O.S. Speed R21GT Combo Set

Tower Stock# OSMG1032  •  Manufacturer Stock# OSMG2097
Notes from our tech department:
****** Because of the expressed racing nature of this engine, ******
****** it is NOT covered by the O.S. 2 Year Warranty ******


Fully compatible with IFMAR regulations
Crankcase modified from the O.S. R2101 on road engine
Newly designed cylinder and piston with five scavenging ports and
three exhaust ports
DLC coated crankshaft with silicon filler for lighter weight, and
phosphor bronze double counter weights for better torque
Newly designed 22E(B)GT double adjustment carburetor for better
response when cornering with a 7.0mm restrictor which conforms to
IFMAR regulations
O.S. Speed T-2060SC polished aluminum tuned pipe with 180 manifold
Ten fin cylinder head for efficient heat dissipation


O.S. Speed R21GT 1/8 scale GT Racing Engine with Carburetor
RP6 Turbo Type Medium Heat Range Glow Plug
7.0mm Carb Restrictor
Exhaust Seal Ring
T2060SC Tuned Pipe with Manifold
Two Header to Crankcase Attachment Springs
Three Manifold to Pipe Springs
Instruction Manual


Fuel: 10-30% nitro content, 20% recommended for break-in
Glow starter, fueling bottle and track equipment


Displacement: 0.213 cu in (3.49cc)
Bore: 0.633" (16.08mm)
Stroke: 0.677" (17.20mm)
Output: 2.65ps 2.61hp @ 34,000RPM
Practical RPM: 4,000 - 42,000
Engine Weight: 13.2oz (369g)
Crankshaft Threads: UNF 1/4-28
Distance Between Mounting Holes Same Side: 0.83" (21mm)
Distance Between Mounting Holes Opposite Side: 1.45" (37mm)
Height Bottom of Mounting Tabs/Top of Cylinder Head: 3.4" (86.5mm)
Width at Mounting Tabs: 1.8" (45mm)
Width of Crankcase below Mounting Tabs: 1.2" (31.6mm)
Distance from Backplate to Front Bearing: 2.5" (64.6mm)
Distance from Center of Crankshaft to Front Bearing: 1.7" (44mm)
Distance from Center of Crankshaft to Backplate: 0.85" (21.6mm)

Tuned Pipe
Length: 6.6" (167mm)
Pipe Diameter: 1.4" (36mm)
Inner Diameter at Header End: 0.71" (18mm)
Inner Diameter of Exhaust Outlet: 0.31" (7.8mm)

Carburetor Settings, NOTE carburetor is preset at factory and
only requires very small adjustments
Needle Valve: Open 30-45 and gradually close until optimum straight
line speed is achieved during break-in
Metering Needle: Rotate clockwise 15-30 to lean out, 15-30
counterclockwise to richen the fuel/air mixture
Mixture Control Valve: Adjust to produce light smoke during high-
speed running and to increase RPM smoothly during acceleration
after needle valve and metering needle are adjusted

jxs 10/23/19



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