Yamaha RD250 User manual

MODEL GUIDE
PREStrNTATION Dtr MODtrLtr
MODELLANLEITUNG
90894- 09025

NOTE: INFORMATION AND OTHER TECHNICAL DATA (tNCLUDtNG SpECtFtCAT|ONS) tN THtS
MODEL GUIDE MAY BE SUBJECT TO CHANGE WITHOUT PRIOR NOTICE.
A. FEATURES
@urcur pERFoBMANcE ENGTNE wtrH
_ NEW CYLINDER
- NEW EXHAUST MUFFLER
- c.D.t.
_ BIGGER CARBURETOR
@sorr roucH opERATtoN oF cHANGE eEDAL
@cnsrrruc wHEEL wtrH BLAcK coATtNG
@serren RTDTNG posrrroN wtrH NEW HANDLEBARS
AND FOOT RESTS
I.D. & ENGINE/FRAME NUMBER
MODEL NAME l.D. Nos, E/G STARTING Nos. AREAS
RD250 2R8 1A2-220101 A, B, DK, NL, CH, UK
RD25O 2TO 1A2-310101 D
RD25O 2T'l 2T1-000101 F
R D4OO 2R9 143-110101 A, B, DK, UK, SF, D, NL, S, CH
RD4OO 2T2 2T2-OOO101 F
I
f,_

B. DIFFERENCES FROM 1977 MODEL
MODIFICATION
IENGINE SECTION]
1. Kick starter has been changed from the ratchet
REMARKS
Better function
Easy operation
c
type to the Bendix type.
ry
Primary driven geer width has been reduced.
e
e
t
A dimension: 15 mrn-12 mm
Carbu retor
a. Synchronizationport
a
-2-

MODIFICATION
b. Carburetor setting
RD25O ,77 MODEL ,78 MODEL
MODEL VM28SS <-
I,D. No. 1 5200 2 R800
MJ # 115 <_
AJ 1.0 0.8
JN 5L3-2 5L1-4
NJ o-8 o-6
CA 2.5 2.O
AS 1% <_
GS #70 <-
NOTE: The above specification may be changed without
prior notice.
RD4OO '77 MODEL ,78 MODEL
MODEL VM28SS <-
l.D. No. 14300 2R900
IVIJ # 120 # 145
AJ 0.5 <-
JN 5L1-3 5J6-3
NJ P-2 o-8
CA 2.5 <-
PJ 25 <-
AS 1% <_
GS #70 <_
NOTE : The above specifications may be changed without
prior notice.
For better engine performance the shape of
transfer port and inlet port timing have been
changed.
RD25O
REMARKS
Easy engine setting
t
t
Qr
|r)r
N
Or
tt
\- +'
@ lnlet port
@ E"harst port
@ Scauenging ports
- (Transfer)
PORT TIMING (MM}
,77 MODEL ,78 MODEL
A 29.5 <-
B62.5 665

MODIFICATION
C tntet port
@ Exhaust port
@ Scauenging ports
(Transfer)
REMARKS
Due to change of inlet
port timing
Better engine
perf ormance
ru
5. MANIFOLD (For RD400 ON LY)
For better engine performance, both right and
left manifolds are provided with balance pipe. t
t
t
7have been
t
PORT TIMING (MM)
77 MODEL ,78 MODEL
A33.5 <_
B395 41 5
c640 68.5
nn
oo
trN
ocn
oo
ffiffi.)
PISTON (For RD400 ONLY)
Change in shape
EXHAUST PIPE & MUFFLER
Both inside diameter and volume
changed.

I
\,
\,
b
ty
MODIFICATION
IELECTRTCAL SECT|ONI
1. Modification of lgnition system
Battery lgnitio
2. lgnition coil 2 coils- 1 coil
3, Voltage regulator and rectifire
Separate type ..------ lntegrated type
C.D.l. lgnition timing adjustment procedures.
C.D.l. lgnition
1. lnstall dialgauge to left side spark plug
hole.
2. Rotate crankshaft countrclockwise up
to T.D.C. and slowly turn it clockwise
until dialgauge indicates the specified
spark advance position.
R D250 BTDC 2.00 l- 0.1 5 mm
R D400 BTDC 2.30 1 0.1 5 mm
3. At this time, adjust magneto base
using screw driver until both marks
(lF, l) become alignment.
REMARKS
Better engine
performance
Not interchangeable
Due to use of CDI
Prevention of plug
from coming off
4. Spark plug cap with rubber ring.
Screw driver
lry Rubber ring

TN
00
AN
ou
oo
MODIFICATION REMARKS
IFRAME SECTION]
1. Caliper Ass'y (Front & Rear)
Change of operation method
Fixed caliper type-----> Floating caliper type
(Tow pistons)
2. Front fork Ass'y
Fork Travel
lnner tube
diameter
(One piston)
t
120 mm------->140 mm
344 ------------> 354 t
3. Better riding comfort due to change in riding
position by changing the mounting position of
handlebars and footrests.
POSITION ,77 MODEL ,78 MODEL
@570 mm 576 mm
G) 202 196
@500 500
o199 224
o00 e:30'

C. GENERAL SPECIFICATION
D. SERVICE DATA
\',
v
\,
lv
RD25O RD4OO
DCH, DK. F
UK, NL, ABD, CH, SSF, DK, F
UK, NL, A, IB
DIMENSIONS/WEIGHT
Overall length
Overall width
Overall height
Wheelbase
Minimum ground clearance
Machine net weight
2,030 mm
760 mm
1,060 mm
1,320 mm
150 mm
172 kg
2,015 mm
(CH. DK)
1,995 mm
(UK, NL)
<-
<-
<-
145 mm (CH,
DK, UK, N L, D,
F)150 mm (A)
170 kg (CH, DK)
172 kg lF , UK,
NL, A}
1,955 mm
(F, A, B}
<-
<-
<_
1,325 mm
'I 5O mm
170 ks
2,030 mm
<-_
760 mm
1,060 mm
1,320 mm
'l 5O mm
174 kg
2,Ol 5 mm
(DK)
1,995 mm (F,
NL, UK, I, A}
<_
<:
<-
<-
172
174 ks (DK)
kg
1,995 mm
<-
<-
1,325 mm
<_
174 ks
ENGINE
Type
Bore/Stroke
Displacement
Compression ratio
Starting svstem
Lubricating system
2 cycle aircooled
54x54
247 cc
N,A
Kick starter
Automatic
separate
<_
<-
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6,2 <_
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64x62
398 cc
6,2
<:
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CLUTCH
Type
Primary drive system
Primary drive ratio
Wet multiple
disk
Gear
6A121
<-
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Gear
66123
<_
<-
<_
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<-
TRANSMISSION
Type
Reduction ratio 1st
2nd
3rd
4th
5th
6th
Constant mesh
36114
32118
29122
26124
25126
24127
<-
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SECONDARY DRIVE
Type
Reduction ratio Chain
38117 <_
<_. <-
36117 <-
35/17 <-
<- <_
361't7
ELECTRICAL
lgnition type c.D.t. <- <- <- <- <-
c
r
o
C
o
CARBURETION
Type
Effective venturi size
Main jet
Needle jet
Jet needle
Air screw (Turns out)
Cut away
VM285S
28
#tts
o-64
5L14
't%
2.O
<-
<--
<_
<-
<_
<-
<-
<-
<:
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<-
<_
<-
<-
vM28SS
28
#tqs
o-8
5J6-3
1%
2.5
<-
<-
<_
<-
<-
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<_
<-
<:
<_
<-
<-
VOLUMES/TYPE FLUID
Gasoline tank
Transm ission 16.5 e
1.5 e <-
<_ <-
<_ 16.5 e
1.5 e <_
<_ <_
<-
\-
-7-

MEMO
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oo
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YAIYIAHA MOTOR (C(O., LTD, Y
PRINTED IN JAPAN
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(4.1/^)
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