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O.S. - OSMG1992 OSM11685 11685 531028022201 4531028022201
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O.S. 12XZ Speed Spec III Engine
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O.S. 12XZ Speed Spec III Engine
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Instruction Manuals: Manual 1 (2.5 MB)

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Tech Notes
This is the 12XZ Speed Spec III Glow Powered Touring Car Engine
from O.S. Engines.

****** Because of the expressed racing nature of this engine, ******
****** it is NOT covered by the O.S. 2 Year Warranty ******
****** per page 8 of manual. ******


Redesigned head button for better performance and improved
Tapered surface on piston with a depression that works with the head
button to maximize combustion and power
Slightly thicker cylinder liner with redesigned ports for better air/
fuel flow that boosts mid-speed torque and extends fuel mileage
Redesigned 12F2 (B) slide valve carburetor delivers sharp
acceleration and instant throttle response with easier more
reliable tuning
DLC coating on crankshaft with pressed in Tungsten weights and
ceramic rear ball bearing
Outer head sits 0.24" (6mm) lower over the crankcase decreasing the
engine's weight, lowering the CG and aiding in cooling


12XZ Speed Spec III Engine, with 12F2(B) Slide Valve Carburetor,
RP6 Glow Plug, Exhaust Seal Ring, Dust Cap Set, 5.5mm Red Carb
Reducer and Instruction Manual


Fuel: 10-30% nitro content, 20% recommended for break-in
Exhaust System: Depending on vehicle
Air cleaner assembly, glow starter and track equipment


Displacement: 0.128 cu in (2.1cc)
Bore: 0.543" (13.8mm)
Stroke: 0.55" (14.0mm)
Practical RPM Range: 5,000-44,000
Output: 1.73hp @ 35,000 RPM
Weight: 7.9oz (225g)
Height from crankcase bottom to top of cylinder head: 3.2" (82mm)
Height/crankshaft center to top of cylinder head: 2.7" (68.7mm)
Width including mounting tabs: 1.5" (39mm)
Crankcaase width below mounting tabs: 1.02" (26mm)
Width between mounting hole centers same side: 0.43" (11mm)
Width between mounting hole centers opposite side: 1.2" (31.4mm)
Mounting hole diameter: 0.12" (3mm)
Cylinder head diameter: 1.9" (49mm)
Length from end of crankshaft to front bearing: 1.2" (29.5mm)
Length from backplate to front bearing: 2.1" (52.6mm)
Length from backplate to end of crankshaft: 3.2" (82.1mm)
Crankshaft Size: 1/4-28
Carburetor Settings:
Needle Valve, 2.5 turns open from fully closed
Throttle Stop Screw, 0.5mm open
Mixture Control Valve, follow break-in procedure and turn
clockwise 15 to lean mixture or counterclockwise 15 to richen
(Make adjustments only in small increments. Refer to manual for
full break-in and carburetor adjustment instructions)


Some notes on Slide Valve and Rotary Carburetors:
Rotary Carbs offer a larger response in the middle of the power
band. This works well for off-road applications when throttle
response must be varied.
Slide Valve Carbs provide greater response at the beginning and end
of the power band. This works well for on-road and racing
applications for fast take-offs and high speed.

jxs 12/31/12

– If you need more information, use these O.S. resources –
Email: enginesupport@hobbico.com
Web Site: http://www.osengines.com/
Phone: 217-398-8970
  Postal Address:

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Accessories Needed
This is the O.S. 12XZ(P) Speed Spec III On-Road Engine. FEATURES: DLC coated, silicone filled crankshaft with tungsten weight & ceramic rear bearing, 12F2(B) slide valve carburetor REQUIRES: Fuel and track equipment, exhaust system depending on vehicle

Accessories for the O.S. 12XZ Speed Spec III Engine

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