REDS 521 Sport .21 Off-Road Competition Buggy Engine Combo w/2143 Pipe & M Manifold

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REDS 521 Sport .21 Off-Road Competition Buggy Engine Combo
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Price: $339.99

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The REDS 521 Sport .21 Off-Road Competition Buggy Engine Combo with 2143 tuned pipe and M manifold (REDKM210011), 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.


  • 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

Verified Owner
Saturday, Sep 3 2022 (4 weeks ago)
REDS 521 Sport .21 Off-Road Competition Buggy Engine Combo
Amazing high Torque.......................
Verified Owner
Saturday, Nov 13 2021 (10 months ago)
REDS 521 Sport .21 Off-Road Competition Buggy Engine Combo
I bought this as an upgrade for my TLR buggy rocking the 5R5 engine combo I bought almost a year ago. Comparing it to a Reds 721 SV it looks and feels almost identical. The engine has a tight pinch, even after Adam Drake's EBIS it was still a little tight and wore a small groove in my starter box wheel. Engine sounds impressive, feels like more torque compared to the 5R5, plus the carb slide is sealed, looks like the 721 SV I have in my TLR Truggy. Using 25% Torco with a splash of klotz for good measure. I like to keep things lubed up when my engines are singing to the angels!
Tuesday, Sep 14 2021 (about a year ago)
REDS 521 Sport .21 Off-Road Competition Buggy Engine Combo
Still going to break through myself but so far so good definitely quality. And price is great way better than R5R in my opinion. And I'll update after I get it broke in and get a few races on it!i expect great things from this power unit!!!???
Verified Owner
Sunday, Aug 22 2021 (about a year ago)
REDS 521 Sport .21 Off-Road Competition Buggy Engine Combo
I saw the last review and agree, this motor is super tight but settles down nicely after a gallon and a half. reminded me of breaking in an alpha. Ive run three gallons of bones 25/10. At first I didn't like the new carb, but im getting the swing of it and it does drop right straight down to idle when tuned proper. It drives great, mines in a truggy, its a bottom end motor with a ton of punch, with less of a top end. I took it apart after each gallon and everything looks great, typical Reds quality.
Verified Owner
Monday, Aug 16 2021 (about a year ago)
REDS 521 Sport .21 Off-Road Competition Buggy Engine Combo
So far I've only gotten a half gallon through this engine but I can say it's running really well. The only downside I can say for the whole engine is the pinch is really tight. So tight that from the first time I started the motor, even after getting to 200 before starting, that I have worn a decent grove in the starter box wheel. Also keep a tool handy to get it out of TDC when it gets stuck because it will. After a gallon I will update this post.