OS MAX-R21 1/8 On-Road



O.S.Engine Nitro Motor R21

Club racers rejoice! The R21 is based on the Championship heritage of the R2102 engine and delivers an unbeatable blend of power and value for 1/8 on-road racing. Its crankshaft and piston/liner are designed with premium performance and easy maintenance in mind, which makes it an ideal choice for beginners. This engine is upgradeable with high-performance O.S. Speed parts, letting you realize your full winning potential. High performance. Low price. That's what you can expect from the R21, only from O.S.


  • The perfect power plant for rookies and club racers.
  • Newly developed crankshaft and piston/liner with the capability to upgrade later to a Spec-class performer.
  • RP7 Turbo glow plug.
  • 8.5 mm carb reducer.
  • Speed flywheel collet.
  • Exhaust seal ring.
  • Dust cap set.


  • Displacement: 3.49cc
  • Bore: 16.08mm
  • Stroke: 17.20mm
  • Port: 5
  • Power Output: 2.75 PS  @ 33,000 RPM
  • Practical RPM Range: 3.000~41.500 RPM
  • Weight: 350g
  • Includes: RP7 Turbo glow plug, exhaust seal ring, 8.5 mm carb reducer, dust cap set


289,00 €

  • disponibile
  • consegna in 1-3 giorni 1

O.S. SPEED R2105 engine only


370,00 €

  • disponibile
  • consegna in 1-3 giorni 1





The O.S. SPEED R21 series won the previous World Championships held in the United States.
The "R2105", most of the parts has been newly designed, aiming for consecutive victories at the world championship to be held in Japan this year.
To increase torque on high-grip track surfaces, a newly designed 9-port sleeve is adopted. O.S. SPEED's traditional DLC coated crankshaft delivers linear power from low to top by changing the counter balance. The outer head has been mirror finish and by clear coat from the conventional color to a silver head base has been adopted. By adopting a thrust plate made out of steel, wear due to interference between the connecting rod and the cover plate during rotation is reduced and engine life is improved.
Adopting the latest design to most part of the engine, it is finished with content suitable for the flagship of the O.S. SPEED on-road engine.

Displacement: 3.49 cc / 0.213cu.in.
Bore: 16.08mm / 0.633 in.
Stroke: 17.20mm / 0.677 in.
Output: 2.80 ps / 2.76 hp / 35,000 r.p.m.
Practical RPM range: 4,000-45,000 r.p.m.
Engine weight: 345.0g / 12.17 oz.
Includes: Reducer(8.5mm RED)/T-RP7 glow plug/Exhaust seal ring(1pc)/ Dust cap set (3mm, 16mm, 18mm 1pc each)

455,00 €

  • disponibile
  • consegna in 1-3 giorni 1

O.S. SPEED R21 SHIMO Edition2


O.S.SPEED R21 SHIMO EDITION 2 Combo Set (1DJ00) TR02 EFRA2165 & MR03-WC We have developed O.S.SPEED R21 Shimo edition collaborated with Takaaki Shimo, a multiple podium winner of the IFMAR 1/8 Racing World Championship. It is a 7-port engine with a new cylinder liner, which has extra holes to reduce overheating. The cooling head and 8.5mm carburetor restrictor are anodized in the special color; champagne gold. The crankshaft is modified to meet his preference, smooth power transition from bottom to the top speed. For the first time we make the combination of TR02 (EFRA2165) silencer with MR03-WC manifold to dedicate to this special edition.


Set combo O.S.SPEED R21 SHIMO EDITION 2 (1DJ00) TR02 EFRA2165 e MR03-WC Abbiamo sviluppato l'edizione O.S.SPEED R21 Shimo in collaborazione con Takaaki Shimo, plurivincitore del podio dell'IFMAR 1/8 Racing World Championship. È un motore a 7 luci con una nuova canna del cilindro, che ha fori extra per ridurre il surriscaldamento. La testa di raffreddamento e il venturi del carburatore da 8,5 mm sono anodizzati nel colore speciale; oro champagne. L'albero motore viene modificato per soddisfare le sue preferenze, una transizione graduale della potenza dalla velocità inferiore a quella massima. Per la prima volta realizziamo l'abbinamento silenziatore TR02 (EFRA2165) con collettore MR03-WC da dedicare a questa edizione speciale.

483,00 €

  • esaurito