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O.S. SPEED R21GT II Combo Set (1DT01)

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O.S. SPEED R21GT II Combo Set (1DT01)

While inheriting the smooth feeling and good fuel efficiency of the previous model O.S.SPEED R21GT, which was well received in the European market, the home of GT cars, the power feeling in the medium and low speed ranges has been improved by revising the counterbalance of the crankshaft. In addition, the newly designed inner head improves idling performance, and an inner head O-ring is used to reduce vibration and improve dust resistance. The outer head has been made lighter, and has evolved into the O.S.SPEED R21GT II with attention to the detail. We also have a combo set with TB01 (EFRA2042) tuned silencer and MB01-70 manifold.


  • R21GT II Engine
  • TB01 EFRA2042
  • MB01-70


  • Displacement: 3.49 cc /
  • Bore: 16.08mm / 0.633 in.
  • Stroke: 17.20mm / 0.677 in.
  • Output:2.65 ps / 2.61 hp / 34,000 r.p.m.
  • Practical rpm range: 4,000-42,000 r.p.m.
  • Weight:362g / 12.77 oz.

Standard accessories

  • Glow Plug RP7
  • Venturi 7.0MM(RED)AL2
  • Venturi 7.0MM(RED)AL2 Exhaust seal ring
  • Dust cap set(φ3、φ16、φ18)

Product features

The crankshaft uses two tungsten counterweights. We have optimized the mass balance by reviewing the detailed dimensions.

The inner head has been revised. Improved low and medium speed feeling and idling performance. An O-ring is also used to reduce vibration and improve dust resistance.

The weight of the new outer head, compared to previous model has been reduced. Fins of outer head has been machined.

Equipped with 5 scavenging ports and 3 exhaust ports to meet IFMAR regulations.

Equipped with a double-adjust type 22E(B) GT carburetor. The new venturi is 7.0MM(RED) AL2.

COMBOSET comes with TB01 EFRA2042 (T-2060SC) + MB01-70 (M2003SC).