REDS R5R RACER 4.0 .21 Off-Road Competition Nitro Buggy Engine w/HCX (Turbo)

REDS R5R RACER 4.0 .21 Off-Road Competition Nitro Buggy Engine
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Price: $255.99
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The perfect synthesis of innovation, high quality and great performance at a mid range street price. Everything that makes the 4.0 unique today is an extraordinary step forward. The R5R has been redesigned with a 5 ports sleeve and crankshaft timing. The engine is designed with improved fuel efficiency and drivability in mind, and is suitable for both Buggy and Truggy.

R5R Racer tuned by M.Rossi guarantees the same performance as a Pro engine at reasonable price. The 4.0 is one of the most advanced and innovative products on the market, equipped with the best technology to improve reliability and guarantee the best performance on all terrains: HCX horizontal carburetor, silicon filled and tuned crankshaft, sleeve with 5 inlet ports and classic exhaust port, high sealing front bearing, rear steel high quality chrome steel bearing.

"REDS Racing R5R is a real beast. It provides high torque, incredible power, and good runtime. This is a race bred engine you can use in your Truggy, and also in Buggy when you need the extra power.” -Cole Ogden


  • ADVANCED HCX CARB SYSTEM: The revolutionary carb features a top end needle positioned horizontally, lower down on the carb body. HCX Horizontal carb main features: higher idle stability, more precise tuning, easier access to high speed needle, higher mid/top range power.
  • LIGHTWEIGHT & LOW GRAVITY CENTER: The REDS Factory Tuned line was designed to be not only more powerful and reliable but lighter and with lower center of gravity than ever before. To do that, they started from scratch, redesigning each essential part like crankcase, cooling head, combustion chamber and backplate.
  • HANDMADE, TUNED AND ASSEMBLED: The 4.0 is hand-tuned by M. Rossi. Every single engine is hand inspected and compression checked inside REDS Racing headquarters by Mario and Marco Rossi to achieve the highest quality standards. This is core to the values that makes the 4.0 different from any other engine brand on the market.
  • LONG STROKE: The R5R crankshaft is surprisingly strong and reliable thanks to a special steel and heat treatment. Special silicone filling reduces rotating mass.
  • 5 PORTS & BOOSTERS: The sleeve with 5 inlet ports and exhaust port with boosters guarantees high power at each RPM and low fuel consumption. The REDS flat piston, made from a high strength aluminum bar, is a true masterpiece of engineering.
  • FLAT BILLET PISTON: The flat piston matched to a specific combustion chamber guarantees high performance and low consumption. The connecting rod is lightweight, durable and reliable, and the slim shape is designed to minimize aerodynamic friction.
  • HIGH QUALITY BALL BEARINGS: The high sealing and high reliability made in Japan front ball bearing ensures high idle stability. The steel Swiss Made rear bearing ensures longer life and low friction at high temperatures.
Category: 1/8 Buggy or Truggy
Displacement [cm^3]: 3.5
Bore [mm]: 16.2
Stroke [mm]: 16.9
Inlet ports: 5
Outlet ports: 3
Front ball bearing dimension DixDexS [mm]: 7x19x6
Front ball bearing features: rubber seal made in Japan
Rear ball bearing dimension DixDexS [mm]: 14x25.4x6
Rear ball bearing features: Swiss made steel
Carburetor diameter [mm]: 7
Carburetor: HCX Long needle
Weight [g]: 360
Cylinder system: ABC
Exhaust type: rear
Recommended Glow plug: REDS T5C
Recommended pipe: REDS 2143 + S
Recommended fuel: 25-30% nitro, 8-10% oil
Break-in fuel: 12% oil

This product was added to our catalog on June 1, 2016

Sunday, May 14 2017 (about 3 years ago)
REDS R5R RACER 4.0 .21 Off-Road Competition Nitro Buggy Engine
(Reds R5R V3.0)w/HCX carburetor.
I have no experience with the 4th version of this nitro motor from Red's, but I own the previous version of this engine(V3.0) w/ HCX carb. My opinion of this budget engine is of the highest regard. The engine was absolutely the easiest to break in(preheating first 10 [email protected]+F) using a high oil content fuel of your choice and a hot glow plug(OS P3) to keep engine responsive during overly rich conditions during the initial start, and up to tank #10. Then at that point, switch out glow plug for a Reds#5 and your favorite racing fuel. Please use conservative needle settings during the first .5 gallons to ensure maximum life expectancy of engine. I'm very happy with the extremely consistent performance and temperature control with the HCX style carburetor. This engine is very smooth and has a great note coming from the tuned pipe that we all love. I do think that a few things can be improved, but for 255$, how do you lose. Great engine and wins the price vs performance category. High recommended for the club racer or the veteran basher. Good Luck
Verified Owner
Monday, Jun 10 2019 (about a year ago)
REDS R5R RACER 4.0 .21 Off-Road Competition Nitro Buggy Engine
I have purchased 3 of these motors in past 2 years and have paired each of them with the REDS 2104 Smooth pipe. I also added the ProTek RC 14x25.4x6mm Ceramic MX-Speed Rear Engine Bearing to 2 of them. I have very pleased with the fuel economy (9:30-10:30) with Ceramic installed, it can go longer but that depends on your tuning skill and how you drive when racing. Very easy to tune and holds its tune well. Great little race motor whether your club racing at your local track or for Regional events.
Verified Owner
Sunday, Jan 12 2020 (9 months ago)
REDS R5R RACER 4.0 .21 Off-Road Competition Nitro Buggy Engine
I got this engine on sale so I had it modified it’s amazing great fuel economy and it makes loads of power in a nt48.3. The engine tunes easy. Idles all day. Every thing you want in a nitro engine. Two things tho the rod is snug on the shaft hard to get off... also the pinch on break in/run in was crazy with heat and a lapped piston.