Yamaha MA190 User manual

SERVICE MANUAL
MA190
7JD-F8197-E0
2017.10×1 !

FOREWORD
This manual was written by the Yamaha Motor
Powered Products Co., Ltd. primarily for use
by Yamaha dealers and their qualified mechan-
ics. It is not possible to put an entire mechan-
ic’s education into one manual, so it is
assumed that persons using this book to per-
form maintenance and repairs on Yamaha
Multi-Purpose Engine have a basic under-
standing of the mechanical precepts and pro-
cedures inherent to Multi-Purpose Engine
repair technology. Without such knowledge,
attempted repairs or service to this model may
render it unfit for use and/or unsafe.
Yamaha Motor Powered Products Co., Ltd. is
continually striving to further improve all mod-
els manufactured by Yamaha. Modifications
and significant changes in specifications or
procedures will be forwarded to all Authorized
Yamaha dealers and will, where applicable,
appear in future editions of this manual.
HOW TO USE THIS MANUAL
PARTICULARLY IMPORTANT
INFORMATION
Particularly important information is distin-
guished in this manual by the following nota-
tions.
This is the safety alert symbol. It is used to
alert you to potential personal injury haz-
ards. Obey all safety messages that follow
this symbol to avoid possible injury or
death.
DANGER
A DANGER indicates a hazardous situation
which, if not avoided, will result in death or
serious injury.
WARNING
A WARNING indicates a hazardous situa-
tion which, if not avoided, could result in
death or serious injury.
NOTICE
A NOTICE indicates special precautions
that must be taken to avoid damage to the
machine or other property.
TIP
A TIP provides key information to make proce-
dures easier or clearer.
MA190
SERVICE MANUAL
©2017 by Yamaha Motor Powered
Products Co., Ltd.
1st Edition, October 2017
All rights reserved. Any reprinting or
unauthorized use without the written
permission of Yamaha Motor
Powered Products Co., Ltd.
is expressly prohibited.

ILLUSTRATED SYMBOLS
(Refer to the illustration)
SYMBOL DEFINITION SYMBOL DEFINITION
T
R
.
.
Tightening torque Wear limit, clearance
Engine speed Electrical data
Special tool

I. PARTS DESCRIPTION
1-1 Part description.....................................1
1-1-1 Feature ...........................................1
1-1-2 Model & serial number ...................1
1-2 Specification..........................................2
1-3 Service limit...........................................3
II. DIMENSION AND TORQUE
2-1 Engine dimension .................................4
2-1-1 Appearance dimension...................4
2-1-2 Installation hole position.................5
2-1-3 P.T.O. dimension figure ...................5
2-2 Torque value...........................................8
2-3 Standard torque value ..........................9
2-4 Important bolt torque value .................9
III. MAINTENANCE
3-1 Maintenance schedule .......................10
3-2 Change oil............................................11
3-3 AIR CLEANER......................................13
3-4 Fuel parts.............................................14
3-4-1 Strainer clean ...............................14
3-4-2 Fuel check ....................................14
3-5 Spark Plug Service .............................16
3-6 Valve clearance adjustment ...............17
3-7 Governor adjusting.............................19
IV. DISASSEMBLING AND
SERVICING
4-1 Troubleshooting...................................20
4-1-1 Starting difficult.............................20
4-1-2 Power lack ....................................22
4-1-3 Unstable speed ............................23
4-1-4 Unable to ignite ............................23
4-1-5 Engine overheat ...........................24
4-1-6 Abnormal sound ...........................24
4-1-7 Exhaust gas color abnormal.........25
4-2 Preparation of servicing.....................25
4-2-1 Safety precautions........................25
4-2-2 Special tools................................26
4-3 Engine ..................................................27
4-3-1 Recoil starter/housing ..................27
4-3-2 Fuel tank.......................................28
4-3-3 Ignition coil/flywheel .....................29
4-3-4 Muffler ..........................................32
4-3-5 Air cleaner ....................................33
4-3-6 Carburetor ....................................34
4-3-7 Throttle control..............................37
4-3-8 Timing chain .................................38
4-3-9 Cylinder head/valve train..............43
4-3-10 Crankcase cover/
governor gear.........................................49
4-3-11 Crankshaft/piston/crankcase ......50
4-4 Electric diagram ..................................58

1
I. PARTS DESCRIPTION
1-1 Part description
1-1-1 Feature
Muffler
Spark plug
Starting lever
Oil dipstick
Drain plug
Fuel tank
Fuel tank cap
Engine switch
Air cleaner
1-1-2 Model & serial number
YAMAHA MA190
7-
Engine model
Serial number
1-1 Part description

2
1-2 Specification
Model
Specification MA190
L × W × H (not including crankshaft
output terminal) 425 × 360 × 290 mm
Dry Weight 11.5 or 14.5 kg
Engine Type Single cylinder horizontal, 4-stroke, (OHC)
Displacement 189 ml
Bore × Stroke 68 mm × 52 mm
Theoretical Maximum Power 3.72 kW/3600 r/min
Recommended Using Power 3.5 kW/3400 r/min
Maximum Torque 11.2 N·m/2500 r/min
Fuel Consumption 395 g/Kw·h
Cooling System Forced air
Ignition System Capacitance discharge type
PTO Shaft Rotation Vertical shaft output
1-2 Specification

3
1-3 Service limit
Unit: mm
Parts Item Standard Service limit
Engine Maximum speed (No load)
Cylinder compression
3800±100 rpm
1.15 Mpa at 1200 rpm
—
—
Cylinder head Sleeve I.D. 68.00–68.02 68.160
Cylinder head War page 0–0.05 0.100
Piston
Skirt O.D.
Piston-to cylinder clearance
Piston pin bore I.D.
Piston pin O.D.
Piston pin-to-piston pin bore clearance
67.989–67.971
0.011–0.049
16.004–16.01
15.994–16.00
0.004–0.016
67.850
0.120
16.450
15.940
0.060
Piston rings
Ring side clearance: first/second
Ring width: first/second
Ring end gap: first/second
0.04–0.08/0.04–0.08
2.60±0.10/2.70±0.10
0.13–0.28/0.20–0.40
0.150
2.300
1.000
Connecting
rod
Small end I.D.
Big end I.D.
Big oil clearance
Big end side clearance
16.005–16.021
30.000–30.018
0.019–0.049
0.4–0.7
16.090
30.066
0.120
1.100
Crankshaft Crankshaft pin O.D. 29.969–29.981 29.910
Valve
Valve clearance IN
EX
Stem O.D. IN
EX
Guide I.D. IN
EX
Stem clearance IN
EX
Seat width
Spring free length
0.10–0.15
0.15–0.20
5.440–5.455
5.430–5.445
5.500–5.520
5.500–5.520
0.045–0.080
0.055–0.090
0.85
30.50
—
—
5.310
5.300
5.590
5.590
0.100
0.120
2.000
28.500
Camshaft
Cam height IN
EX
Journal I.D.
23.98
27.88
9.00–9.04
23.730
27.630
9.090
Camshaft
spindle camshaft spindle O.D. 8.96–8.98 8.910
Spark plug Gap 0.7–0.8 —
Ignition coil
Resistance Primary coil
Secondary coil
Air gap (at flywheel)
0.8–1.0 Ω
5.9–7.2 kΩ
0.40–0.60 mm
—
—
—
1-3 Service limit

4
II. DIMENSION AND TORQUE
2-1 Engine dimension
2-1-1 Appearance dimension
360
290 425
2-1 Engine dimension

5
2-1-2 Installation hole position
2-1-3 P.T.O. dimension figure
Type : 7/8"-1-1.1 Type : 7/8"-1-1.2
4.76
19.5 -0.15
0
22.2 -0.025
0
+0.05
0
7.07 2.5
19 +2.5
0
46.3 1.2
+
-
28 1
+
-
MOUNTING SURFACE
27
M10 1.25
16
4.76
19.5 -0.15
0
22.2 -0.025
0
+0.05
0
7.07 2.5
19 +2.5
0
44.45 1.2
+
-
MOUNTING SURFACE
27
M10 1.25
16
25 +1
0
2-1 Engine dimension

6
2-1 Engine dimension
Type : 7/8"-3 Type : 7/8"-4
4.76
19.6 -0.15
0
17.7 -0.15
0
+0.05
0
4+0.03
0
22.2 -0.025
0
7.07 2.5
25.4 +2.5
0
61.9 1.2
+
-
MOUNTING SURFACE
27
25.4
32 +1
0
10.3 0.2
+
-
3/8-24UNF
16
4.76
19.6 -0.15
0
2 17.7 -0.15
0
+0.05
0
22.2 -0.025
0
7.27 2.5
25.4 +2.5
0
80.2 1.2
+
-
MOUNTING SURFACE
27
25.4
40 +1
0
10.3 0.2
+
-
46.7 0.2
+
-
3/8-24UNF
16
2
2 4 +0.03
0
Type : 1"-1 Type : 1"-2
6.35
21.8 -0.15
0
25.4 -0.025
0
+0.05
0
7.03 2.5
25.4 +2.5
0
46.03 1.2
+
-
MOUNTING SURFACE
27
3/8-24UNF
26 +1
0
25.4
6.35
21.8 -0.15
0
+0.05
0
25.4 -0.025
0
7.07 2.5
25.4 +2.5
0
61.9 1.2
+
-
MOUNTING SURFACE
27
3/8-24UNF
32 +1
0
25.4
Type : 1"-3 Type : 25-2
6.35 +0.05
0
21.8 -0.15
0
19.9 -0.15
0
5+0.03
0
25.4 -0.025
0
7.07 2.5
25.4 +2.5
0
61.9 1.2
+
-
MOUNTING SURFACE
27
32 +1
0
37 0.1
+
-
3/8-24UNF
19
25.4
6.35 +0.05
0
21.3 -0.1
0
20.7 -0.15
0
2 4.76 +0.03
0
7.07 2.5
80.2 1.2
+
-
MOUNTING SURFACE
27
40 +1
03/8-24UNF
16
2
30
46.7 0.2
+
-10.3 0.2
+
-
25 -0.025
0
25.4

7
2-1 Engine dimension
Type : 25-3
4.76
9.75 -0.15
0
+0.05
0
5 2.5
80.2 1.2
+
-
MOUNTING SURFACE
27
50 +1
0
31 min
25 -0.05
-0.03
7/16-20UNF
19

8
2-2 Torque value
2-2 Torque value
Ser. No Item Specification Performance class Torque value (N·m)
1Cylinder head M8 × 65 10.9 26±2
2Crankcase cover M6 × 30 8.8 10±2
3Oil drain plug M10 × 15 8.8 22±2
4Connecting rod M6 × 35 10.9 13±1
5Valve locking nut M5 8 6±2
6Governor gear M6 × 16 8.8 10±2
7 Flywheel
M14 (iron flywheel) 8 78±4
M14 (aluminum
flywheel) 8 64±4
8Spark plug M14 × 1.25 8.8 22±2
9Cylinder head cover M6 × 12 8.8 8±2
M6 × 80 8.8
10 Breath groove covering plate M6 × 12 8.8 10±2
11 Brake M6 × 12 8.8 10±2
M6 × 20 8.8
12 Ignition coil M6 × 20 8.8 10±2
M6 × 68 8.8
13 Stud supporting bolt M6 × 80 8.8 10±2
14 Lower shell M6 × 16 8.8 10±2
15 Muffler stud M8 × 109 8.8 12±2
16 Muffler nut M8 8 22±2
17 Air cleaner M6 8 8±2
18 Throttle control M6 × 12 8.8 10±2
19 Governor support lock nut M6 8 8±2
20 Recoil starter M6 8 8±2
21 Fuel tank M6 × 25 8.8 5±1
M6 8 8±2
22 Engine housing M5 × 20 8.8 6±2
TIP
For unspecified bolt, screw and nut, refer to the standard torque value.

9
2-3 Standard torque value
Fasteners Thread dia. (mm) Torque value (N·m)
Bolt and nut
5 mm bolt, nut 4.5–6
6 mm bolt, nut 8–12
8 mm bolt, nut 18–25
10 mm bolt, nut 29–34
12 mm bolt, nut 49–59
4 mm screw 1.5–2.6
5 mm screw 3.5–5
6 mm screw 7–11
5 mm flange bolt 3.6–6.9
6 mm screw 7–11
5 mm flange bolt 3.6–6.9
6 mm flange bolt 10–14
8 mm flange bolt 20–26
10 mm flange bolt 35–45
2-4 Important bolt torque value
Item Thread dia. (mm) Torque value
N·m Kg·m
Connecting rod bolt M6 × 1.0 13 1.3
Cylinder head bolt M8 × 1.5 26 2.6
Flywheel nut M14 × 1.5 52 5.2
Crankcase cover bolt M6 × 1.0 10 1.0
Value locking nut M5 × 0.5 6 0.6
2-3 Standard torque value/2-4 Important bolt torque value

10
III. MAINTENANCE
3-1 Maintenance schedule
Good maintenance is essential for safe, economical, and trouble-free operation. It will also help
reduce air pollution.
WARNING
Exhaust gas contains poisonous carbon monoxide. Shut off the engine before performing
any maintenance. If the engine must be run, make sure the area is well ventilated.
Periodic maintenance and adjustment is necessary to keep the generator in good operating condi-
tion. Perform the service and inspection at the intervals shown in the Maintenance schedule below:
Maintenance schedule
Frequency
Item
Each time
First
month or
20 hrs
Each
season or
50 hrs
Every 6
month or
100 hrs
Each year
or 300 hrs
Engine oil
Oil level
check √
Replace √ √
Air cleaner
Check √
Clean,
replace √
Spark plug Check, clean √
Adjust √Replace
Fuel strainer Clean √
Valve
clearance Check, adjust √*
Cylinder
head Clean √*
Fuel tank Replace Every 3 years
Cylinder
head/piston
Clean carbon
deposit Each 150 hours*
“*” This items should be serviced by company authorized dealer, unless you have the proper tools
and mechanically proficient.
TIP
Service more frequently when used in dusty areas.
3-1 Maintenance schedule

11
3-2 Change oil
Change oil
TIP
Drain the engine oil rapidly and completely out
when the engine is hot.
1. Remove the oil dipstick, drain plug and
washer and tilt the engine to drain engine
oil thoroughly.
2. Reinstall the drain plug and washer screw
in it securely by hand.
3. Remove the dipstick and clean oil.
4. Refill the recommended clean oil and
check oil level. Stop the engine and place
it on the level ground when checking.
MA190 engine capacity:
0.6 L
Check as following:
a. Insert the dipstick into the filling hole
without screwing down and check the
oil level.
b. If the oil level is too low, add the rec-
ommended engine oil up to the oil
upper limit.
5. Reinstall the dipstick and screw down.
6. Tighten the oil drain plug.
MA190 Oil drain plug:
20–24 N·m
TIP
Use 4-stroke engine oil, API service classifica-
tion SE class or equivalent. Always check the
API service label on the oil container to be
sure it includes the letters SE or equivalent.
SAE10W-30 is recommended for general use.
Other viscosities shown in the chart may be
used when the average temperature in your
area is within the indicated range.
Recommend user to use SF class or equiva-
lent.
3-2 Change oil
Washer
Oil dipstick
Drain plug
Upper limit
Lower limit
Figure

10 01020 30
40 60 80 100
20
20 20
0
40ć
eF
30
10W30
5W 30
SAE VISCOSITY CLASS
ENVIRONMENT TEMPERATURE

12
WARNING
Engine oil is a major factor affecting
engine performance and service life. Non-
detergent and 2-stroke engine oils will
damage the engine.
TIP
For environment protecting, please properly
handle with the used oil. Running with insuffi-
cient engine oil may damage the engine
severely and it will not be covered the range
of the warranty.
NOTICE
Used engine oil may cause skin cancer if
repeatedly left in contact with the skin for
prolonged periods. Although this is unlike-
ly unless you handle used oil on a daily
basis, it is still advisable to thoroughly
wash your hands with soap and water as
soon as possible after handling used oil.
3-2 Change oil

13
3-3 AIR CLEANER
TIP
A dirty air cleaner will restrict air flow to the carburetor. To prevent carburetor malfunction, clean
the air cleaner each 50 hours (or three month) and service the air cleaner regularly. Service more
frequently when operating the generator in extremely dusty areas.
WARNING
Using gasoline or flammable solvent to clean the filter element can cause a fire or explosion. Use
only soapy water or nonflammable solvent.
Never run the engine without the air cleaner. Rapid engine wear will result.
Nut M6
Air cleaner seat Air cleaner
element
Air cleaner shell
Connecting bolt
1. Screw off the connecting bolt and remove the air cleaner shell.
2. Remove foam element or paper element. Be careful to prevent dirt and debris from falling into
the air cleaner base opening.
3. Clean the element.
Polyurethane element: Clean polyurethane with detergent, then, blow it dry with compressed
air or squeeze it dry. Dip the element in clean oil, then, forcefully squeeze it dry and install it
back. Tap the element lightly several times on hard surface to remove excess dirt or blow
compressed air lightly from the inside out. If dirty, replace in time.
NOTICE
Polyurethane element containing too much oil will jam the strainer holes.
4. Check, clean or replace damaged air cleaner parts.
5. Reassemble the air cleaner element into the shell, cover the shell on and assemble the air
cleaner all parts.
3-3 AIR CLEANER

14
3-4 Fuel parts
WARNING
Don’t smoke or use flame fires near the
flammable solvents.
3-4-1 Strainer clean
1. Put the fuel into the container.
2. Lose the clip, remove oil tube and pull the
strainer out.
3. Check the strainer for damaged and
clean the strainer in the container.
4. After cleaning, reassemble the strainer on
the fuel tank connect oil tube and tighten
the clip.
TIP
Check all connecting position for leaking.
3-4-2 Fuel check
1. Remove the fuel tank cap and check fuel
level.
2. If the level is too low, refuel the tank.
Remember adding fuel, but, not over the
fuel upper level.
WARNING
1. Gasoline is extremely flammable and is
explosive under certain conditions.
2. Refueling in a well-ventilation area with
the engine stopped. Do not smoke and
allow flames or sparks in the area where
gasoline is stored or where the fuel tank
is refueled.
3. Do not overfill the fuel tank (The fuel will
not exceed 3/4 of the fuel tank). After
refueling, make sure the fuel tank cap is
set back securely.
4. Be careful not to spill fuel when refu-
eling. Spilled fuel or fuel vapor may
ignite. If any fuel is spilled, make sure
the area is dry before starting the
engine.
5. Avoid repeated or prolonged contact
with skin or breathing of fuel vapor.
6. Keep out of reach of children.
3-4 Fuel parts
Furl tank Bolt M6 × 25
Tank cap
Tube
Clip
Clip
Clip
Strainer
Fuel tank
Upper limit (3/4 position of the fuel tank)
Fuel

15
MA190 fuel tank capacity:
1.0 L
Only use unleaded gasoline and recommend
gasoline grade 90# over.
Unleaded gasoline can reduce gasoline
engine carbon deposit and prolong the
exhaust system service life.
Never use contaminated gasoline or mixed
gasoline with oil. Don’t allow the dust, foreign
matter or water entering into fuel tank.
NOTICE
9Fuel may damage the oil paint and plas-
tic. Be careful not to spill fuel when refu-
eling. Any damage due to fuel spilling is
not within valid warranty.
“Light knocking” or “spark exploding”
sound can be hear when the engine
overloading. It is normal. Do not be
worry about that.
If “knocking” or “spark exploding” sound
occur at a steady speed under normal
load, change grade of gasoline; if such
phenomena still happen, consult your
dealer for help, otherwise the engine
may be damaged.
9When the engine is running, continuous-
ly “knocking” or “spark exploding”
sound occurring will damage engine.
“knocking” or “spark exploding” sound
from misusing will not be within the
valid warranty.
3-4 Fuel parts