the intake is straight and short, and the exhaust leaves at the rear before wrapping forward. It gives the header an unusual shape and a longer run than on a conventional motocrosser.
An exhaust for this engine cannot be a generic pipe with different mounts. Akrapovic builds the header to the routing Yamaha's layout demands, and the 1.9 PS is what that specific work is worth.
Where the 850 grams sit
High and behind the rider. On a 450 that is ridden aggressively, mass at the back of the bike affects how quickly the rear will come round and how the machine sits in the air. It is the same argument as on the Kawasaki, and it is the reason full systems outsell slip-ons in this class.
Three model years
2023, 2024 and 2025. Yamaha changed the 450 again for 2026, and that year takes S-Y4MET17-FDHLTA — a separate article with identical published figures.
Not for the road
Closed course competition only. There is no EC or ECE approval and no homologation document for this system.
Why the header shape is the hard part
With the exhaust port at the rear of the engine, the YZ450F header has to leave the head, turn forward under the frame, pass the shock and then run back to the silencer. That is more bends in less space than a conventional layout allows, and every bend costs flow if it is done badly.
Akrapovic forms the pipe rather than assembling it from mandrel bends welded together. The wall stays a constant thickness through the curve and the internal diameter does not step, which is where the 1.9 PS comes from — not from a bigger pipe.
Riding a 450 with 850 grams less at the back
Mass behind the rider and above the axle line is what resists the bike rotating in the air. Take almost a kilogram out of it and a scrub gets easier, a whip comes back sooner and a bad landing is less of an argument.
None of that shows up on a dyno sheet, which is precisely why full systems keep selling in a class where the power gains are measured in single horsepower.
Fitting and what it needs
The complete system replaces the header and the silencer. Akrapovic supplies the springs and mounts; a new exhaust port gasket is a Yamaha part and worth having on the bench before starting.
Three years, then a new number
2023, 2024 and 2025 take this article. From 2026 Akrapovic lists S-Y4MET17-FDHLTA with identical published figures — a different part for a changed chassis rather than a changed engine.
Article number
Akrapovic lists this system as S-Y4MET16-FDHLTA. The optional noise damper for a 109 dB/A limit is V-TUV386.
DownloadsInstructions▼
FitmentWhich bikes this fits▼
- Yamaha YZ450F (2023–2025)
- Complete titanium system
- Closed course competition use only
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