Novarossi KEEP OFF 21-4 Tuned .21 Off Road Engine (Turbo) (Ceramic Rear)

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This is the Novarossi KEEP OFF 21-4 4-Port .21 Competition Off Road Engine. The KEEP OFF includes all the tricks and tweaks that Novarossi has developed for their off-road engines, most notably a unique and patented bearing design that reduces the inertia of the rotating mass and increases the engines scavenging, delivering increased throttle response and higher top speed. This, combined with a factory tuned crankshaft, and 4-port sleeve deliver the best combination of linear power delivery and minimal fuel consumption possible. Additionally, the Evolution 2 cooling head was chosen to keep the cooling head mass as low as possible, and the re-designed exhaust gasket helps to increase the life of the gasket.


  • Cooling Head: The 'Lighter & Lower Evolution 2' cooling head has been drilled and milled out to reduce the mass of the cooling head, lowering the Center of Gravity of the engine/car.         
  • Sleeve: The sleeve has 4 transfer ports, the best option to provide linear power with minimal fuel consumption.
  • Crankshaft: This engine is "Factory Tuned" and features a modified crankshaft to further improve the power output and driveability.
  • Gasket: The inner shape of the gasket has been redesigned to allow the use of more material and when combined with an updated material is more resistant to high temperatures.
  • Conrod: The R7 conrod is machined from a super light aluminum that has been checked ultrasonically. The unique shape of the R7 rod creates less turbulence inside the engine.
  • Backplate: The shape of the rear cover helps to optimize the crankcase filling and reduces dead space. The steel plate helps to reduce friction and increases the life of the rod.
  • Carburetor: The plastic carburetor is a "reverse" type with a sliding throttle valve.
  • Rear Ball Bearing: The ceramic rear ball bearing reduces the inertia of the rotating mass and increases the engine's scavenging ability. The bearing, combined with the re-designed case provide increased throttle response and higher top speeds.
Recommended Tuned Pipes: 51006M, 51016, 51020M
Recommended Manifolds: 41021, 41029, 41030

Recommended Glow Plug:
  • C5TGC: For ambient temperature - 32°F/50°F (0°C/10°C)
  • C6TGC: For ambient temperature - 50°F/77°F (10°C/25°C)
  • C7TGC: For ambient temperature - 77°F/104°F (25°C/40°C)
Displacement: 3.49 cc
R.P.M. (max power): 36,000 RPM
Practical Range: 6,000-38,000 R.P.M.
Bore x Stroke: 16.26x16.80 mm
Sleeve: 4 ports
Rear Ball Bearing: ceramic
Front Ball Bearing: steel
Crankshaft: 14 mm - turbo - tuned
Carburetor: plastic - 9 mm - reverse
Glowplug: Turbo (C6TGC)
Exhaust Position: rear
Weight: 360g
Fuel type: 25% nitro

This product was added to our catalog on March 29, 2013

Verified Owner
Monday, Sep 9 2013 (about 6 years ago)
Novarossi KEEP OFF 21-4 Tuned .21 Off Road Engine (Turbo) (Ceramic Rear)
Great engine with a nice bottom end. Not quite the top end that the 7 port engines benefit from but on the tight/complex tracks that I race on it is really very good. I have had no problems running 10 minutes on the NR 2096 pipe and I really recommend this engine for competition use.
Verified Owner
Thursday, Nov 2 2017 (about 2 years ago)
Novarossi KEEP OFF 21-4 Tuned .21 Off Road Engine (Turbo) (Ceramic Rear)
Broke it in with 1/2 a gallon of 25/11 and then put my normal 25/9 in it. Haven't gone hard on the tune yet but we are close and this thing is a screamer. Not quiet the power level of my B2102 but the ease of tuning and power delivery honestly make this engine quicker around my home track. The low end with a 41001 and a 9886 make it very linear and controllable. It's not ballistic up top but no slouch at all. Tuning is extremely easy, very little adjustment as been needed at all from box stock to almost race ready. It's not flamed out in a pit stop once even with a nice low idle and I'm seeing 8:30 a tank with a still tight engine and not leaned out completely. Not a single complaint, very strong and so far reliability of the idle makes it a winner in my book.