Magnum XL91 RFS Blue 4-Stroke

Tower Stock# LXXRH4  •  Manufacturer Stock# 210868
Magnum XL91 RFS Blue 4-Stroke (large view)
Notes from our tech department:
This is the Magnum XL91 RFS Four-Stroke Aircraft Engine
with Blue Rocker Cover.


Aluminum piston, iron piston ring and steel cylinder sleeve for long
life and high power output
Dual ball bearing supported crankshaft and camshaft
Dual needle valve carburetor insures precise fuel/airflow metering
High-flow muffler
One year limited warranty through manufacturer


Magnum XL91 RFS Four-Stroke Engine with Muffler, instruction manual
and parts list


Fuel: For break-in, 10% 2-stroke airplane blend
For normal use, 15% 4-stroke airplane blend
Glow Plug: 4-stroke "hot" type
Break-in Propeller: 14x6
Glow starter, fuel tubing and field equipment


Displacement: 0.91 cu in (15cc)
Bore: 1.09" (27.7mm)
Stroke: 0.97" (24.8mm)
Crankshaft Diameter: 5/16"
Practical RPM: 2,000 - 12,000
Weight with Muffler: 22.4 oz (635g)
without Muffler: 20.7oz (587g)
Distance Between Mounting Holes Same Side: 1.02" (26mm)
Distance Between Mounting Holes Opposite Side: 2.04" (52mm)
Width at Mounting Tabs: 2.4" (60mm)
Height from Bottom of Mounting Tabs to Rocker Cover: 4" (101mm)
Height from Bottom of Crankcase to Rocker Cover: 4.7" (120mm)
Distance from Backplate to Front Bearing: 2.9" (74mm)
Distance from Backplate to end of Crankshaft: 4.9" (125mm)

High Speed Needle: Turn in completely then back out 2-1/2 turns
Low Speed Needle: Do NOT adjust until engine is broken in. Hold carb
barrel open, turn needle screw counter-clockwise until it stops
then turn in clockwise 4-1/4 turns-this is the factory setting


Some Differences Between 4-Stroke and 2-Stroke Engines;
4-strokes are quieter.
4-strokes get better fuel economy.
2-strokes generate more RPM
4-strokes generate more torque and will swing a larger prop.
4-strokes have a realistic sound; like a real aircraft engine.

jxs 7/02/09

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