Technical Information · issue 3 of 1995
Uprated engine BG 72
Model BG 72 blowers from machine number
IssueTI 3/1995
From serial 31 409 901
Full text
Page 1 of 3
Technical Information
03.95
Model BG 72 Blower - Series 4227
Uprated engine
Model BG 72 blowers from machine number
X 31 409 901=will come with an uprated engine.
Engine power has been increased approx. 8% to
0.7 kW (0.95 bhp).
This boost in power has been achieved by:
• Different port timing
• Higher compression ratio
• Enlarged inlet port
• Modified transfer ports
• Modified gasket and spacer flange
The factory will supply the new versions of the
cylinder, gasket and spacer flange as universal
replacement parts.
&\OLQGHU
Compared with the original version of the cylinder,
the new version can be identified by its approx.
3 mm (0.12 in) higher base flange and larger inlet
opening.
Longer M5 x 20 screws are necessary to mount the
new cylinder (instead of the previous M 5 x 16
screws).
10,5
When installing a new uprated cylinder on a
9
machine with the older cylinder design be sure to
10
7
also install the longer 5 x 20 mm screws to avoid
damage to the cylinder and crankcase.
15 19
356TI001
Original New
version version
)Technical Information 03.95 - Page 2
*DVNHW
The new gasket’s inlet port window is 19 mm
(0.75 in) wide compared to 16 mm (0.63 in) in the
original version. The new gasket may be installed
in older machines.
16 mm 19 mm
325TI002
(0.63 in) (0.75 in)
Original gasket New gasket
Spacer flange
The opening at the cylinder side of the new spacer
flange is 19 mm (0.75 in) wide. See service notes
before installing the new spacer flange in older
machines.
Service notes
Only the QHZ versions of spare parts may be used
for=rep~irs=to=the=new machine versions=since=~
loss of power and engine running problems may
otherwise occur.
An increase in engine power on older machines
to approx. 0.7 kW (0.95 bhp) is possible only if
all the new parts=~re=inst~lledK
3
4
The new cylinder must be secured with the
325TI001
M5 x 20 screws. Tighten to a torque of 10 Nm 1
(7.5 lbf.ft). 2
When installing the new cylinder spacer flange in
older machine versions, check the filter base/
carburetor/flange/cylinder=~ssembly as follows:
M5 x 56 screws (1) and plugs 4133 122 6900 (2)
must be used with the new spacer flange. The
spacer flange must be mounted to the cylinder with
M5 x 25 screws (3) and A 5.3 washers (4).
)Technical Information 03.95 - Page 3
6XPPDU\
Item Part Name Original New Rem.
version version
1 Cylinder 4133 022 0500 4133 020 1250 1)
Spline screw
IS-M5 x 16 (2x) 9022 341 0980 --- 2)
Spline screw
2 IS-M5 x 20 (2x) --- 9022 371 1020
All other parts as before
Gasket 4227 129 0900 4227 129 0901 3)
Spacer flange, complete; 4133 120 2202 --- 1)
including items 3 to 6:
3 Spacer flange -*- 4133 121 1602
Spline screw
4 IS-M5 x 56 (2x)
9007 319 1121 9007 319 1121
5 Hex. nut M 5 (2x) 9210 261 0700 9210 261 0700
6 Plug (2x) 4133 122 6900 4133 122 6900
Modification to be introduced from machine number X 31 409 901
5HPDUNV
1) Original version of part no longer available from factory
2) Original version of part remains available as spare part
3) Original version of part will be supplied from factory only until existing stocks are exhausted
Last Technical Information on model BG 72: 28.92
Waiblingen, June 19, 1995 Andreas Stihl - D1/MTK-al
1995 Andreas Stihl Technical Documentation Page 2 of 3
Page 3 of 3
Extracted from the manufacturer's 2012 service catalogue. Most of these PDFs embed fonts with a shifted character map, so the text above was recovered rather than copied — read it as a faithful but imperfect transcription, and treat the page image above each block as the authority where the two disagree — the figures exist only there, because they are vector drawings that text extraction cannot keep.