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.