DEXTER RACING Item number: DEX50N28
DEXTER RACING

Quick overview - Classic Box 3.0

Torque from the bottom, coasting >9 000 /min
No short 4th gear required (wide band)
O-ring manifold (tight & easy to service)
Tires: 3.00-10 / 90/90-10; close to stock volume/optics
Variant Ø28 mm: 75-112/115-130 cc (short stroke/classic setups)
Variant Ø32 mm: ≥133 cc and powerful setups
259,00 €*
available immediately
Shipping weight 3,6 kg

Dexter Racing × W1R "Classic Box 3.0" - Smallframe Exhaust Ø28 / Ø32 (50-144 cc)

Box system developed in collaboration with W1R - WhiteOneRacing. Delivers rich torque from the bottom like a Proma "banana", revs out significantly further and achieves higher peak power. Two versions: Ø28 mm for short-stroke 75-112/115-130cc, Ø32 mm for 133 cc and larger. On conventional setups, >9,000 /min can be easily achieved.

Characteristics

Box layout with short diffuser section: early pressure build-up, good speed stability
Broadband layout - stable connection of the upper gears
Comparison with the Proma: similar acceleration, but more peak power and higher revs
Reduced noise level with close-to-production look

Technical data & variants

Versions: Ø28 mm manifold for 75-112/115-130 cc, Ø32 mm for ≥133 cc
Tires: suitable for 3.00-10 or 90/90-10
Fitting: without frame work on 50 Special / V50 (N/L/R), PK (S/XL/XL2), HP/FL2, ETS; also fits 125 Primavera frame with glove compartment
Manifold connection: O-ring sealed (plug-in system)
Gearbox: usable 4th gear - short 4 usually not required

Compatible vehicle models (selection)

V50 (N, L, R), 50 Special
V90, 90 SS (Super Sprint), 50 SS
100 / 100 Sport, 125 Primavera, 125 ET3
PK 50/75/100/125 S
PK 50/125 XL, PK 50/125 XL2
PK 125 ETS, PK HP / FL2

Not suitable for PK "Automatica" (different engine/exhaust flow).

Installation without cutting on V50/50 Special (short & long stroke / 43 & 51)
Fits ET3/125 Primavera chassis with glove compartment
Tire clearance given with 3.00-10 and 90/90-10; check brake/suspension travel for special rims

Performance character (dyno note)

Comparative measurements, e.g. on Polini 130 twin intake, show the typical box characteristics: early torque, clean mid-range and sustained revving - higher peak power and more rev reserve compared to a Proma.

FAQ - Frequently asked questions about the "Classic Box 3.0"

Ø28 mm for 75-112/115-130 cc (short-stroke setups, classic rotary valve/reed configurations). Ø32 mm for ≥133 cc or clearly performance-oriented setups with higher throughput.
Generally not. The box provides enough connection to use the standard transmission with a full 4th gear.
The revised chamber geometry reduces noise development; subjectively quieter than Proma with a near-standard look.
Tuning/racing component without E-marking. Observe national regulations. Warranty according to the manufacturer's instructions for the modified components (cone manifold, weld seams, tailpipe).
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