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H-D Sportster S 1250 ‘SPS 4’ customized by Thunderbike

H-D Sportster S 1250 ‘SPS 4’ customized by Thunderbike


The Sportster S, boasting a modern chassis and the remarkably agile Rev-Max 1250T engine, not only offers a broad rev range due to its variable timing but also packs a staggering peak power of 122 hp on the road. This makes it an ideal foundation for Thunderbike’s supersport custom projects.

In this instance, their project underwent significant modifications. They incorporated the sporty GT wheels, sized 6.00 x 18 inches at the rear and 3.50 x 21 inches at the front. A groundbreaking development involved the redesign of the Sportster S’s front wheel to accommodate dual brake discs for the first time.

This required new milled brake caliper mounts for the upside-down fork and the addition of a Brembo radial brake caliper. To enhance responsiveness, they also coated the stanchions in gold DLC.

To complement the sporty concept, the bike received a revamped seating position through Thunderbike’s relocated footrest system and custom triple clamps with mounts for a flat handlebar specifically crafted for the Sportster S. This adjustment ensures that the riding position aligns perfectly with the bike’s new dynamics.

The alteration to a 21″ front wheel and 340 mm brake discs not only enhances the bike’s sporty appearance but also boosts its agility. The slimmer front tire notably improves handling, while the upgraded brake system, featuring dual-disc brakes, delivers exceptional performance.

The project incorporates meticulously crafted parts from Thunderbike’s SPS series, including the radiator cowling, engine cover, pulley cover, shock absorber cover, headlight cowling, grips, indicators, and more, all finely milled. The paint scheme, conceptualized by Kruse Design, consistently underscores the bike’s sporting ambitions.

The sleek exhaust system from J&H seamlessly integrates with the overall design. Additionally, the seat, crafted by Spirit Leather, not only enhances aesthetics but also offers optimized support with its improved shape.

Thunderbike parts

  • Thunderbike Front Fender SP-S
  • Thunderbike Windshield Kit black
  • Thunderbike Triple Tree SP-S contrast cut
  • Thunderbike Turn Signal Set Quick-Stripe 54mm Dark black
  • Thunderbike Taillight & Turn Signal Kit black
  • Thunderbike Mirror Bracket Set black
  • Thunderbike Side Mount Licence Plate Bracket medium black matt

  • Thunderbike License Plate Frame Inside Plate
  • Thunderbike License Plate Lighting
  • Thunderbike Shock Adjusting Knob satin black
  • Thunderbike Foot Controls SP-S recessed contrast cut
  • Thunderbike Rider Footpeg Set SP-S black
  • Thunderbike Shift-Peg satin cut
  • Thunderbike Grips SP-S satin black cut

  • Thunderbike Pulley Cover front contrast cut
  • Thunderbike Frame Cover black
  • Thunderbike Radiator shroud set bicolor
  • Thunderbike Clutch Cover SP-S
  • Thunderbike Timer Cover
  • Thunderbike Heat exchanger Cover black

  • Thunderbike Alternator Cover SP-S
  • Thunderbike Belt Guard black
  • Thunderbike Swing Axle Cover black
  • Thunderbike Handlebar SP-S1 Alu 80.5cm black matt
  • Thunderbike GT Wheel
  • Thunderbike Brake Disc Vegas Floated 340mm
  • Rizoma Mirror Dynamic black