Sachs SA 340 Setup guide

c(SJ
SACHS -
RepairInstructions No.4075.8 E
$ACHS Snowmobile Engine
Type
SA340
.
340 SS (super sport)
370
~ Edition December 1969
FICHTEL&SACHS AG · 8720 SCHWEINFURT
. ·~·

CONTENTS
Preface . . . . . . . . . . . . . . . . . . . . . .
Installation dimensions for SACHS SA 340 and SA 340 SS
{with
solenoid-contro ll ed starter) .. . ... .. .. .
Installation dimensions for SACHS SA 340 and SA 340 SS
(with
inertia-pinion type star te r)
Installation dimensions for SACHS SA 370
Technical data
Repair tools and assembly jig
Taking down the engine
Work on individual parts . . .
SACHS spe cial extracting too l for crankshaft oil seals
(without dismantling the engine)
Changing crankshaft bearings .. . 0 •
Recoil star ter .. . .. . . . .. .. .
Flywheel
dynamo magneto centering t ool
Replacing the magneto housing or the flywheel
Carburettor . . . . 0 • • 0 • • • • • • • • •
Decarbonizing the exhaust muff l er, cylinder and cylinder he ad
Asse mbling the engine . . . . . . .. . o • •••••
Test -runn ing and running-in the engine ... . . . . .
Engine with BOSCH solenoid-controlled starter (Type DD)
Engine with BOSCH inertia-pinion type starter (Type DG)
Operation, maintenance and lubrication of electric s tarters
Starter faults o o o o o •••• o ••• o • • •• • •
Instructions and wiring d i agram for dynamo magn e to 12 V 40 W .
In s tructions and wiring diagram for dynamo magn et o 12 V 75 W .
In s tructions and wiring diagram for dynamo magneto 12 V 40 Wand
BOSCH so lenoid -controlled star t er ( Type DD) . . . ...... .
Instructions and w iring diagram for dynamo magneto 12 V 75 Wand
BOSCH solenoid-controlled starter (Type DD) . . . . . . . . . .
In struct i on s and wiring di agram fo r dynamo magneto 12 V 75 Wand
BOSCH in er tia-pinion type starter (Type DG )
Laying-up the e ngin e .. o •• ••
Lubrication and maint e nanc e chart .
Tightening torques for bolt s and nuts
Repair dimensions
Engine fault s . .. . ... . . . .
Page
2
Folding sheet
Folding sheet
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Foldi ng sheet
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PREFACE
This manual is designed to give dealers and their staff all
guidance and information necessary to enable them to provide
an efficient repair and maintenance service, but it is in no way
intended as a substitute for the practical and theoretical
training available to personnel at our customer service training
school.
It will be found useful as a ready reference in day-to-day
workshop practice. Our illustrated Spare Parts List, containing
details of the various units and their construction , will also be
found helpfu l when used in conjunction with this booklet.
Of course, good maintenance and repair work and efficient
service
to customers call for good equipment, a well fitted-out
workshop, and trained personnel.
.
Dealers are requested to make this manual and all SACHS
circulars containing technical information and modifications
available to every individual responsible for actual servicing.
It is emphasized that all information of this nature is intended
for u,se in the workshops and not for office filing.
We hope that this manual will be of real practical assistance
to all our dealers, agents and associates.
2
FICHTEL & SACHS AG
SCHWEINFURT
Service Dept.

Technical Data
D es cripti on: SACHS SA 340 I SAC HS SA 340 SS (super sport) I SA CHS SA 370
Type: Fan-cooled single-cylinder two-stroke gasoline engine
Direction of rotation: Anti-clockwise as seen on th e output sh aft of th e engine
Swept capaci ty: 3
36 cc (20.503 cu i n. ) I 368 cc ( 22 .4 55 cu in .)
Bore:
rJ; 75 .5 mm ( 2.972 in.)
rJ; 79 mm (3.1 10 in. )
~
'·
Stroke :
75 mm (2.77 9 in .)
Comp ression ratio:
9 I 11
I 9.7
I I 23.5
HP (DIN) at 5250 rpm
I with
ca rburett or HR - 18 A
Ou tp ut:
22 HP ( DIN ) at 525 0 rpm
26 HP (DIN) at 6000 rpm I 24.5
HP ( DI N) at 52 50 rpm
i wi
th ca rbu re tt or HD- 13 A
Ignition:
BOSC H fl yw heel magneto
12 V
40Wor 12 V75 W
Ignition
ti ming: stopped engine : 0.2...0
.4 mm
running engine: 4.1...4.7 mm
before TDC (0.00 79...0 .0 1 57 in.l
before
TDC ( 0. 1 968 . .. 0 .2283 in.
Contact breaker
gap: 0.4 ± 0. 05 mm (0 . 016 ± 0.002 in.)
12 V
40 W equipment : st op p ed engine 32 ... 36 mm
( 1. 2598 ... 1.4 173 in .l
Pol e shoe gap:
running engine 14 ... 18 mm
( 0.5511 ... 0.7087 in.
12 V 75 W equipment: sto pped engine 25 ... 29 mm
(0.9842...1. 1417 in.l
• running engine 7...
11 mm (0.2756...0 .4331 in.
Spark plug: BOSCH M
240 T 1 I BOSCH M
260 T 1 I BOSCH M 240 T 1
Tl
LLO T SO N diaphr agm car burettor
Carburettor:
HD - 13 A 1 'h'' (38.10 mm dia .) I
HR-1 8 A 1' 11•" ( 30. 16 mm dia. )
Main jet =1 turn open I
~
Main j et =1 1f, turn open
Carburettor setting : Idling j
et =1 tu rn open
Idl in g jet =1 t urn open
Air
cleaner:
Intake si lencer
Exhaust muffler: Swirl-type exhaust silencer
Recoil starter
Method
of starting:
,~·
on request solenoid-controlled starter 12 V 0. 4 H P.
or inerti a-p i ni on type starter 12 V- 0.4 HP.
necessary ba ttery }2 Vo lt 32 .., 38 Ah
w Engine lubricati
on:
Two -stroke mixture mixed 25 : 1 ra ti o

REPAIR TOOLS AND ASSEMBLY JIG
'{J 14,6
~
Cj
· ~ -
2 3 4
'{J 21, 1
. ..;
,._
'fJ21 ,9
9
6
12
13
14
~
17
11
15
16
F & SI..071:22/2
4

for engine
tn
lllustr.
tn
Part number D
es cription 0 0 0
No.
.... ....
,.._
"" "" ""
<( <( <(
tn tn tn
IRepa
ir too ls
1 0276 065101
Gudgeon pin ex tractor
X X X
2 1447 020 000.8 I
nsert for gu dgeon pin extra ctor
X X X
3 1449
011 000.8 Locating pin
for piston
X X X
4 0976 088 100 Protective
cap, 14 mm dia . bore
X X X
5 0976
111 100 Retaining lever X X X
6 0276161
101 Oil seal extractor
X X X
0276 164 102 Ex tra ctor h ook 4 mm (1 piece ) X X X
1476 012 000 .8 Thrust b ear ing a·ssy.,
spare part for 0276161 101
X X X
7 0977 063105 Extractor for magn eto fly whe el M 50x1 X X X
8 0276 135 000
Ti ming gauge for spark advanc e X X X
9 1376 020 000.8 Revolu
ti on counter
X X X
10 0276 170 000 To-
rque key X X X
11
1476 013 000.8 E
xt ractor s leeve assy .,
cons isting of : X X X
1476 011 000.8 ex tr a ctor sleeve
1440 027 001.8 h exagon head bolt
1476 012 000.8 thrust bearing assy.
12 1447 009 000.8 Clamping ring,
I. D. 58 mm X X X
13 1476 014 024.8
Ex t ractor she lls for inne r races
of roll er beari n gs NJ 306 C3 NA X X X
14 1476 014 000.8 Ex
tractor she l ls for bearing bushing
(recoil
st arter) . . . . . . . X X X
15 1447 009
001 .8
Clampin g ring, I. D. 85.5 mm X X X
16 1476 014 023.8 E
xtr actor she ll s f or g roo ved ball
bea ring 6306 C3 X X X
Assembly jig
17 0276
081 000
Clamping base
X X X
18 0276 082 000 Swi
ve l unit X X X
19 0276 085 005 S
ets cr ew
X X X
20 0977 0
41 000 Mounting
plate
X X X
I I
I I
5

TAKING DOWN THE ENGINE
Remove all conn ections from e ngine to frame and unit (cables, ele ctric conne ct ions
etc .).
U
nscrew def l ector on cyl inder on SACH S SA 340 and SA 370, if th ere is on e.
Un screw exhaust mu ffl er, i .e . man ifold and bracket.
Rem
ove the engine and cl ean t horo u ghly be f ore taking down.
When giv i ng the engine a ge n eral ove rhaul, co mp onents shou ld be removed in t he
se quence in dicated.
Fi g. 1
Fig. 2
6
Exhaust muffler , carbur e ttor and
electric starter
Fig. 1
Scr ew dow n engine on the as-
sembly jig w ith 3_ hexagon hecid
bolts M l 0 x 40, as shown in the
adjoining il lust ra t io n.
Pull
off i mpu lse pi pe (4).
Remove
int ake silen cer (3) and
carburettor (2) .
Rem
ov e r ns .ul ating sleeves and
insulat i ng flan ge .
Rem
ove fl an ge {l ) only if neces-
sary.
Unsc
rew ele ct ric star te r (5).
Re coil starter, s tarter hub and fan
Fig. 2
Detach reco il starte r.
Un lock nut in th e star t er hub (2) .
Hold sta·rter h ub wi th r etai ni ng
lev er (3, repair t oo l no. 5), un-
screw the n ut and re mov e starter
hub with spr ing ri ng and washer.
Rem ove 2 cylin dri cal pins and
s pace r.
Unscrew
fan (l) and remo ve
ga sket.

Cover plate and fan housing
Fig. 3
Unscrew fixing clip for ignition
lead (only wit h 40 W equipm ent)
and cover (l ).
Detach leads at t erm inal s 1, 2
and 3 of the terminal box (6) and
re mo ve fa n housing (3) .
Note:
Re mo ve _ cover flange s on fan
housing for electric st arter c on-
nection , if fitted.
When re mo vi ng the fan housin g,
pull the insu lating ho se (5) with
l ead th rough .
T
ake car e of c! o we l tub es.
Note: . ·
Rem ove short-circuiti ng button
on ly if necessary.
Re
mov e·ru bber cap (2) and sh ort -
circuit ing bu tton. ·
Detach
short-cir c~itin g . le ad f rom
in_s ulator . :
Re
mount part s in rev er se o rd er.
Magneto flywheel
Fig. 4
F it prot e ct ive cap (re pair t oo l no.
. 4) to threaded end of crankshaft.
F
it ret aini ng lever (l , repa ir to ol
no. 5) to magne to flywheel and
pull off the f ly wheel by means of
th e ex tra ctor (2, repair to ol
no . 7 ).
Labyrinth ring and armature
ba se plate
Fig. 5
Un screw la b yrinth rin g (5).
On engine wit h 40 W eq uipm ent,
pull
ignition lead with spri ng out
of the spark plug t er minal (6),
pull off rub b er sleeve (1) a nd
rubber c ap (2) and screw out the
ignition l ead socket.
Un screw armature base plat e (4)
and rem ove it to ge th er w ith igni-
tion le ad (on ly w ith 40 W eq uip-
ment) and insul ating tub e (w ith
l
ead ).
Remove
Woodr uff key .
F &SL.-075: 22
Fi g. 3
Fig. 4
Fig. 5
7

Fig. 6
Use only genuine SACHS spares.
8
Cylinder head, cylinder and
piston
Fig. 6
Unscrew cylinder head and cy-
linder.
On SACHS SA 340 SS, remove
cylinder head gasket.
Pull off cylinder without twisting.
(
Dang er of breaking piston
rings .)
Remove
cylinder flange gaske t.
Note:
The cylinder can be rebored
twice. Use appropriate piston
(see Spare Parts List).
A
cylinder wit h chromium -pla ted
piston bearing surface cannot
be rebored.
Place cylinder on hom e- made
s lott ed wooden board (1 ).
Cov er the crankcase, take out
the two wire circlips. If neces-
sar y, force out gudgeon pin with
gudgeon pin extractor (3, repair
tool no. 1} and insert (2, repair
tool no. 2) .
When fitting the steel band, care
should be taken to ensure that
the piston rings are in their groo -
ves . (Danger of breaking piston
rings.)
Remove
slotted wood en board.
Crankcase and crankshaft
Fig. 7
Unscrew 6 hexagon socket head
screws from crankcase.
Unscrew h exago n hea d bolt {4,
Fig. 3) and sp lit crankcase by
t apping the crankcase ha lf pow -
er takeoff side s li ghtly with a
rubber hammer.
Remove crankcase half power
tak eoff side and gasket. Take
care of dowel tubes.
Unscrew screwed nippl e {1} and
oil drain cock (2).
Uns crew crankcase half magneto
side from the as se mbly jig and
he at it to 100 ... 150°C (212...302 °
F) for removing the crankshaft
(grooved ball bearing) .
Clean all parts thoroughly, check
for wear and r ep lace when ne -
cessary.

WORK ON INDIVIDUAL PARTS
SACHS special extracting tool for crankshaft oil seals
(without dismantling the engine)
FICHT EL & SACHS AG have deve loped a special extra cting tool by means of which
da mag ed oil sea ls can be repla ced w ithout a major disasse mbly of the engi ne being
necessary.
Engine t
roubles caus ed by le ak ing or damaged oil seals can thus be remedied 1n a
relatively sh ort time.
When replacing oil seal s, the foll owing poin ts sh ould be borne in m ind:
Extracting oil seals
Fig. 8
Before ext racting the oil seal be
sure
to record installation dimen-
si on x, o or y, in ord er that th e
new
oil seal can be fi tted to the
same
dimension.
Note:
If the correct installation dim en-
s
ion is not adhered to , en gi ne
troubles may occur by closed oi l
bor es in th e erankcase or by ro-
tati ng parts moving again sto th er
parts.
Fi g. 9
If the oil se al is locked t owards
o ut s ide by means of a collar (a)
or other locking element, it can-
not be extra c ted .
F ig. 8
Fig. 9
F l S 077: l
Q
9

F & S 400:58
Fi g. 10
Fi9. 11
Fitting the oil seal
Fi g. 12
10
F ig. 10
Place the extracting t ool in po-
sition in such a way tha t the tw o
ho oks (4) gr ip be hind the sheet
steel rim of
th e o il seal. Pre- te n-
si
on the two legs (2) even ly w ith
cylinder head screws {1 ), taking
care that shaft (5) and t hr ust
sc
rew (3) are in a lign ment.
Screw in
thru st s crew and extra ct
oil seal.
Fig. 11
If the ga p betwee n sha ft and
sheet steel rim of oil seal is t oo
narro w and the extracting t ool
cann ot c ompl ete ly be pl aced in
position, take off one leg of the
ext
racting tool and ins ert bot h
hooks (l) in inc lin ed posit io n.
Rem ount leg and ext ract oil s eal
as described unde r Fi g. l 0.
Note :
If th e oil seal ha s got stuck ( oxi -
dation ), the sheet steel rim m ay
break. There for e it is advisab le
to knock
th e oiI seaI out of its
forc e fi t by means of a tub e.
Fig. 12
B ef ore fitt ing the o il seal, fil l the
s
pace a· ro und th e tens ion spri ng
wi th a littl e heat-resis ti ng grease
and li gh tly sm ear the sea lin g l ip.
To pro te ct the sea ling lip of the
oil seal
fro m damag e caused by
sh arp edges on th e shaft , use
sh ell sleeve. If necessary, p ut
sm ooth ad h es ive tap e arou nd
sh arp e dg es .
Place oil seal in pos
it io n a nd
pr ess it in by means of a su it ab le
tub e, taking care of exact inst al -
lation dimens ion x, o and y
(F
ig. 8).
The oil se al must not be tilted
when bei ng pressed in.

Changing crankshaft bearings
H eat crankcase hal ves to about 100...150 °C (212 ... 302 ° F). Remo ve outer races of
bearings and cra n kshaf t oils seals.
In sert n ew outer races of roller bearings in to the wa rm crankcase halves until they
strike a stop . Press in oil sea ls (with sealing li ps inwards) until t hey are flush.
Pr
ess in new grooved ball bearings into the warm crankcase halves on the magneto
side until they strike a sto p. Press in crankshaft oil seals until flush on ly after the crank-
case halves have been screwed together.
Removal of inner races of roller
bearings and grooved ball bear-
ing
Fig. 13
Pull off inner race (1) and groov-
ed ba ll bearing (4) by means of
the appropr iate extractor shells
(9 and 6), clamping rings (8 and
7) a nd wi thdrawal tool (10, re-
pair tool n o. 11 to 16).
Remove spacers (3) and compen-
sat ing was h ers (2).
F&S 1..075:25
Fi g. 13
11

Fig. 14
Gauging axial play of crankshaft
Fi g. 14
Permissible axial play 0.1 ... 0.2
mm (0.0039...0.0079 in.).
Example:
Inse rt inner race of
cylindrical roller bearing
into outer race.
C rankcase po wer t akeoff
si de : seali ng s urfac e
(with
gas ket) to inner
ra · ce of bear ing 40.60 mm
Crankcase magneto
s ide: seali ng su rface to
inn erraceofbearing + 39. 50 mm
C
rankcase gap 80.10 mm
Dimension of
crankshaft, measured
over both cr ank webs,
with a 5 mm thick
s
pac er on power
takeoff and magneto
side - 79.00 mm
Axial
play
Permissible ax ia l
play
Difference
to be t aken up
1.10 mm
-0.20 mm
0.90 mm
The diff ere nc e of 0.90 mm is tak en up by inser ting shims (2, Fig. 13) be tw ee n the sp ac er
(3, Fig.
13 ) and the inner rac e of the cylindrica l ro ll e r bearin g (1, Fig. 13) on the cr ank -
pin power ta keoff si de.
Fitting the inner race of the cylindrical roller bearing
Wh en fitting the inner rac e of the cylindrical roller bea ri ng ( do not forg et spacers 3,
Fig .
13 on crankpin pow er tak eo ff side), an intermediate plate (5, Fig. 13 ) sho ul d a l-
way s be p os itioned be tw ee n the two crank we bs . This plat e must be of such a si ze
that it ca n be s upported at both ends, there by pe rmitt i ng t he crank s haft to li e freely
in
po sition.
Ne
ver c lam p the crankshaft in a vic e at a crankpin or at the webs and neve r try to fit
the inner race by striking it. Th is will crush th e we bs and re nder the cra · nkshaft
uns erviceable .
12

Recoil starte r
The recoi l starter is ava i lab le for cl ockw i se or a nt i-c lockwise starting direction.
It c an also be subseq uently converted for the other star ting direction.
The illust ration bel ow shows the two starti ng directions.
Fi g. 15
Recoil s tarter for engine running
in clockwise direction
Recoil starter for eng i ne ru nning
in anti-c l ockwi se direct i on
(as seen on the power take-off side of the crankshaft)
Dismantling
Fi g. 16
Take out brake spring (5), shims,
spring ring , friction plat e (3),
wa s her 0.1 mm (0.0039 in.) th i ck
and star t er paw ls (1 and 4).
S
crew off labyri nth ring (2) .
Fi g. 16 F
&S4 07 l :JJ
13

F &$4071:34
Fig. 18
4
F & Sl.071:36
Fig. 19
14
Fi g. 17
Pull out starter cord approx.
50 em (19 in.) and hold pulley
with home-made retaining clip
(1 ). '!. '
T ake clamping ring with clamp-
ing taper out of starter handle.
Withdraw clamping taper from
clamping ring and detach cord.
Remove clamping ring and star-
ter hand le with stop from cord.
Remove re taining clip (1) and let
sta· rter cord run back completely.
Carefully take out pull ey with oil
spring, taking car e n ot to l et coil
spring jump out.
Take care of disc (3, Fig. 19).
Remove
cord from pulley.
Fi g. 18
Rai.se spri ng end to take out coil
spn ng.
Hold coil spring firmly with both
thumbs (s ee illustration) and , by
raising each thumb , let out
spring on alternate sides.
Note :
R eplace bu sh (2, Fig. 20) only if
necessary, us ing the extractor
she ll s (repa ir tool no. 14).
Take car e of tol era nce rin g in
bush (2, Fig. 2
0) .
Assembly
Fig. 19
Bef ore asse mblin g, grease coil
s pring with A e ro - SH E LL grease
14
and fi ll the 41ubricating groo-
ves in the pulley with the same
lubr icant.
Insert
coil spr ing with end of
s prin g (2) in stud (1) and fit in co il
by coil.
Ens ur e that the co il spring li es
fl at and even.
Note :
F or clockwise starti ng dire ct ion,
insert coil spri ng as shown in
illustrati on, for anti -c lo ckwise
directi on in sert coil s pring r E;,y er-
se ly . • '-i ·' .~ ... -"'

Fi g. 20
Before inserting pulley, stick disc
(3, Fig. 19) 0.8 mm thick (0.032 in.)
with a little grease into recess of
pulley.
Fit pulley on to bearing bolt and
insert end of spring (4, Fig . 19)
at stud (1 ).
Tension pulley/coil sp ring in di-
rection
of cord exit until stop is
encountered .
Release coil spring
approx.
1h ...1
turn until the recess
for the sol-
dering nipple
in the pulley rests
near the cord duct of the hous-
ing.
Again hold
the pulley firmly with
home-
made retaining clip (1,
Fig. 21 ).
Pull the starter cord through a
rag soaked with SAE-1 0 oil be-
fore assembling.
Fig. 21
Note:
When converting starting direc-
tion, reposition cord
guide (2)
also.
Fit starter handle with stop and
clamping ring on to cord.
Lay
starter cord around clamp-
ing
tap er and pull it into clamp-
ing ring.
Pull clamping ring into s tart er
handle and let starter cord run
back.
Fig. 22
Screw labyrinth ring (2) tight.
Lubricate
starter pawl bed and
starter pa wls lightly with SAE -1 0
oil.
Fit s tart er pawls (1 and 4).
Th e OJJen side of the starte 'r pa wl
seoti f;l g and the long side of the
starter pawl face in starting di-
rection.
Fit washer 0.1 mm (0.0039 in .)
thick, friction
plat e (3), spring
ring
and s him s as required.
In sert brake spring (5).
F &Sl..071:37
Fig. 20
F & 5 407 1:31..
Fi g. 21
F &St..071 :33
Fig. 22
('\ ..
After mounting the br ake spring, the friction pla Je sho ul d h ave a n ax ia l pl ay of
0.1...0.2 mm (0.0039 ...0.0079 in.). . ,
Correct this play by putting shims under the
brake S!"ring.
15

Replacing the magneto housing or the flywheel
2
F' &S l.OSl..:tOS
Fi g. 24
F& Sl.OS/.:106
Fi g. 25
Note:
Fi g. 24
Scr ew out 4 recessed head screws
in fly wheel.
Sc rew in 4 hexagon head screws
(1) from other side (with equip-
ments without gear ring for elec-
tric starter the 4 staybolts must
be removed before) and press
out fl ywheel (2).
Fi g. 25
Unscr ew retaining strip (2) and
take out cam (1 ).
Fill ann ular groove (3) with heat -
resisting grease and grease cam
support in flywh eel.
Insert cam (1 ), fit reta ining str ip
(2) and sc rew tight with 3 cylin-
der head screws M 4 x 5 and
washers .
Take retain ing ring (5), flyw ei ght
(4) and thru st ring below off
b earing pin.
Grease bearing pin and bearing
surface for flyweight in flywh ee l
with heat -resisting grease .
Fit
thrust washer (0.3 mm thic k)
on
bearing pin, hang spring (6)
into place in flyweight .
Fit fly
weig ht on bearing pin
(must e
ngage with cam) and se -
cur e with reta ining ring (5).
Cam and fly weight mu st always
be free-mov ing.
On eq uipm e nt s with gear ring for electric st arter th ere are two marking s in the
magneto housing : "4 0x" (for 40 W eq uipm ent) and "75x" (for 75 W equ i pme nt).
The fly whe el should be fitted in such a way that the bo res in the fl ywh ee l are per-
fectly in line with the bor es in the hou si ng.
On engine witho ut el ec tric s tart er, fit appropriat e m ag neto ho using ( see Spare P arts
Li st) according to e quipm ent (40 or 75 W ) in such a way that the bores in the housing
are perfectly in line with the bor es in the fl ywheel.
Pr ess in flywheel.
De grease 4 Philips screws M 6 x 10 with Tri, app ly LOCTITE to the m a nd screw them in.
Tight ening t orque 0.9... 1.1 kpm (6.5...7.9 ft. lb. ).
18

Carburettor
The typ e of carburettor, the jet size and the j et adjustm~nt are d~termin ed by means
of t es ts in the fa ctory . Th e adj u stment determin ed in th1s way g1ves the bes t results,
and it is therefore not advisable to alter it.
No a l teration of t he carburett or setting should be made as long as the eng ine turr~s
over quie tly and smoo thly when idling, accelerates steadily when the_ throt tle IS
opened, and gives its full output at full rev s without choking. )f the eng1ne p~unds
or runs unevenly, or the exhaust gas is black, the mixture is too nch. Repeat ed sp 1tt1n g
or cough i ng, or backfiring with a blue flame stabb ing from the carburettor coupled
with difficult starti n g, indica t es that the mixture is too w eak.
When running with the cor re ct carb ur ettor adjustment , a clean a ir filter and a suitable
spark ing plug wit h t he co rrect ther mal val u e, the insula tor of the sparking plug should
be brown in colour . Soo ty or wet plugs indicate rich mixture, whereas white ins ulator
po ints to the mixture being too we ak.
Special care sho ul d be taken to ens ure that the carburettor setting is never too low,
as at low throttle ins ufficient lubricant w ill be conveyed to the moving parts of the
e ng ine. With a two-stroke en gine the carbur et tor setting should a l wa ys be sufficient
to provide adequate lubrication.
Cor rect c arb ur ettor se tting will h elp to ensur e economic and trouble-free r unning of
t he engine.
Adjusting the carburettor for special climatic conditions
When using the engine at a l titudes above 1000 metres (3280 ft.), adjustments of the
carburettor setting will be required. As the air density is reduced at high altitudes, the
s upply of gasoli ne to the c arburetto r shou ld be restricted by changing the main jet.
Starting
On Tillotson diaphragm carbure tt ors the choke is i ncorporated in the carburettor
itself.
The choke should be u sed to facilitate starting from cold. It s hould not be used for
s ta rting when t he engine is warm and it should be par tially or fu ll y c losed only for
s tarting the cold e ngine.
Wh en the choke is cl osed, a higher vacuum is caused in the mixing chamber , so that a
richer fuel/air mixture is obtained. Once the engine has started, the choke should be
s lowly opened .
Th e Tillotson diap hragm carb u rettor can function in any position. The HR-8 A type a nd
the HR- 18 A type have two diaphragms , the HD-7 A type and the HD-13 A type have
three diaphragms : a contr ol diaphragm for proportioning the fuel feed to the engi ne
and a pump diaphragm (HD-7 A a nd HD-13 A have two pump diaphragms) for
drawing the fuel from the tank.
Carburettor adjustment
The Tillot son carburettor is the first carburettor u sed for SACHS engines which has
adjustable jets. If engine troubles occur and the jets have to be readjusted, the fo llow-
ing points sho uld be no ted:
1. To adjust the ca rb ur ettor correctly for · maximum output (full load ), the en gine
sho uld be thoroughly warmed up.
2. W ith
adjustable jets, car e sho uld be taken not to use too lean a fue l/ air mixture
(see a l so page 28) .
3.
The adj usting screws for t he jets mu st n ev er be screwed too ti ghtly to the right
(i.e. clos ed) in the jet s eat, as this wi ll deform the sea t.
4.
The main jet is marked "H" and the idling jet is marked "L" on the carb u rettor
housing.
19

Tillotson diaphragm carburettor
Fig. 26
l Hose nipp le
2
Fu el pump body
3 Fu e l pump d ia ph ragm
3A In let valve on pump
diaphragm
3B Outl et valve o n pump
diaphragm
4 Fue l pump gaske t
5
Diaphragm ho using gasket
6
Con t ro l chambe r
7 Adjus
ting screw for
idling jet
8 I
mpu l se passage
9 Idling jet or ifi ce
20
l OA I dling outl et passag e
lOB By-pass passa ge
ll Butte rf ly va l ve
12 Ma in je t orifice
13 Carbu ret tor ho using
14 Thr
oa t of co rbur e tt or
(v e nturi)
15 Mai n fu el outlet
16 Choke
17 Fu el passage from pu mp
to co n trol c hamb er
18 Inl
et needle a nd sea t
l8A Copper sea l
19 Ad j usting sc r ew lor ma in j et
H. SI.JO 1!.1
20 I nle t c ompr ession spring
21 Inlet co n tro l l eve r
22
23
24
25
26
27
28
29
30
31
32
Pivot
pin
Vent hole
Diaph r ag m hou si ng
Di ap h ragm
Air chamber
Filter gas ket
Fu el st rai ner
Filt er h ousing screw
Fuel chamber
Pul sa ti on cha m ber
Fuel filt er housing