O.S. R21 1/8 On-Road Club Racer Engine

Tower Stock# OSMG2032  •  Manufacturer Stock# 1B900
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Notes from our tech department:
This is the O.S. Engines R21 Engine for 1/8 scale On-Road Club Racers.


Nine fin anodized aluminum cylinder head in blue
21M2 slide valve carburetor with 8.5mm reducer
Silicone filled crankshaft
Two year limited warranty through Hobby Services beginning at date of


R21 Engine with 21M2 Slide Valve Carburetor and Instruction Manual
RP7 Turbo Glow Plug, 8.5mm Carb Reducer Dust Cap Set


Fuel: Car blend, 25% nitro content recommended for break-in
Exhaust System depending on vehicle, the O.S. Engines T-2080C Tuned
Silencer Set (OSMG2983) is a good fit for this engine
Glow Starter and Track Equipment


Displacement: .213 cu in (3.49 cc)
Bore: 0.633 in (16.08 mm)
Stroke: 0.677 in (17.2 mm)
Output: 2.75ps / 2.71 hp / 32,000 RPM
Weight: 12.35 oz (350 g)
Practical RPM: 4,000-44,000
Crankshaft Size: UNF 1/4-28
Distance between Mounting Hole Centers Same Side: 0.83" (21mm)
Distance between Mounting Hole Centers Opposite Side: 1.4" (37mm)
Height Bottom of Mounting Tab/Top of Cylinder Head: 3" (75.6mm)
Height Bottom of Crankcase/Top of Cylinder Head: 3.6" (91.2mm)
Height Bottom of Mounting Tab/Exhaust Outlet Center: 1.1" (28mm)
Length from Cover Plate to Front Bearing: 2.5" (64.5mm)
Length from Cover Plate to End of Crankshaft: 3.7" (94mm)
Length from Cover Plate to Center of Crankcase: 0.81" (20.5mm)
Length from Crankcase Center to Front Bearing: 1.7" (44mm)
Length from Crankcase Center to End of Crankshaft: 2.9" (73.5mm)
Carburetor Settings;
Needle Valve: 3 turns open from fully closed
Mixture Control Valve: Flush with carburetor body, adjusting range
within +- 1 turn
Metering Needle: Standard position, flush with ball link body
Throttle: Approximately 0.5mm open from factory setting with reducer

jxs 12/27/17



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