Specifications; Engine; Fuel System - Stihl 021 Service & Repair Manual

3.

SPECIFICATIONS

3.1

Engine

STIHL single cylinder two-stroke engine with special impregnated cylinder bore
Displacement:
Bore: 40 mm
Stroke: 28 mm
Power output to ISO 7293:
Max. permissible engine speed
(with bar and chain):
Idle speed:
Bearings:
Piston pin diameter:
Rewind starter:
Pawls:
Reserve pull on rope rotor:
Starter rope:
Clutch:
Clutch engages at:
Crankcase leakage
test
at gauge pressure:
under vacuum:
3.2

Fuel System

Carburetor:
Standard setting on carburetors
with three adjusting screws
High speed screw H:
Low speed screw L:
Carburetor leakage test
at gauge pressure:
Function of tank vent
at gauge pressure:
under vacuum:
Fuel tank capacity:
Octane rating:
Fuel mixture:
Mix ratio:
Air filter:Box filter, fabric or fleece filter
1)
Not adjustable
2)
021 only up to serial number X 34 944 402
021, 023, 025
021 023 L
3
35.2 cm 40.2 cm
2.15 cu.in 2.45 cu.in
40 mm 40 mm
1.57 in 1.57 in
32 mm 32 mm
1.10 in 1.26 in
1.5 kW (2.0 bhp) 1.1 kW (1.5 bhp)
at 9,000 rpm at 6,500 rpm
1)
11,500 rpm
2,800 rpm
Crankshaft supported in heavy-duty ball bearings, needle cages on
small and big ends
Cylindrical rollers on big end
10 mm (0.39 in)
Pawl engagement
Single pawl system
min. 1/2 turn
3.0 mm (0.12 in) dia.
Centrifugal clutch without linings
3,600 rpm 4,100 rpm
0.5 bar (7.25 psi)
0.5 bar (7.25 psi)
Diaphragm carburetor
Open approx. 1 turn
Open approx. 1 turn
0.8 bar (11.6 psi)
≤ 0.3 bar (4.35 psi)
≤ 0.05 bar (0.725 psi)
0.47 l (1 US pt)
min. 90 RON (US/CAN; pump octane min. 87)
Regular brand name gasoline
and two-stroke engine oil
50:1 with STIHL two-stroke engine oil
25:1 with other brand name two-stroke, air-cooled engine oils
023
3 3
40.2 cm
2.45 cu.in
42 m
1.57 in
32 mm
1.26 in
1.9 kW (2.6 bhp)
at 9,500 rpm
12,500 rpm
2)
3,500 rpm
025
3
45.4 cm
1.8 cu.in
42,5 mm
1.7 in
32 mm
1.26 in
2.2 kW (3.0 bhp)
at 10,000 rpm
13,000 rpm
3,500 rpm
3