JLO L/RM252 User manual

JLO L/RM252 ENGINE MECHANICS HANDBOOK
Table of Contents – Page 1 of 1
PREFACE
TECHNICAL DATA
OPERATING - AND MAINTENANCE INSTRUCTIONS
A. BEFORE STARTING
B. SERVICE AND MAINTENANCE
C. ADDITIONAL INSTRUCTIONS
D. GENERAL TROUBLE SHOOTING
ASSEMBLY GROUP 1
RECOIL STARTER
ASSEMBLY GROUP 2
FLYWHEEL, IGNITION SYSTEMS
ASSEMBLY GROUP 3
TIMING PROCEDURE
ASSEMBLY GROUP 4
SPEED CONTROL - RM 252 FLYBALL GOVERNOR
ADJUSTMENT INSTRUCTIONS - MECHANICAL
SPEED CONTROL--L 252 TOP SPEED LIMITER
ASSEMBLY GROUP 5
CARBURETTOR, CARBURETTOR DATA
ASSEMBLY GROUP 6
PISTON, CYLINDER
ASSEMBLY GROUP 7
CRANKCASE,CRANKSHAFT-RM 252
CRANKCASE , CRANKSHAFT - L252
TABLE OF SPECIFICATION

MECHANIC'S HANDBOOK
L/RM 252

MOTOR
SERVICE
U
7
5
1
1
4
4

CONTENTS
General vic emblof engine ass
Table
of contents
Preface
Technical data
Operating and maintenance instructions
Assembly group 1recoil starter
2flywheel,ignitionsystems
3 timingprocedure
4 speed control
RM 252 flyball governor
L 252 top speed limiter
5 carburettor, carburettordata
6piston,cylinder
7crankcase,crankshaft
RM 252
L 252
Table
of specification
Notes
Index of sales offices
Page
1
2
3
4
5- 6
7- 8
9-10
11-12
13-16
17-18
19-20
21-22
23-24
25-26
27-28
29
30

This Mechanic's Handbook contains comprehensive inform-
ation to properly operate, service, and repairJLO en-
gine models
L 252 and RM 252.
The repair procedures are described in detail and are
supplemented by useful illustrations.
1. Each assembly group is subdivided into DISASSEMBLY
and ASSEMBLY.
The illustration numbers shown in the general view
on page
1 refer to the individual assembly groups
in the procedure section.
2. When ordering replacement parts, please refer to
the pertinent spare parts list to determine the
correct part number. If the required spare part
cannot be identified, please describe the part and
state engine model and serial number (shown on
name plate) on your order form.
3. In case of a complete engine overhaul, please do
not try to save money by re-using worn or defec-
tive parts. It is always more sensible to replace
one part too many than to re-use a part which
condition is doubtful. When repairing an engine
which
is in poor condition, please use available
shortblocks rather than repairing the engine with
individual parts. This and the use of JLO sub-
assembled repair kits will help to save time and
money.
The part numbers and exact descriptions
of short-
blocks and repair kits may be foundat the end of
the spare parts list.
4. Always use genuine JLO spare parts!
5. To secure certain screws or nuts, a thread locking
compound
is used. We recommend to use "Loctite
249", "Casco 184" or equivalent.
Edition
10/86
3

L/RM 252
Type
Piston displacement
Stroke
Bore
Compression ratio
247 cm³ (15.057 in³)
66 mm (2.598")
69 nun (2.7165")
7:1
CHAMPION BOSCHBERU
L86C, L87YC W7AC 175/14C(Heatvalue145-225)
0.5 mm (0.020")
M 14x1.25 - 12.7 mm long
2.8 - 3.2 mm (0.110" to 0.126")
Spark plug
Spark plug gap
Sparkplugthread
Timing BTDC
Breaker point gap 0.3
- 0.4 mm (0.012" to 0.016")
Minimum Maximum
Ignition system 12 Volt/40Watts
primary resistance
internal ignition coil, 1.60
Ohms
5,300 Ohms
N/A
2 .00 ohms
5,800 Ohms
internal ignition coil,
secondary resistance
internal ignition
generating coil
Ignition system 12 Volt 75/98Watts
external ignition coil,
primary resistance
0.80 Ohms
7,800 Ohms
0 .90 ohms
9,200 Ohms
external ignition coil,
secondary resistance
internal ignition
generating coil
(bottom coil with black wire) 3.0 Ohms
0.43 Ohms
3.7 ohms
0.53 Ohms
lighting coil (12Volt 75 Watts)
(with yellow and yellow/black wire)
lighting coil 12Volt 23 Watts
(top coilwith green and green/black
wire)
condenser 0.24
0.20 mm (.008")
0.30
0.40 mm (.016")air gap, coil to flywheel
Fuel Mixture ratio (2%)
Regular fuel or regular lead-free fuel
Important:
During initial break-in period(approx. 20 hours)
use fuel/oil mixture ratio of 25:1 (4%)
Use special two-stroke oil,e.g.
CASTROL SUPER TT; ARAL SUPER 2T; ESSO (EXXON)
AQUAGLIDE, etc.
If not available, use oil SAE 30 or 40or known brand
Lubrication oil
Locking compound
Sealing compound
LOCTITE No. 241 / CASCO No. 148
b
4

Operating- and Maintenance Instructions
A. Before starting
1. Refueling
Mixtureratio-please see TechnicalData
2. Engine
Check that cooling fins of cylinder and air holesare free fromdirt to prevent over-
heating of theengine.
3. Air filter:
Be sure that all filter connections (clamps)aretight.
Oil bath filter:
Checkoillevel, refill if necessary.
4. Starting
4.1 Coldengine
Shift throttlelever into 'RUN' position. Open fuel tap Close starter throttle
Depress tickler untilfuel emerges from carburettor.Pull recoil starter firmlyuntil
engine starts. slowly return starter handle. If engine does not start. depress tickler
again. As soon as engine runs, open starterthrottle fullyindirectionof arrow. The flyball
governor automaticallymaintainsthe engine speed.
4.2. Warm engine
Same as 4.1, but do not depress tickler Close starter throttle if engine does
not start.
5. Stopping
5.1 For shortbreaks:
Shift throttlelever "STOP".
Close fuel tap shift throttle lever "STOP".
5.2
Forlongerbreaks:
B. Service and Maintenance
Servicing Work
Bolts andnuts and other connections
Check tightness,retighten if necessary
Ignition
Chock breaker point gapand ignition timing
Spark plug
Check spark plug gap andadjust if necessary
Remove depositsor replaceplug if necessary
Carburetor
Clean carburettorandfuel filter. also tankif necessary
Exhaust
Check
for carbondeposits.
Clean if necessary eventuallyburnout
Piston,combustionchamber,
andcylindertransfer
ports
Cleanfromcarbondeposits
Mechanical
flyball governor maintanance free
Corrosion for engines to be temporarilly stored
Use 50 cm JLO Corroilte M, orderno. 002.75.001.000, andobserve the instruction included.
5

C Additional Instructions
1. Alr Intake filter
Keepdustanddirtoutoftheengine to avoid prematurewear. If engineisoperatedlndu-
sty or dirty environment,theair filtermay haveto becleanedinshort intervals.
1.1 Paper elementfilter:Blow out with air against normaldirection of airflow.Replace wetor
very dirtycartridges.
1.2 Oilbath filter:
Changeoil (fillingqty. 160-180cm³SAE 30) and observe indicatedmark!
D. General Trouble Shooting
Possiblecause:
1. Englnedoesnotstart
1.1Fueltap closed
1.2 No fuel intank
1.3 Clogged fuel filterincarburettor or
1.4Engine over-choked(flooded)
tap of fuel tank or fuelhose
1.5 Spark plugfouled
1.6 Main carburettor jet plugged
1.7 Dirtycarburettor
1.8 Spark plugcap or ignitioncable
looseor damaged
Remedy:
Open fuel tap
Fill tank with clean, freshfuel/oilmixture
Cleanfilter, blow outdirt
Close fuel tap. Start engine several times.
Remove spark plug, clean anddry it. If
necessary, crank engine without spark plug.
Clean and regap sparkplug.Replaceif
necessary. (Plug typesee A Technical Data)
Clean
Clean
Retighten, resp. replace
2 Engine runs unevenly or ceasesto fire
2.1See1.5-1.8Seeabove 2.2Loosespark plug Tightenspark plug
3. Engine does not produce full power
3.1See1.5and1.6Seeabove 3.2 ChokestillclosedOpenchoke
3.3 DirtinfuelfilterandhosesClean
3.4 DirtyaircleanerormainjetClean
3.5 Exhaust and/or exhaustportin
3.6BowdencablemisadjustmentAdjust properly
cylinderclogged Removecarbondeposits
All otherfailureswhich require partial or completedismantling of theengineshould
always be taken care of byan approvedserviceshop.
Improperrepairingcan cause damages and lifts the claim toguarantee.
Usegenuine JLO spare partsonly.
CAUTION
Carriers of cardiacpacemakersshouldavoidtouchingcurrentcarryingparts of the
ignitionsystem.
6

Assembly group1
RECO I L STARTER
DISASSEMBLY
1.1. 1 Pull knot (1a)out of handle (2) and untie.
2 Allow rope (1) to retract slowly.
3 Remove nut (3) and parts (5,6,8,9) - (illustration I).
4 To prevent. the recoil spring from uncoiling (see illustration II), rotate rope
pulley (10) back and forthto disengage inner spring eye and carefully lift out
of housing (7).
5 Remove rope (1) from rope pulley (10).
NOTE :
Recoil spring (4) need not be removed from housing (7) unless it is broken.
6 To remove spring (4), take housing (7) in both hands, open side down, and hit
housing (7) on work bench or otherflat surface. Springwill dropout.
7 Clean and inspect all parts for damage and wear, and replace if necessary.
ASSEMBLY
NOTE: Note required direction ofrotation. See illustration III.
Old recoil spring (only if removed from housing during disassembly):
1.2. 1 Wind recoil spring (4) into housing (7). See illustration II.
2 Lubricate recoil spring (4) and rope pulley shaft (12) with some multi- purpose
grease.
New recoil spring - prewound:
3
4
5
6
7
8
9
10
11
12
13
14
15
Place recoil spring (4) in housing (7) and push with screwdriver down into
housing (7). Remove retaining wire with snipe nosed pliers.
The outer spring eye (4b) must be properly hooked around the retaining tab
(illustration III).
The clearance required between inner spring eye (4a) and rope pulley shaft must
be approx. 4 mm (.160 in.). If necessary, rebend spring eye (4a) (ill. III).
Lubricate recoil spring(4)and rope pulleyshaftwith some multi-purpose
grease.
Fit rope pulley (10) and carefully rotate it back and forth until it engages in
the inner springeye (4a).
Install parts no. 8,9,6,5, and 3 (illustration I).
Fit long end of torsion spring (8) into hole of rope pulley (10), pushing it
over pawl guide (11) (illustration IV).
Slip pawl (9) with smooth surface pointing upwards over pawl guide (11). Short
end of torsion spring (8) must fit into groove of pawl (9a) (illustration V).
Fit brake spring (6) to brake disk (5) as shown in illustr. V. Note position of
brake spring ends (6a) in relation to flat on one side of brake disk (arrow).
Position rope pulley (10) in relation to flat on pulley shaft (12) as shown in
illustr. V (arrow). Install brake disk (5) with brake spring (6) onto pulley
shaft (12). Flat in brake disk must match flat on pulley shaft. Fit hex. nut (3)
and torque to 6 Nm (4.4 ft/lbs).
Rotate rope pulley (10) against the recoil spring tension until it is tight and
hold firm (illustration VI).
Let rope pulley (10) now rotate backwards until hole in rope pulley (10a) and
rope guide in housing (7a) are in line.
Slide rope (1) throughhole in rope pulley (10a) and then through the rope guide
in the housing (7a).
Slide rope (1) through handle (2) and tie knot. Slowly return handle.
If the recoil starter has been properly assembled, the pawl (9) must move outward when
rope is pulled.

I 6
5
I
le 2
6a
Oa
10
7
11

Assembly group 2
FLYWHEEL, IGNITION SYSTEMS
Special JLO Tools
Flywheel puller (11) 444.31.843.100
DISASSEMBLY
2.1. 1
2
3
4
5
6
7
8
ASSEMBLY
2.2. 1
2
3
4
5
6
7
8
9
10
11
Remove screws (1) with lock washer (2) carrier(3).
Remove screws (4) with lock washer (5) andfan cover (6).
Remove hex. nut (7). spring washer (8), and flat washer (9).
To pull off flywheel (10) use puller (II).Unless magnetic flywheel (25) is defective
it need not be removed from fanwheel (10). To separate magnetic flywheel (25) from
fanwheel remove hex. nuts (24), lock washers (23). and screws (22).
NOTE :
Holes in magnetic flywheel are unevenly spaced, so flywheel will onlyfit in fanwheel
in one position.
Remove key (12),cam (13),spring (14), washer (15) , and pin (16).
Note or mark position of armature plate in crankcase. Remove screws (17), lock
washers (18),and flat washers (19). Remove armature plate (20).
Check coils, condenser, and breaker points, and replace if necessary. (For specifica-
tions, please referto page 4).
If engine is so equipped, remove external ignition coil (21).
Slightly lubricate wires withsilicon spray andfeed them-through their corresponding
grommets.
washers (19).
Install armature plate (20) and fasten with screws (17),lock washers (18),and flat
If engine is equipped witha 12 Volt, 75/23 Wattsignition system, the green and
green/black lead of the23 Watts coil must be connected.
(See wiring diagramon page 12).
Place thrust washer (15) and spring (14) on crankshaft. Install cam locating pin (16)
in its groove (16a).
NOTE :
Cam (13) has 2 grooves on the inner periphery. Each groove is marked with anarrow.
pointing to the clockwise rotation.(Groove"L"asshown in illustr.
If the engine isto runcounterclockwise, you must use the groove withthe arrow
II and III).
Position cam on crankshaft. Be sure pin (16) is properly seated in cam groove.
To properly set ignition timing, please referto timing section on page11/12.
Degrease crankshaft taper and mating taperin fanwheel (10).
Place key (12) in keyway on crankshaft. Inspect inside of magnetic flywheel to
be sure no foreign parts cling to magnets.
NOTE :
Fanwheel (10) has 2keyways. If the engine is to run counterclockwise, you must
use the keyway withthe arrowpointing to the clockwise rotation. (Keyway "L" as
shown in illustr. II) .
Place fanwheel (10) on crankshaft.Be sure key (12) is locatedin proper keyway.
To prevent water from getting into the ignition area through the unused keyway,
apply sealing compound (10a) to face of fanwheel hub as shown. Install flat
washer (9), spring washer (8), and hex. nut (7). Torque hex. nut (7) to 90-100
Nm. (65-75 ft/lbs).
Install fan cover (6) with lock washers (5) and screws (4).
Install carrier (3) with lock washers (2) andscrews (1).
9

25
15 14
clockwise \
cam
13
erclockwise rotation

Assembly group 3
PROCEDURE
Special JLO Tools
Timing gauge
(1) 441.31.875.000
Timing light (2) 000.15.330.000
TIMING DATA:
- EngineModel L/RM 252 -
TimingBTDC .110 - .126 inches (2.8 - 3.2 mm)
Breaker Point Gap .012 - .016 inches (0.3 - 0.4 mm)
Spark plug gap .020 inches (0.5 mm)
PREPARATIONS
3.1. 1 Screw timing gauge (1) into spark plug hole of cylinder head.
2 Connect one lead of timing light to engine ground, the other lead to
the disconnected wire of theignition system.
3 Bring piston into top dead center position.
BREAKER POINT GAP
4 Check breaker point gap with feeler gauge.
5 To adjust breaker point gap, loosen retaining screw
(4) and adjust to
specified gap by moving fixed part of point set (5).
6 Tighten retaining screw (4),and re-check gap.
IGNITION TIMING
NOTE
:
Breaker points mustbe adjusted to proper gap PRIOR to timing the engine.
7
8
9
10
11
Note reading
of timing gauge with the piston still in top dead center
position.
Turn crankshaft approx.
90° in opposite direction of normal direction
of rotation (away from TDC), then slowly turn flywheel towards TDC
until timing light (2) changes from dim to bright
or buzzer of timing
device changes loudness (timing point).
Note reading on timing gauge. The difference between the 2 readings
(step
7 and 9) is the timing in inches or mm, depending on calibration
of timing gauge, before TDC.
To change timing, loosen armature plate retaining screws (7) and rotate
plate in required direction.
NOTE
:
Rotating the armature plate in the direction of engine rotation will
retard the timing, while rotating the armature plate in the opposite
direction of engine rotation will advance the timing. Never attempt to
advance or retard the timing by changing the breaker pointgap.
Tighten armature plate retaining screws (7),and re-check timing repea-
ting the procedure describedin steps
7, 8, and 9.
NOTE :
If timing settings cannotbe obtained, breaker points must be replaced.
If breaker points are corroded or otherwise contaminated, engine may
tend to backfire. Clean!
If breaker points arebadly pitted, they must be replaced.
Replacement armature plates (12 Volts,
40 Watts) may be equipped with a
lighting coil. If coil is not used, it may either be removed prior to
installing the plate
or the 2 yellow leads may be cut off right at the
coil.
11

8
9
1 2
armatureplate
(11)
generator
ignition
generating
netted to kill
switch)
I
yellow/black. leads when
the
coil is
utilized.
I! !

Assembly group 4
SPEEDCONTROL
RM 252 FLYBALL GOVERNOR
Special JLO Tools
Vibration tachometer 000.15.300.100
DISASSEMBLY
4.1. 1 Remove nut
(21), washer (18),and cover (17).
2 Disconnect throttle cable noting the hole position for re-assem-
bly. Remove clip
(9) from linkage and unhook linkage (1).
3 Whenremoving lever (2) note into whichof the 5 holesthe
governor spring (3) is hooked. To remove lever (2)
, remove lock
nut (16), spring washer (15), steel washers (14), and plastic
washer (12). Note sequence. Remove screw
(6) and spring washer
(7) . Slide governor lever (8) out of governor housing.
4 Engine stop contact (10) need not be removed unless it is to be
replaced.
ASSEMBLY
4.2. 1 If engine stop contact(10)has been removed, re-install by
snapping it back into the bore in governor housing. Be sure
recess in flange clears boss
of crankcase.
2 If stud(13) is loose or has been removed, re-install in
crankcase with threadlocking compound.
3Installgovernorlever
(8) withspringwasher (7) and screw
(6).
4 Install lever (2) with washers (14,12), spring washer (15),and
new lock nut (16)
. For precise lock nut tightness please refer
to section "governor adjustment procedure".
5 Install governor spring (3) in appropriate hole of levers 2 and
8.
6 Install governor linkage (1) and secure with new clip (9).
7 Connectthrottle cable.
8 Cover (17) with washer (18) and nut (21) should be installed
after governor has been properly adjusted. Please refer to
corresponding section in this manual.
NOTE
:
Bolts(22) too long or insertedincorrectlymight jam the
governor shaft (23). (Observe reach of screw!)
When bolts (22) are inserted correctly, lever must move freely
(ill. II).
13

b

Assembly group 4
ADJUSTMENT INSTRUCTIONS-MECHANICAL
Special JLO Tools
Vibration tachometer 000.15.300.100
STOP-, IDLE-, AND NO-LOAD ADJUSTMENT with the blade fitted
NOTE
:
Check main and idle jet of carburettor for cleanliness. Set air adjusting screw
(7) (it should be set 1/2 a turn out).
Preparations:
1. Move both speed lever (1) and throttle lever on mower handle into "Run"
(Max.) position.
2. Hook piano wire
(3) into lever (1) using the original hole position (2).
Lightly retain the outer cableby means of screw (19) and clamp (4).
Adjustment of No-Load Speed (throttle wide open):
3. Hook spring (11) into lever (1) for initial adjustment. (Required no-load
rpm refer to table).
4. Hold lever (1) in RUN (Max.) position and tighten Nylock nut (5) so that the
spring (11) can just move the lever (1).
5. Start engine (take all safety rules into consideration). Check speed with
tachometer, and if necessary adjust by bending spring retainer on governor
lever
(6) into + or - direction. (Refer to illustration and table).
NOTE
:
Bending into + direction = engine runs faster
Bending into
- direction = engine runs glower
(max.
- 3.00 mm corresponds to approx. - 100 rpm)
There is no gap between dampingspring and housing at no load rpm
6. If engine tends to hunt at no-load speed, screw out damping spring (9) until
engine stops hunting.
Adjustment
of Idle Speed:
7. Move speed lever (1) into "Idle" (Min.) position.
NOTE
:
In this position lever and short circuit contact must still have agap of 1
mm.
8. Set the idle speed to 1200-1300 rpm by adjusting carburettor idle set screw
(8).
9. Move speed lever (1) into "Stop" position. In this position the lever (1)
must touch the short circuit contact (10). If necessary, loosen clamp screw
(12) atand adjust outer cable (3).
NOTE
:
Change carburettor jets for operation in higher areas. Following a rule of thumb
every
3000 ft. of altitude above sea level, the main jet should be reduced by one
size. These modifications do not affect the other jetsand adjustments.

e
No-loadadjustment
byspringpositioning
at speedlever wire 1.5 B(C)
bore A approx.2750 rpm wire cover,outer 6 mm
B 2900 "
C 3050
D 3200 "
E 3400 "
I
(
preciseadjustment bybendingtongue at lever
max 3.0 mm correspondwithapprox.100 rpm
/
+ higherno-load rpm
- lower " "
carburettorsurvey ref. to spareparts list
16

Assembly group 4
SPEEDCONTROL
L 252 TOPSPEED LIMITER
Special JLO Tools
Tachometer
- Vibration Type 000.15.300.100
DISASSEMBLY
4.3.
1 Remove carburettor from intake manifold and disconnect air vane rod (1)
from butterfly lever (2) (see illustr. III and IV).
NOTE
:
The butterfly lever (2) is positioned by 2 flats on the butterfly
spindle. When removing the lever, note its original position
(see ill. IV)
.
2 Carefully unhook spring (3) from lever (4) and airvane (5).
3 Loosen hex. nut (7) and remove screw (6) . Disconnect air vane rod (1) .
4 Remove hex. nut (9) , star washer (10), and adjusting lever (4).
ASSEMBLY
NOTE
:
Carefully inspect all air vane governor parts for excessive wear or damage.
Replace if necessary. It is particularly important that the governor spring is
not over- stretched or damaged at thespring ends.
4.4. 1 Connect air vane rod
(1) to air vane (5). Fit hex. screw (6) through
air vane
(5) , fit hex. nut (7) and lock washer (8) , and install in boss
provided on cylinder (see illustr. I). Do not apply any lubricant to
air vane/spindle!
2 Tighten hex. nut (7) so that air vane moves freely radially on hex.
screw (spindle)
(6) with only a little axial play.
3 Connectother end of airvanerod
(1) to lever (2) of carburettor
butterfly spindle. Install carburettor on intake manifold.
NOTE
:
With the air vanein position "C", the butterfly valve in the carburet-
tor must be in the fully open position (throttle wide open).
4 Install adjusting lever
(4) with star washer (10) and hex. nut (9).
5 Carefully hook spring (3) into both holes of air vane (5) and lever (4)
as shown in illustr. II.
SPEED ADJUSTMENT
6 Start the engine, observing safety regulations.
7 Loosen hex, nut (9) , insert small punch or drill into holeprovided in
lever, and rotate lever to obtain desired engine speed.
NOTE
:
A = Higher spring tension = higher speed
B
= lower spring tension = lower speed
8 When desired speed has been obtained, tighten hex. nut (9) securely and
re-check engine speed with tachometer.

I
18