Yamaha GP 338F Building instructions

VA AHA ' .. ..
, .
, .. 8101108111
GP 338F / GPK433F
. SIRVICIMAIUAI
~

TABLE OF CONTENTS
CHAPTER 1. GENERAL ....... .... ... . ......... ...... . ....... ...... ..
1 -1 . Specifications ..............
.. .. . .. .............. .... ............. .. .. .. . .. .. .... .. . ... ........... ... .................. .. . ..
1-2. Service Data
1-3. Tools .........
CHAPTER 2. ENGINE
2-1 .
2-2. Removing the
Engine.
Starter .....
2-2-1. Removal
2-3. Primary Sheave .......... ..........
2-3-1. Disassembly.
2-3-2. Cleaning and Inspection .. ................. .. .. .
2-3-3 . Assembly
5
5
6
7
7
.. ...... .. ..... 8
9
9
2-4 . C.D.I. Magneto .................. 11
2-4-1. Removal .............. ........ ........... .. ............ .. ........... .. . .. . .. .. .. . .. ..... .. ......... .. ... .. .. .. ........... 12
2-5. Carburetor ........... ............... 14
2-5-1. Removal.
2-5-2. Disassembly (GPX338F)
2-5-3. Cleaning and Inspection (GPX338F) ........................ .. ............ .. .. . .. . .. ........ .. . .. . .. ..... ..
15
16
17
18
18
18
2-5-4. Assembly (GPX338F) ... ...............
2-5-5. Installation (GPX338F)
2-5-6. Adjustments (GPX338F) .
2-5-7. Disassembly (GPX433F) .... 20
2-5-8. Cleaning and Inspection (GPX433F) ..... .. .......... .......... .. .. .. ... 20
2-5-9. Assembly (GPX433F) .... ........ . ....... .... ... .. .... .. . .. . .. .. .. . .. ....... .. .... .. ............... .. . .. .... 21
2- 5-10. Installation (GPX433F)
2-5-11. Adjustments (GPX433F).
2-5-12. Carburetor with Accelerator Pump (GPX433F)
..... 21
.
.. 21
... 23
2-6. Oil Pump ........................ .. ...... .. . .. ........ .. .. ...... .. . .. ... 24
2-7 . Engine .....
2-7-1. Disassembly ........... .. .. .
CHAPTER 3. POWER TRAIN
3-1. Secondary Sheave .................
.. . .. .
3-1-1. Removal
3-1-2.
3-1-3.
3-1-4.
Cleaning and Inspection.
Assembly ..
Adjustments ...... .......
3-2. Disc Brake ................
3-2-1.
3-2-2.
3-2-3.
3-2-4.
Removal ....
Cleaning and Inspection
Installation
Adjustments
3-3. Chain Housing ............ .. ....... ..
3-3-1 .
3-3-2.
3-3-3.
Removal
Cleaning and Inspection
Assembly
..
.. .. .. .. .. . ...... . 26
.. .. ..... .. .. ................................................... 26
... 29
...29
30
30
.. .. .... .. ...... .... .... ... 30
.. .. .. . .. . .. ..... ....... 33
. ........... ............... 35
..." ............. .. .... 36
...36
.... 36
.... 37
. .. .. .... ............. ... ........... .. ............ ... 38
.... 39
. ... 39
. .. 40

Front Axle
Rear Ax l e.
........ .. . .. .. ......... .. . .. .. .. ... .. .. ...... .. ...... .. .. . 41
......
.. . .. .. .. . ... . .. .. .. . .. .. .. ..... .......... .. . ....... 42
3-4.
3-5 .
3-6. Sliding Suspension .........
.. ... .. .. ...... .. .............. .... .... .. .. ........ .. ...... .. ..... .. ...... .. ... .. .. . .. ........ .. . 43
CHAPTER 4. STEERING (SKI) AND CHASSIS . .. . ... .. ... . ...... . .. ....... .. . ... .. . .. . .. . .. . ... .. ..... 45
4-1 . Frame ............. .. .. .. .. .. ..... ...... .. ...... .. . ..... . .. ... .. . ... . ... .. .. .. ... .. .... ... .. .... .. .. ....... .. .. .. .... .. ..... .. ... 46
4-2. Engine Mount .....
.. ...... . .. .. ... .... .. .
4-3. Oil and Fuel...... .. .. . .. ......... .. .............
4-4. Ski .
.. ........... ....... .. .. .. .. ...
Steering ..............
Control Wires
.... 48
.
.. ..... .. .... .. . .. .................. .. .. .. .... .. .. .. ...... .. 48
....... .. ...... .. ............. .. .... .. .. .. ............ .. 48
.....
48
... 48
4-5.
4-6.
4-7. Shroud
.. ..... ... ............. .. ........... .. .... .. .... .. .. ...... .. ......... .. .. ....... .. . .. ... .. ........ .. .. .. .. .. . .. ...... .. ......... 48
CHAPTER 5. ELECTRICAL SYSTEM
.. .. ........ .. ... ..... .. ...... . .. . .. .. .. ..... 49
CHAPTER 6.
TIGHTENING TORQUE . ... .... .. . .. ................. .. .. .. .. .. .. .. .... .. .. ... .... .. .. ... .. .. 57

GENERAL -Specifications, Service Data
CHAPTER 1. GENERAL
1 -1 . Specifications
Model
GPX338F GPX433F
Dimensions & Weight:
Overall length (including the ski)
98.8 ins. (2,510 mm.) 98.8 ins. (2,510 mm.)
Overall width
39 .8 ins. (1,010 mm.)
39.8 ins. (1 , 010 mm.)
Overall height (including the windshield) 38.0 ins. (965 mm.)
38.0 ins. (965 mm.)
Engine:
Type
Two-stroke five-port induction
Two-stroke five-port induction
aluminum cylinder
aluminum cylinder
No. of cylinders & arrangement Parallel
twin Parallel twin
Displacement
20.62 cu.in. (338 c.c.)
26.42 cu.in. (433 c.c.)
Bore & stroke
2.362 x 2.346 ins. (60 x 59.6 mm.)
2.677 x 2.346 ins. (68 x 59 .6 mm.)
Cooling system Natural air cooled Natural air cooled
Lubrication system
"Autolube" oil injection
"Autolube " oil injection
Oil tank capacity
2.4 qts. (2.25 lits.) 2.4 qts. (2.25 lits.)
Starting System: Recoiled hand starter Recoiled hand starter
Fuel System:
Fuel Gasoline (high-octane) Gasoline (high-octane)
Fuel
tank capacity
6.0 US.gal. (23.0 lits.) 6.0 US.gal. (23.0 lits.)
Carburetor Diaphragm type Diaphragm type
MIKUNI BN38-34SH x 2 KEIHIN
CDX42-38 x 2
Ignition and Electrical Systems:
Ignition system Flywheel
magneto (CD I)
Flywheel magneto (CDI)
Headlight 12V.
60 / 60W. (High/ Low beams) 12V.
60/60W. (High/Low beams)
Taillight
12V . 8W.
12V.8W.
Stoplight
12V.23W.
12V.23W.
Meter lamp
12V . 3W.
12V . 3W.
Frame: Fabricated
aluminum and steel Fabricated
aluminum and steel
Drive track:
Molded rubber, steel reinforced
Molded rubber, steel reinforced
with cleats
with cleats
Transmission:
V-belt automatic transmission
V-belt automatic transmission
Brake: Disc brake Disc brake
1 -2. Service Data
Model
GPX338F GPX433F
Engine:
Cylinder head tightening torque Nuts:
16 .6 - 19 .5 ft-Ibs.
Nuts : 16.6 - 19.5 ft-Ibs .
(2.3 - 2.7 m-kgs.) (2.3 -
2.7 m-kgs.)
Bolts :
14.5 - 16.6 ft -Ibs. Bolts: 14 .5 - 16 .6 ft-Ibs.
(2.0 - 2.3 m-kgs.)
(2.0 - 2.3 m-kgs.)
Piston clearance
0.0018 - 0.0020 in.
0.0018 - 0.0020 in.
(0045 - 0.050 mm.) (0.045 - 0.050 mm.)
Lubrication oil
Yamalube or Johnson outboard oil
Yamalube or Johnson outboard oil
Ignition timing
B.T.D.C. 1.6±0.1 mm.
BTD.C . 1. 6±0.1 mm.
-1-

GENERAL -Service Data, Tools
Model
Compression ratio
Idling speed
Spark plug
Carburetor:
Model
Number of turns out
Main adjuster
Slow adjuster
P.J.
S.J.
Fuel level
Valve seat
Ski width
Drive track deflection
Oil pump
Note:
Minimum stroke
Maximum stroke
GPX338F
7.8 : 1
2,100 r.p.m.
N.G.K. B-9EV
MIKUNI BN38-34SH x 2 (87800)
L. R: 1±' 1/8
L. R: 3/4
#8 5 (Spare #95)
0.059 in. dia. (15 mm¢)
29.5 ins. (750 mm.)
0.69 -0.71 in. (17. 5±5 mm.)
0.20 - 0.25 mm.
1.60 - 1.78 mm.
#95 pilot jet should be used when the engine speed
acceleration is
not smooth at temperatures below
0° C at low altitudes.
1-3 _ Tools
To service the snowmobile , the following tools are re-
quired.
o Special tools
o Gauges (Measuring instruments )
1. Special Tools
2-b.
o General tools
o Standard tools
GPX433F
7.0: 1
2,500 r.p.m.
Champion N-2G
KEIHIN CDX42-38 x 2 (87900)
L. R:
L, R:
#65
#45
1±118
1-3 /8
0.059 in. dia. (1 .5 mm ¢ )
29.5 ins. (750 mm.)
0.69 -0.71 in. (17.5±5 mm.)
0.20 - 0.25 mm .
1.60 - 1.78 mm .
1-a. Crankshaft separator
1-b . Crankshaft jig 1-f.
Wedge
2- c. Magnet puller attachment
5. Sheave
gauge
1-c. Press bo x
1-d. Press
pin
1-g . Stop (56 mm .)
2-a.
Magnet puller body
2-b . Magnet puller screw
2-d .
3.
4.
Fig. 1- 1
- 2 -
Screw , 8-mm. L : 80 mm . 6. Primary fixed sheave puller bolt
Dial gauge stand #2
7-a. Primary sheave
inst a ller / remo ver 2
Sock
et end wrench
7-b.
Primary sheave installer/remover 1

GENERAL -Tools
2. Gauges
4
· ~
~
... .
~- .~
2 3
6
13
1. Feeler gauge 8. Coil
tester
2. Dial gauge 9. Electro
tester
3. Micrometer
10. Scale
4. Cyli nder gauge
11 . Spring balance
5. Vernier calipers
12 . Pocket tester
6. Torque wrench 13
Tachometer
7. Point checker
Fig. '-2
3. General Tools
18
1.
Plug wrench 11 . Phillips-head
screwdriver (large)
2
Set of open-end wrenches
12. Phillips-head
screwdriver (medium)
·3
Set of socket wrenches 13.
Slotted-head screwdriver (medium)
4.
Soft -faced hammer 14 .
Slotted-head screwdriver (large)
5.
Steel hammer 15.
Slotted-head screwdriver (small)
6. Circlip pliers
(S T type) 16. T-hand l e. socket wrench
7. Circlip pliers (RT type) 17. L-handle socket
wrench
8. Needle-nose pliers 18.
Torque wrench and sockets
9. Pliers
19 . Scraper
10.
Ph illips-head scr ewd river (small) 20.
Allen wrench (6 mm.)
Fig. 1-3
- 3 -

GENERAL -Tools
4. Standard Tools
2
1. Plier
2.
30 x 22 mm. special wrench
3. 17x14mm. open-end wrench
4. 17 x 13 mm. open-end wrench
5. 12x10mm. open-end wrench
6. 10 x 8 mm. open-end wrench
7.
13 mm . special wrench
Fig. 1-4
- 4-
8.
S
10
11.
12.
13.
14.
6
8
9
10
Point wrench and feel er gauge
13 x 21 mm. plug wrench
Screwdriver handle
11
13
Combination slotted and Phillips-head screwdriver
Phillips-head screw driver
Allen wrench
Tool bag

ENGINE· Removing the Engine
CHAPTER 2. ENGINE
2-1. Removing the Engine
This chapter deals with the procedure for engine removal
from the frame.
The engine can be
removed without removing the car-
buretor . and starter assembly.
The carbu r etor and starter can be removed from the
frame without removing the engine.
Too ls Required:
Pliers
Slotted head screwdriver (M)
10 mm. socket-end wrench
Chisel
Steel head
hammer
Long nose pliers
17 mm . socket-end wrench
1. Remove the four spring hooks and four tension
springs from the exhaust chamber. using pliers. and
then remove the two exhaust chambers.
Next. remove the starter handle from the starter
handle holder .
2. Remove the throttle wires (R & L) and choke wires
from the carburetor assembly.
3. Remove the two spring assemblies from the silencer.
and remove silencer 1. (Fig. 2-1)
Fig. 2-1
4. Remove the six bolts from the carburetor using the
10-mm . open-end wrench. and remove the silencer-
plate. Next. remove the tachometer cable from the
oil pump . (Fig. 2-2. 2-3)
Fig. 2 2
Fig. 2-3
5. Disconnect the lead wire coming from the CDI mag-
neto. Remove the four nuts securing the engine.
and
demount the engine.
Note:
Before demounting or mounting the engine. the pri-
mary sheave must be removed or installed. For
procedure. refer to 20-3. Primary Sheave. For
carburetor removal. refer to 2-5.
- 5-

ENGINE -Starter
2 - 2. Starter
Tools required:
10 - mm . socket wrench
13 - mm . socket wrench
Slotted -head screwdriver (medium)
19
~ / 20
~~
~
I
13
1.
2.
3.
4.
5.
6.
7
8.
9.
10.
Starter case
Sheave
drum
Starter spring
Drive pa wl
Thrust wa sher
Drive plate
spring
Return spring
Return
spr i ng
Drive plate
Thrust washer
3
2
11
11 Spr ing washer
12
Nut
13 . Rope
(Q = 1820)
14. Handle
15. Con nector
16. Starter pulley
17 Bolt
18 .
Spring was her
19 . Bolt
20. Sp ri ng washer
Fig. 2-4
- 6-

For disassembly. assembly. inspection. cleaning and ad-
justment. refer to the GPX338F/GPX433F Service Man-
ual.
2-2-1. Removal
Remove the four bolts holding the starter and remove it
from the crankcase cover. (Fig.
2-5)
Fig . 2-5
2-3. Primary Sheave
1. Primary fixed sheave complete
6. Cam
2. Bushing
7. Primary sheave cap complete
3. Spring seat 8. Lock
was her
4.
Compression spring
9. Bolt
5 Primary sliding sheave complete
10. V-Belt
Fig. 2-6
- 7 -
ENGINE -Primary Sheave

ENGINE - Primary Sheave
Tools required:
Chisel
Steel hammer
Primary fixed sheave puller bolt (Special tool)
Primary sheave installer/remover 1 (Special tool)
Pri
mary sheave installer/remover 2 (Special tool)
22 mm. socket wrench
17 mm. socket wrench
2- 3-1. Disassembly
(1) Straighten the primary sheave assembly mounting
bolt lock washer , using the chisel and steel hamm -
er . (Fig. 2-7)
Fig. 2-7
(2) Install
primary sheave holder 1 (special tool) on the
edges of primary sliding sheave and primary fixed
sheave so that the primary sliding sheave is not
forced by the spring. (Fig. 2-8)
Fig. 2-8
(3) Using
the 22-mm . socket wrench, remove the prima-
ry sheave assembly securing bolt and remove the
primary sheave cap. (Fig. 2-9)
Fig. 2-9
(4)
With primary sheave installer/remover 1 being in-
stalled,
remove the primary sliding sheave and pri-
mary fixed sheave from the crankshaft. (Fig. 2 -10)
--------
Fig. 2-10
(5) Remove the drive belt. (Fig. 2-11)
Fig. 2-11
- 8 -

2-3-2. Cleaning and Inspection
(1) Cleaning
Thoroughly clean all parts in a detergent oil. and dry
them with compressed air.
(2) Inspection
1) Check the primary shaft splines for wear. If worn
excessively, replace.
2) Check the tapered ends of the crankshaft and prima-
ry fixed sheave for scratches. If scratched unduly,
replace.
3) Check the primary spring for fatigue.
If excessively fatigued, replace.
4) Check the primary sheave cap weights for smooth
movement.
Grease the contact area . of the weights with other
parts .
Also grease the weight pivot points.
1. Primary fixed sheave complete
2. Bushing
3. Spring seat
ENGINE - Primarly Sheave
5) If the sliding sheave spline is excessively worn, re-
place.
6) Check the sheave for bends. If bent, replace.
7) If the V-belt width is worn to 26 mm . or less, or if
cracked.
it should be replaced.
It is advisable to replace the V-belt if the machine is
used
for a race.
2-3-3 . Assembly
(1) Place the V-belt around the secondary sheave.
(2) Install the primary fixed sheave, bushing, spring seat.
compression spring, primary sliding sheave as an
assembly on the crankshaft.
Place the V-belt between the primary fixed sheave
and primary sliding sheave. (Fig. 2-12)
4. Compression spring
5. Primary sliding sheave complete
6. V-belt
Fig.212
- 9 -

ENGINE· Primarly Sheave
Note:
Apply Shell Alvania grease #2 or #3 to the primary
fixed sheave.
Clean the tapered portions of the crankshaft and
primary fixed sheave.
(3)
Push in the primary sliding sheave using primary
sheave installer/remover 2 (special tool) and primary
sheave assembly securing bolt. and install primary
sheave installer/remover 1 on the primary fixed
sheave and pri mary sliding sheave. (Fig. 2·13)
Fig.213
(4) With primary sheave installer / remover 1 being in-
stalled, remove primary sheave 2 and primary sheave
assembly securing bolt. Then tighten the primary
sheave cap with the primary sheave assembly secur-
ing bolt.
Next,
remove primary sheave installer / remover 1,
and bend the lock washer . (Fig. 2-14 )
Fig. 2-14
Tightening torque:
Note:
When installing the primary sheave cap, keep the
weights in the position as illustrated . (Fig. 2-15)
Fig. 2-15
- 10-

2-4 . C.D .I. Magneto
Tools required:
10 mm . T-handle wrench
26 mm. socket wrench
Iron bar (12 mm .. length 25 mm.)
13 mm . T-handle wrench
1. Charging coil
2.
Lighting coil 1
3. Lighting coil 2
4 Spacer
5. Pan head
screw
6. Spring washer
7. Pulser
8.
9.
10.
11.
12.
13.
14.
ENGINE· C.D.I. Magneto
19 mm. open-end wrench
Flywheel magnet puller (Special tool)
Impact screwdriver (Phillips large)
Steel head
hammer
(Fig. 2-16)
Panhead screw 15.
Spr ing washer
Spr ing washer
16 .
Rotor assembly
Pla in washer
17. Pan head scr ew
Lead wire assembly
18
Hole cover
Lead
clamp
19.
Crank shaft nut
Lead clamp
20.
Spring washer
Panhead screw
21. Washer
F ig . 2-16
- 11 -

ENGINE· C.D.I. Magneto
2·4 · 1. Removal
(1) Loosen the four bolts and remove the crankcase
cover. (Fig. 2-17)
Fig. 2·17
(2) With the starter assembly removed you will now be
able to remove the magneto assembly. The first
step in this procedure is to remove the flywheel se-
curing nut with a socket wrench 1.02 ins. (26 mm.).
(In this case. to loosen or tighten the flywheel. a
"bar" should be inserted into the hole in the pulley.
The
flywheel can be locked.) (Fig. 2-18)
Fig. 2-18
(3) Remove the bolts
that hold the starter pulley. Once
these bolts are removed . the pulley can be set
aside. (Fig. 2-19)
Fig. 2-19
(4) The flywheel
magneto can now be removed. This
requires the use
of special puller that you will find in
our special tool kit. Be sure to use the three short
screws
that come with the puller when removing the
flywheel.
(Note:
Immediately after the flywheel is removed.
take the
woodruff key off the shaft and attach it to
the flywheel so that it is not lost.) (Fig. 2-20)
Fig. 2-20
(5) All parts of the magneto assembly. except for the
magneto backing plate. have been removed. The
only
time that the magneto backing plate needs to
be removed is in the case of complete engine tear-
down. The backing plate has to be removed in or-
der to split the cases and this is accomplished by
removing the three
of four hold-down screws. with
an impact screwdriver. (Fig. 2-26)
Fig. 2-21
-12 -

(6) Loosen the three ground wire holding screws on the
reverse side of the coil plate. and loosen the four
pulser holding screws (two each per pulser) and four
1. Charging coil
2.
Lighting coil 1
3. Lighting coil 2
4. Spacer
5. Pan head screw
6. SJ;lring washer
7 Pulser
8. Pan head screw
Fig. 2-22
- 1 3-
ENGINE -C.D.I. Magneto
pulser coil holding screws (two each per pulser coil).
Then remove the pulser coils from the coil plate.
9. Spring washer
10. Plain washer
11. Lead
wire assembly
12. Lead
clamp
13. Lead clamp
14. Pan head
screw
15. Spring washer
16. Pan head
screw

ENGINE · Carburetor
2-5.
Carburetor
Long nose pliers
As long as the engine runs smoothly, the carburetor
should not be disassembled unnecessarily. But it should
be cleaned once during the season or periodically accord-
ing to operating conditions.
Service Tools:
Phillips-head screwdriver (medium)
49
50
13-mm. open-end wrench
10-mm. open-end wrench
6-mm. open-end wrench (socket wrench)
Air compressor
Slotted-head screwdriver (medium)
Pliers
Steel head hammer
1. Gasket
2.
Check seat valve
3.
Set check plate
4. Valve seat
washer
5.
Valve seat ass'y (# 1,5)
6. Plate
7.
Spring washer
8.
Pan heed screw
9.
Diaphragm arm
48
10.
Diaphragm spring
t(
/ 11. Lever pin
/ 12. Oval head
screw
f30
13. Main diaphragm
14.
Body gasket 1
15
Body 1
~ ~29
16
Pump diaphragm
17. Body 2
- - -~:
18.
Body gasket 2
19. Check valve
r"
20. Body 3
21. Gasket
22. Cover
23. Screw
24.
Spring washer
25. Pan head screw
26
starter plunger
27. Cable assembly
28. Plunger spring
29. Plunger cap
30. Cap
31 Washer
13
32 Spring
33.
Washer
34. Main adjusting screw
15
35.
Slow adjusting spring
36.
Slow adj usting screw
37.
a-Ring
16
38
Pilot jet (# 85)
14
39.
Washer
11
40. Lock
nut
17
41. Scr
ew
18 42. Spring
19
43.
Throttle screw
44.
Nut
45. Throttle adjuster
46.
Bracket
47 Screw
21
48.
Shaft complete
22
49.
Washer
i---
23
50. Clip
51. Lever
52
Washer
53. Plate
GPX338F
54. Rod
screw
Fig, 2-23
-14-

1. Gasket
2
Pump diaphragm
3 P
um p body 1
4. Gasket
5. Check
va lve
6. Pu
mp body 2
7. Needle valve
8. Valve pin
9.
Arm spr ing
10 . Fl
oat arm
11 . Arm pin
12 . Oval head
screw
13. Washer
14 Fuel level pipe
15 . Screw
16 . Bli nd cap
17 . Plug scr ew
18 . Was her
19 . Diaphragm
20. Compres si on spring
21 . Spr ing seat
22. Pump body 3
23 . Lock n ut
24 .
Stop screw
25 . U-ring
26.
Pan head screw
27 . Pan head sc
rew
28 . Rod
29 . Cap
30. Pu mp body 4
31 Diaphragm
32 . Comp ression spring
33 . Fuel cover
34 . Pan head screw
35.
Spring washer
36. Collar
37. Arm
38. Lever pin
39. Washer
40. Cotter pin
41. Rod
42. Spring
43 . Collar
44 Cl ip
45 . a -ring
46 . Washer
47 Main adjuster spring
F ig . 2-24
2-5-1. Removal
(1) Remove the throttle wire . choke w ire. pulse pipe,
fuel pipe and oil pump control rod, and remo ve the
f our nuts using the 13 - mm . open-end wrench. Then
remove the carburetor from the cylinder.
Be careful not to lose the spacer between the ca r-
buretor flange and the stud bold. (Fig. 2- 2 5)
F ig . 2-25
- 15 -
ENGINE · Carburetor
48 .
Ma in adjuster screw
49 . Spr ing
50 .
Ad just scr ew
51 . Gear
52. Ma in adjuster sc rew
53.
Stay plate
54 . Li nk shaft
55 . Coliar
56.
Spr ing pin
57 Compress i on spring
58.
Pan head screw
59 .
Spr ing washer
60 . stow j et 1#52)
61 . Partial jet 1#68)
62 . Gasket
63 . Plate
64 . Pan head
screw
65 . Spr ing washer
66. Li nk lever
67 . Coliar
68. Collar
69. Washe r
70.
Pan head screw
71 . Co
ll ar
n . Rod
73 . Link lever
74. Connector
75 Lock washer
76 Nut
77.
Pan head screw
78 Washer
79.
Nut
80. Stop screw sp ri ng
81 Stop screw
82. Stay plate
83.
Pan head screw
84 . Spr ing washer
85 Stay plate
86
Pan head screw
87 Spring washer
88 . Stay plate
89. 80 lt
90. Spr ing washer
91. Cable adjuster
92 . Nut
93.
Pan head screw
I )

ENGINE - Carburetor
(2) Remove the two springs. and remove silencers 1 and
2 as an assembly from the silencer plate. (Fig. 2-
26)
Fig. 2-26
(3) Straighten the lock washers, and remove the six
bolts using the 10 - mm. T-handle wrench . Remove
the silencer plate
from the carburetor . (Fig. 2- 27)
Fig. 2-27
Before disassembling the carburetor, its exterior should
be washed with gasoline or petroleum. When using
compressed air, take care not to blow into any small
holes such as the fuel inlet port and impulse port. Oth-
erwise, the compressed air can break the diaphragm .
2-5-2. Disassembly (GPX338F)
(1) Loosen the screw, and remove the cover and gasket
(rubber). Loosen the four screws, and remove body
3, check valve, body 2 gasket, body 2, body 1 gas-
ket, body 1 and main diaphragm. (Fig. 2- 28)
1.
2.
3.
4
5.
3
2
4-----<.
2--~
5
6
7
9
10
i-~11
Main diaphragm 6 Body gasket 2
10.
Body gasket 1 7. Check valve 11.
Body 1 8. Body 3 12.
Pump
diaphragm
9. Gasket
13.
Body 2
Cover
Screw
Spring washer
Pan head screw
Fig. 2-28
(2) Loosen
the oval head screw, and remove the lever
pin, diaphragm arm, diaphragm spring and needle
valve.
Remove the
two pan head screws, and remove the
plate and valve seat (# 1.5).
Remove the
two oval head screws, and remove the
set check plate, check valve seat and gasket.
-16-
Since the check valve seat is very thin, be careful
not to lose or damage. (Fig. 2-29)

1.
Starter plunger
8.
Washer
2. Cable assembly g.
Main adjusting screw
3. Plunger spring 10.
Slow adjusting spring
4 Plunger cap 11
Slow adjusting screw
5. Cap 12.
O-ring
15. Lock
nut
16.
Screw
17.
Spring
18.
Throttle screw
19
Nut
ENGINE - Carburetor
Tightening torque:
Pilot jet 1.45 ft-Ibs. (0 .2 m-kg.)
Valve seat screw 0.723 ft-Ibs. (0.1 m-kg.)
Diaphragm arm screw 0. 723 ft-Ibs. (0.1 m-kg.)
1. Main adjuster screw
2. Pilot screw
Fig. 2-30
6.
Washer
13
Pilot jet (# 85)
20. Adjuster throttle
(4) Do not remove the throttle shaft and the throttle
butterfly.
7. Spring 14.
Washer
21.
Rod screw
Fig. 2-29
(3) Remove the slow adjusting screw and slow adjusting
screw spring as an assembly, using a slotted-head
screwdriver.
Remove the main adjusting screw and spring washer
using a slotted-head screwdriver or by hand.
Do
not remove the two a -rings from the main ad-
justing screw groove.
Using a
slotted-head screwdriver (small), remove the
pilot jet and a-ring.
On the right-hand carburetor, the slow adjusting
screw, main adjusting screw and pilot jet are in-
stalled on the right side of the carburetor, but on the
left-hand carburetor, the pilot jet is positioned on the
right side of the carburetor.
Using the 12-mm. open-end wrench, loosen the
plunger cap, and remove the cable assembly, plunger
spring and starter plunger .
Straighten the lock washer, and loosen the lock nut
using the 10-mm. open-end wrench. Then loosen
the primary venturi holding screw, and remove the
primary venturi and secondary venturi from inside.
(Fig.
2-30)
2-5-3. Cleaning and Inspection (GPX338F)
(1) Cleaning
Clean the carburetor with carburetor cleaner or suit-
able solvent. Remove all rubber components from
the carburetor parts (such as diaphragms and gas-
kets) to prevent the solvent from attaching the rub-
ber.
(2) Inspection
- 17-
1) Check the throttle link mechanism, throttle butterfly
and other moving parts for damage.
If faulty, replace the carburetor body .
2) Check the
carburetor body and pump body, and-if
cracked
or holed, replace.
3) Check the threaded portion of the stop screw, and if
damaged, replace.
4) Check the main diaphragm for center plate position
and any other defect . Replace, if any defect is
found.
5) Check the chek seat valve
for cracks and holes, re-
place if damaged.
6) Check the lever pin,
diaphragm arm, valve seat, and
needle valve for wear or breakage. If excessively
worn or broken, replace.
7) Check the diaphragm spring for fatigue. If it fa-
tigued excessively replace.
8) Check the pump diaphragm . If bent or holed, re-
place.
9) Check the diaphragm spring for fatigue. If it is fa-
tigued excessively, replace.