Yamaha BR250F User manual

o YAMAHA
SNOWMOBILE
SERVICE MANUAl
LI1-12618-00-41 884-28197-10

FOREWORD
This Service Manual has been written to acquaint the mechanic with the dis-
assembly, reassembly, maintenance, and troubleshooting procedures required
to provide optimum performance and longevity of the machine.
The
information herein should be closely studied to avoid unnecessary repairs
and to provide the owner
with a sound, safe, dependable machine.
NOTE; _
The
Research and Engineering Department of Yamaha is continually striving
to
further perfect all models. Improvements and modifications are therefore
inevitable.
In
light of this fact, all specifications within this manual are subject to change
without notice. Information regarding changes is forwarded to all Authorized
Yamaha Dealersassoon asavailable.
YAMAHA MOTOR CO., LTD.
SERVICE
DEPARTMENT
BR250F
SERVICE
MANUAL
©1981 by Yamaha Motor Corporation, U.S.A.
1st edition, June 1981
All rights reserved. Any reprinting or
unauthorized use
without the written
permission of Yamaha Motor Corporation,
U.S.A. is expressly prohibited.
Printed in U.S.A.
LIT-12618-00-41
Particularly
important information is distinguished in this manual by the
following notations:
NOTE:
WARNING:
A NOTE provides key information to make procedures easier or
clearer.
A
CAUTION indicates special procedures that must be followed
to avoid damage to the machine.
A
WARNING indicates special procedures that must be follow-
ed to avoid injury to a machine operator or person inspecting
or repairing the machine.

TABLE OF CONTENTS
GENERAL
ENGINE
CARBURETION
POWER TRAIN
CHASSIS
ELECTRICAL
APPENDIX

CHAPTER 1. GENERAL
1-1. EXTERNAL VIEW " 1-1
1-2. MACHINE IDENTIFICATION 1-2
1-3. TERMS 1-2
1-4. STORAGE 1-2
1-5. PRE-SEASON PREPARATION 1-2
1-6. MAINTENANCE 1-3
A. Periodic Maintenance 1-3
B. Lubrication Intervals 1-4
C. Sealing the Carburetor. 1-5
1-7. HIGH ALTITUDE TUNING 1-5
1-8. SPECIAL TOOLS 1-6

1-1. EXTERNAL VIEW
GENERAL
1-1

1-2. MACHINE IDENTIFICATION 1-3. TERMS
A. Frame Serial Number
The frame serial number is located on the
right-hand side of frame (just below the front
of seat). The first three digits identify the
model. This is followed by a dash. The
remaining digits identify
the production
number
of the unit.
Grease:
Unless
other specified, use a low-tempera-
ture lithium base grease when instructed to
grease a part or component.
Thread-locking compound:
Use Loctite® Lock N' Seal (blue), unless
other wise specified, when applying a
thread-locking
compound to securing hard-
ware.
Oil:
Use Yamalube 2
to oil components unless
another oil is specified.
If a snowmobile will
not be used for several
months, it should be stored in a
proper place
so
that both the engine and the track are not
damaged.
1. Completely drain the fuel tank, and dis-
connect the fuel line from the carbure-
tor.
2. With the engine running at idle, squirt oil
into
the carburetor until the engine dies.
This will distribute oil evenly
throughout
the engine and protect it against rust.
3. Disassemble
the suspension, clean and
grease all parts, and reassemble
the
suspension.
4. Lightly coat all shafts
and axles with
grease.
5. Oil all fittings and wire
controls with a
Iightly oiled cloth.
6. Loosen
the track.
7. Block
the chassis so that the track is off
the floor.
8. Protect
the snowmobile with acovering.
1-4. STORAGE
1-5. PRE-SEASON PREPARATION
8R4-000101
Starting frame serial number
B. Engine Serial Number
The engine serial number is located on the fan
case. The prefix indicates
the engine type and
displacement.
The prefix is followed by a
dash and
the serial number. Normally both
the frame and engine serial numbers are
identical.
Starting engine serial number R246-000101 Perform
the predelivery service as described
in
the predelivery check list before operating
any snowmobile
that has been stored for
several months.
1-2

1~6. MAINTENANCE
A. Periodic Maintenance
Perform the various inspections and services at the indicated intervals; however use this schedule as
aguide only. Depending
upon the operating conditions, certain components may require more fre-
quent servicing.
Every
Check
point
20 hrs. or 40 hrs. or 80 hrs. or When Seasonally
400 km 800 km 1,600 km necessary
(2
ENGINE:
Tighteness of bolts and nuts
Bends, cracks, and wear 0
Abnormal noise 0
Loose connection and breaks in the fuel and pulse pipes 0
Loose connection and breaks in the oil pipes 0
Loose connection and breaks in the oil delivery pipe
0
Recoil starter
Carburetor
• Operation of starter jet
0
• Mixing adjuster (pilot screw) 0
•Idle speed adjustment 0
Operation and adjustment of oil pump
Ignition timing
0
Cylinder compression 0
Cylinder/exhaust pipe decarbonize 0
Spark plug condition, gap, and cleaning 0
Tighten the cylinder**
0
DRIVE;
Tightness of bolts and nuts
Wear on slide runners 0
Primary drive system 0
V-belt
()
Secondary drive system 0
Sheave distance 0
Sheave offset
=
Brake pad wear 0
Brake operation and adjustment 0
Guide wheel rubber 0
Wear of track drive sprockets
Initial
100 km I
Drive track adjustment (60mi) &0
300km
(200mi) I
Breaks in drive track 0
Bends in front and rear axles 0j
Check lock washers 0!
Drive chain adjustment 0i
Chain case oil level 0
** Retighten every 10 hours from the first use.
1-3

Every
Check
point
20 hrs. or 40 hrs. or 80 hrs. or
When Seasonally
400 km
800 km
1,600 km necessary
(250
mil (500 mil
(1,000 rni]
CHASSIS:
Tightness
of bolts and nuts
0
Bends and cracks 0
Welded riveted, joints
0
Ski adjustment
0
Ski runner wear 0
Breaks in fuel tank
0
Cleaning of fuel tank
0
Fuel filter
0
Loose connection and breaks in fuel pipe 0
Breaks in oil tank
0
Oil filter
0
ELECTRICAL:
Wear, breakage of wire covering 0
Breaks in high-tension cord
0
Voltage regulator output
0
Operation of engine stop switch 0
Operation of tether switch 0
Headlight
0
Taillight
0
Brake light
0
B. Lubrication Intervals
Every
Check point
20 hrs. or 40 hrs, or
80 hrs. or
When Seasonallv Oil/Grease
400 km
800 km
1,600 km necessary Brand name
{250 mil
(500 mil
(1,000 mil
ENGINE:
Starter case 0
Oil pump control box
0Aeroshell grease
#7 A or
Pump drive cover 0Esso Beacon
325 grease
Oil in the oil
tank
0
YAMALUBE 2-cycle oil
DRIVE;
Primary sheave weights 0
and roller pins
Molybedenum disulfide
Secondary shaft and 0
snowmobile grease
sliding sheave
Front axle housing 0
Shaft 1 and shaft 2
Light all-purpose grease
(Slide rail) 0
Replace chain caseoil 0Gear oit API
"GL-3"
SAE #75 or #80
CHASSIS:
Steering
column lower
0
bearing
Light all-purpose grease
Steering
column upper
0
bearing
Motor oil
Steering
links
0
Ski column
0
Ski wear plate 0
Light all-purpose grease
Ski retaining
pin
0
Brake cable end stopper 0
and brake lever Esso Beacon
325 gear
1-4

C. Sealingthe Carburetor
ALWAYS
seal the carburetor before turning
asnowmobile on its side
for service. This will
prevent fuel from spilling and creating a
hazard.
1. Plug the fuel-tank vent pipe.
2. Plug both float-bowl overflow pipes or
connect them together.
3. Drain float bowl.
1-7. HIGH ALTITUDE TUNING
To attain the best performance in high altitude conditions, carefully tune the snowmobile as out-
lined below.
Confirm STD settings
•
Carburetor (Page3-3)
• Ignition timing (Page6-2)
•Spark plug (Page6-5)
+
Adjust main jet size according to the chart
!(Page3-3)
Test main jet size
(performance &plug colour)
Not OK
~
Adjust main jet size
(Page3-6) •
II I
Not OK
Not OK
OK
I
OK
Check to seeif gearing is
too high or low
NotOK
OK
Adjust gearing as required
(Page
4-12)
OK Not OK
Not OK OK Check engagement speed and
shift performance
Not OK OK-----r~
High altitude
tuning OK
Adjust primary clutch asrequired
{Page
4-1)
NotOK
OK
Not 01<..
Adjust secondary clutch asrequired
{Page 4-1) OK
1-5

'·8. SPECIAL TOOLS
7.
13.
&-b.
4-d.
4-b.
3.
1.
2.
No. Description Tool No.
1Dial Gauge 90890..Q3097..Q0
2Dial GaugeStand 90890-01195-00
3Dial Gauge Needle (56 rnml 90890-03098-00
4 3-Way Puller A'ssy TLU·90901-05-20 (U.S.A.)
4-a 3-Way Puller Attachment 90890-01803..Q0
4-b 3-Way Puller
Attachment 90890-01804-00
4-c 3-Way Puller Screw 90890-01906-00
4-d Drive Handle 90890--1906-00
4-e 3-Way PuIler Body 90890..Q1848-00
4-f 3-Way Puller
Attachment
90890..Q1873-00
5
Rotor Holding Tool 90890..Q1
235..Q0
608
Primary SheavePuller (M18) TLS-90018-59-02 (U.S.A_)
90890-01898..Q0
6-b Primary SheavePuller Attachment 90890-01899..Q0
7Primary SheaveSubassembly
Tool
TLS-9091 0-60-00
90890-01858-00
8Bushing Tool 90890..Q1883..Q0
9SheaveGauge TLS-9091 0-47-02 (U.S.A.)
90890-01702..Q0
10 Pocket Tester 90890..Q3112-00
11 Electro Tester 90890..Q3021-00
12 AC Regulator Checker 90890..Q3090-00
13 Primary SheaveHolder TLS·90018-80..Q0 (U.S.A,)
90890..Q1701-00
14 Secondary SheaveHolder 90890..Q1872-00
1-6

CHAPTER 2. ENGINE
2-1. ENGINE REMOVAL 2-1
2-2. DISASSEMBLY AND INSPECTION 2-2
A. Recoil Starter 2-2
B. Flywheel Magneto 2-3
C. Oil Pump 2-4
D. Top End 2-6
E. Bottom End 2-10
2-3. ASSEMBLY
AND ADJUSTMENT 2-12
A. Bottom End 2-12
B. Top End 2-13
C. Flywheel Magneto 2-14
D. Recoil Starter 2-15
E. Oil Pump Gear
Case 2-17
2-4. ENGINE
INSTALLATION 2-19

ENGINE
2-1. ENGINE REMOVAL
You do not have to remove the engine in
order to servicethe following components:
Cylinder,
Piston,
Recoil Starter,
Flywheel Magneto, and
Carburetor
To remove the engine, remove or disconnect
the
following components in the order given
below.
1. Muffler.
2. Drive guard, V-belt, and primary
sheave
(Refer 4-3, A "Removal.")
3. Carburetor (Refer to 3-1, A "Removal.")
4. D-handle from the starter rope. Knot the
rope so
it will not be pulled into the
starter
case.
5. Spark plug wire.
6. Pulsepipe from the fuel pump.
7. Oil line
that feeds the autolube pump.
Disconnect the
joint in the middle of the
line. Do
not let air enter the line.
8. Four flywheel magneto
leads.
9. Hood Iimiter cable.
10. Three engine mounts; remove the engine.
2-1

2-2. DISASSEMBLY AND INSPECTION
A. Recoil Starter
Drive Plate Spring
Drive Pawl
Drive
Plate
/
/
1. Remove the air shroud and the starter
from
the engine.
2. Pull
about four inches of starter rope
from
the cutout in the sheave drum.
Rotate
the sheave drum five times clock- .
wise to release the preload on the starter
spring.
3. Remove
the securing nut, and carefully
disassemble
the starter. Note the relative
position
of each piece. You will have to
reassemble
the starter as shown in the
illustration above.
Be careful when removing
the drive plate and
the sheave drum. There is a preloaded spring
behind each of these items.
2·2

B. Flywheel Magneto
Flywheel Magneto
Fan
1. Using the rotor holding tool, loosen the
securing nut, and remove the flywheel
pulley
from the magneto.
1. Rotor Holding Tool: 90890-01235
2. Remove the six securing bolts and re-
move the fan.
3. Using the 3-way puller, remove the
magneto.
2-3
3-Way Puller Ass'y: TLU-90901-05-20 (U.S.A.)
1. 3-WayPuller: 90890-01848
2. 3-WayPuller Attachment: 90890-01803
3. 3-WayPuller Attachment: 90890-01804
4. 3-WayPuller Screw: 90890-01906
5. Drive handle: 90890-01817
4. Remove the woodruff key from the
crankshaft. Remove the
two securing
screws and remove the coil plate.
5.
For inspection, refer to 6-1, G "Pulser
and Charge
Coil.",

C. Oil Pump
Plunger
Adjusting Pulley
1. Loosen the four gear-case bolts, and
remove
the gear case/oil pump assembly
from
the engine.
2. Remove
the two gear case screws and
open the gear case.
3. Remove
the snap ring and the two
washers, and remove the drive gear. Note
the relative positions of the washer. The
wave washer is against
the drive gear.
4. Rotate
the oil-pump drive shaft until the
securing pin is opposite the slot in the
gear case. Remove the pin and remove
the pump from the gear case.
~ @~ Oil Pump Drive Shaft
~
5. Remove the drive shaft from the oil
pump. Inspect
the bearing surfaces of
the shaft and the gear teeth. If any part
of the shaft is worn or pitted, the shaft
must be replaced.
The oil pump should not be disas-
sembled unless the pump stroke must be
checked. If a problem with
the pump is
noted (such as excessive oil consump-
tion) proceed as follows:
6. Remove
the oil pump cover.
2·4

7. Check the minimum pump stroke.
a.
Turn the oil pump gear until the plunger
is at its maximum distance from the
pump body.
b. Using a feeler
gauge, measure the gap
between the adjusting plate and the
raised bosson the adjusting puIley.
Minimum pump stroke:
0.2'" 0.25 mm (0.08'" 0.010 in)
1. Oil pump gear 2. Plunger 3. Minimum pump stroke
8. Measure the maximum pump stroke.
a. Pull the oil pump cable
out of its sheath
as far as
it will go. The cable must be
held in this taut position when measur-
ing maximum pump stroke. It may be
helpful to securely wrap
duct tape
around the cable where
it enters the
sheath.
b. Turn the oil pump gear
until the plunger
is at its maximum distance from the
pump body.
c. Using a feeler
gauge, measure the gap
between the adjusting plate and the
raised bosson the adjusting pulley.
Maximum pump stroke:
1.65 -- 1.87 mm
(0.065'" 0.074 in)
1. Oil pump gear 2. Plunger 3. Maximum pump stroke 2-5
9. If either the maximum pump stroke or
the minimum pump stroke does
not
equal specification, remove the adjusting
plate and add or remove adjusting shims
as required. Adding shims
increases the
stroke, removing shims
decreases the
stroke.
1. Adjusting shim
1 O. Reinstall the adjusting plate and lock
nut. Torque the
nut to specification.
Recheck maximum and minimum pump
stroke.
Tightening torque:
0.67 m-kg (4.8 ft-lb)
11. Grease the adjusting plate, and reinstall
the oil pump cover.
Seal the cover with
Yamabond 5. Torque the screws to
specification.
Tightening torque:
0.2 m-kg (1.45 ft-Ib)

...Denotes a revision. Please remove and destroy the original page, and insert this revision page in its place.
D. Top End
This model has a one-piece
cylinder and
cyl inder-head assembly. There is no
cylinder
head to remove and service separately from
the cyl inder.
Cylinder
Disassembly
1. Loosen
the spark plug, and remove the
cyl inder from the crankcase.
2. Cover the crankcase
with a clean rag so
nothing will accidently drop into the
crankcase.
3. Remove a piston
pin cIip from the
... piston, and remove the pin with the
universal piston-pin puller.
Universal piston-pin puller:
YU-01304
MS623 BR250F Service Manual Revised 1/82
2-6
~ Cvlinder Bolt
Piston Pin CIip
4. Remove the piston and the small-end
bearing
from the connecting rod.

Inspection
1. Piston
pin and bearing inspection.
a. Check the piston pin
for signs of wear.
If any wear is evident, replace the pin
and the bearing.
b. Check the
pin and bearing for signs of
heat discoloration. If excessive (indenta-
tion on pin, etc.), replace the pin and the
bearing.
c. Check the small-end bearing
for exces-
sive wear or damage. Check the rollers
for signs of flat spots. If such wear is
found, replace the pin and the bearing.
d.
Apply alight film of oil to the pin and
bearing surfaces. Install them in the
connecting rod small end to inspect
for
wear. Check for play. There should be
no noticeable vertical play.
If play exists,
check the connecting rod small end
for
wear. Replace pin, connecting rod and/
or bearing, asrequired.
2-7
e. The piston pin should have no noticeable
free play in the piston.
If the piston pin
is loose, replace the pin and/or piston.
2. Piston
a. Remove the piston rings.
b. Removeany carbon deposits from piston
crown.
c. Carefully remove any carbon deposits
from the ring grooves.
d. Hernove score marks and lacquer
deposits from the sides
of the piston
using 600 -- 800
grit wet sandpaper.
Sand in a crisscross pattern. Do
not sand
excessively.

e. Wash the piston in solvent, and dry it
with compressed air.
f. Measure the outside diameter
of the
piston at
the piston skirt.
The measurement shouId be made at a
point 10 mm (0.39 in) above the bottom
edge of the piston. Place the micrometer
at a
right angle to the piston pin.
The
maximum piston diameter subtract-
ed
from the minimum cylinder diameter
gives
the piston clearance. If the clear-
ance is beyond tolerance, hone the
cylinder to tolerance or bore it to the
next oversize and install an oversized
piston.
Piston clearance:
Minimum 0.045 mm (0.0018 in)
Maximum 0.050 mm (0.0020 in)
Piston oversize:
70.25 mm (2.766 in)
70.50 mm (2.776 in)
1. 10 mm (0.39 in)
2-8
3. Piston rings
a. Check the rings
for scoring. If any severe
scratches are noticed, replace
the rings as
a set.
b. Measure the ring end gap in the un-
installed rings.
If it is beyond tolerance,
replace the rings asa set.
Ring end gap, free:
Approx. 6.5 mm (0.26 in)
c. Push the ring
into the cylinder, and
measure the ring end gap
with a feeler
gauge. Push
the ring into the cylinder
with the piston crown so the ring will be
at a right angle
to the cylinder bore. If
the end gap is not within specification,
replace the rings asa set.
Ring end gap, installed:
Minimum 0.20 mm (0.0079 in)
Maximum 0040 mm (0.0157 in)

4. Cylinder
a. Remove all carbon deposits from the
cylinder and from the ports. Carburetor
cleaner
will help lift carbon from the
cylinder head. Thoroughly wash the
cylinder in solvent, and blow
it dry with
compressed air.
b. Inspect the cylinder walls
for scratches.
If vertical scratches are evident, the
cylinder should be rebored or replaced.
c.
Measure the cylinder wall wear at the
places shown in the illustration; use a
cylinder bore
gauge. If wear is excessive,
compression pressure will decrease; re-
bore or replace the cylinder.
----------
Standard Wear limit
Cylinder bore
70.00 ......, 70.02 mm 70.05 mm
(2.756
-2.757 in) (2.776 in)
Cylinder taper
0.05mm
(0.002 in)
Cylinder out-of- 0.01 mm
round -(0.004 in)
"~-'-
,,~ ~~
....... ------_...-....,.......,.,..
Boring
If the cylinder requires boring, follow the
standard boring procedures
but use an offset
bit as shown below. This bit is standard
equipment
with some boring bars. Be sure
that the depth adjustment is precisely set so
the combustion chamber is
not damaged.
Honing
Whenever honing the cylinder on the BR250,
usea hone
with a bumper device sothe com-
bustion chamber
will not be carelessly
damaged. Otherwise
follow standard honing
procedures. Yamaha recommends the use
of
an Ammco Hone. This kit includes all the
necessary piecesto properly hone the cylinder
on the BR250.
Ammco Hone
Kit: TLU-03950-00-00