REDS 521 Sport S-Line .21 Off-Road Competition Nitro Buggy Engine

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REDS 521 Sport S-Line .21 Off-Road Competition Nitro Buggy Engine
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Price: $289.99

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The REDS 521 Sport .21 Off-Road Competition Buggy Engine offers a balance of innovation, quality and performance at a mid range street price. The 521 Sport features technical changes in the 5 port sleeve, combined with updated materials to offer users high reliability, tuning stability and fuel mileage. The 521 Sport guarantees excellent performance at a reasonable price.

It is recommendable to match the engine with the REDS 2143 + M, or XONE Torque tuned pipe.


  • ALUMINUM CARBURETOR: 521 Sport engine includes the same aluminum carburetor as 721 engines to guarantee reliability and tuning stability. The insulator bushing has been improved with aerospace grade ultra high strength polymer. Furthermore, the GEN2 carburetor features a double grub screw joint link to allow positioning and fitting with the any servo linkage system.
  • STATE OF THE ART DIE CASTING: The unique high stiffness crankcase design is produced with a high quality pressure die casting process and special aluminum alloy developed by REDS Racing engineers to guarantee higher stiffness and strength.
  • 5 PORT TECHNOLOGY: The piston and sleeve features updated materials. Thanks to updated 5 port technology, this engine provides really good fuel mileage and a smooth power band.
  • HANDMADE, TUNED AND ASSEMBLED: Every single engine is hand inspected and compression checked inside REDS Racing headquarters by Mario Rossi to achieve the highest quality standards.
Category: 1/8 Buggy and Truggy
Displacement: 3.5cc
Bore: 16.2mm
Stroke: 16.9mm
Intake ports: 5
Exhaust ports: 1
Front Bearing: 7x19x6mm rubber seal
Rear Bearing: 14x25.4x6mm Swiss made steel
Carburetor Venturi: 7.0mm (6.0, 6.5, 7.5, 8.0 optional)
Carburetor: VCX2-A Aluminum Short needle
Weight: 345g
Fuel consumption: > 9:00 min
Engine temperature: 110-130°C
Recommended Glow plug: REDS TS3
Recommended pipe: REDS 2143 + M or XONE Torque
Recommended fuel: 25-30% nitro, 8-10% oil
Break-in fuel: 12% oil

This product was added to our catalog on June 29, 2021

Sunday, Feb 13 2022 (about 2 years ago)
REDS 521 Sport S-Line .21 Off-Road Competition Nitro Buggy Engine
Very pleased with this engine. Good power and easy to break in. REDS also updated the engine with a tuned and balanced crank (still raw steel though) and what seems to be some sort of lapping if the piston and sleeve. The “gen 2” or updated version was much easier to start for the first time than the original. It idled very smooth right off the bat and holds its temp very well. The intent of this engine is supposed to be a budget friendly, entry-ish level engine and the updates really fulfilled the purpose. It makes operating this engine very smooth and easy. Very good engine for $270
Jeremy Williams
Wednesday, Jul 7 2021 (about 3 years ago)
REDS 521 Sport S-Line .21 Off-Road Competition Nitro Buggy Engine

I hope this works. This is a thorough video review of the 521 sport!!! Really well done!! Awesome details covered and why!!
Verified Owner
Wednesday, Jan 4 2023 (about a year ago)
REDS 521 Sport S-Line .21 Off-Road Competition Nitro Buggy Engine
Reds make some fantastic engines. One of my favorite nitro engines I own. Idles great and plenty of power. Will be buying more when needed for other buggies.