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signed to g ive th e YZ m ore power o n
to p ; i t is a producti on versi on of
m od ifi ed stoc k pi pes th e works Yama ha rider u sed early last year. T he
p ipe exi ts th e cyli nder th roug h a center p ort a nd wo r ks its way a lo ng th e
righ t side o f th e mo torcycle, where a
new a lu min u m silencer is a ttached to
the end. T he silencer's co re is no w
mad e o u t o f steel ra th er th an th e
a lu mi n u m th at u sed to break a pa rt as
soon as th e packing blew o u t.
T he ro un d-s li de 38 m m Mikuni
ca rb ura ror is ba sicall y the sa me as
la st year's with th e exce p tion of usin g
a choke lever ins tead of a kn ob for
easier access.
Fitted inside the cy li nder's inta ke
cham ber is a new single-s tage fib er
reed va lve (vs. stee l) to g ive th e Yama ha be tter thro tt le response a t low
rpm.
T he five-speed trans missio n is unchanged, bu t th e fina l d rive ra tios are
d ifferent - both fr ont a n d rear
sprocke ts are on e tooth la rger to help
kee p th e chai n from rid in g o n th e
sw ingarm , a nd to reduce.the chai n's
bend around the co u n ters haft sp roc ket, wh ich helps prolong the lif e of th e
chai n.
Two needl e ro ller beari ngs, (in stea d o f o ne), are now used in th e
cl u tc h ac t ua t i ng ar m's pivo t,
i m p rov in g clutch lever feel. Th e we t
multi-d isc cl u tch remai ns the sa me .
T he Yamaha 's ig n ition sys tem is
a ll new fo r '85 - it 's like th e ignition
used on la st year's YZ60 a nd o n the
works bikes; however, the one used
o n th e 250 is slig h tly m odi fied. T he
flywh eel is no longer a so lid uni t; it 's
mou nted interna llv wi th in th e left
case a nd is ga urdedby a pl a sti c cover.
O ne p robl em YZ ow ner faced la st
year was radiator breakage, especia lly
on the right because th e mo u n ts
cracked . Th is vear th e mo u nts h ave
bee n beefe d u p' co nsidera bly.
For easier access to th e a ir filter, th e
bracket securing th e element wa s
shorte ned - i t used to be d ifficult to
pu ll th e fil ter o u t o f th e box wi thou t
bendi ng a nd squeezi ng the singlestage foam element , Si nce the bracket
is no w s hor ter, th e wingnut hol d in g
th e filt er to th e bracket is lon ger.
T he red-pai nted , chrome -mo ly
frame is n ow lighter a nd stro nger
tha n befo re, because th e tubing wall
t hic k ness is re duced ( 1.8 m m to
1.6mm), ' a nd t he -Ira m e- ru be -j uno- >
tions h ave been rei nforced wit h more
gussetti ng. It has a si ngle front down tube th at sp lits in to a dou ble-cradle
w here th e ex ha ust pipe mee ts th e
cyli nder. Basic frame geometry is
u n ch an ged : Wh eel base is 57.9 inc hes,
sea t h eight 38 in ch es an d groun d
cleara nce 13.4 inches.
Th e single-s hock rea r suspens io n
linkages are a lso the same, but the
Ka yab a shock went th rough va lving
cha nges to accept th e Brak e Actua ted
Suspension Sys te m (B.A.S.S.), designe d to eli m ina te axcessive backend ho p whe n brak in g for turns.
T here is a small ca ble running fro m
the rear brak e peda l to th e shock's
reservoir; wh en the rear brak e is applied (a nd weight transferr ed of f the
rear wheel), th e shock's compression
da m p in g is red uced by 9- 11%. The
B.A.S.S. system varies th e a mou nt o f J
p reload o n the ba se va lve's blow-off
spri ng to a lter da mpi ng rates, so
whe n th e back w heel slams in to a •
bu mp with th e br ak e o n , th ere is less
compression dam ping and thus less
rear wheel kick.
Externa l!y-adj ustable o n th e shock
a re 25 rebound a nd 28 co m pressio n
da m ping setti ngs, p lus full y-ad ju stable p rel oa d. Wheel tr avel is 11 .4
inches .
U p fro n t, th e 43m m Ka ya ba fo rk
use 30mm less a nd heavier weight oi l,
while whee l trave l remains the
sa me a t 1!. 8 in ch es. Locat ed a t th e
bottom of each fo rk leg are compression damping adjusters, each with 16
setti ngs. T he sta nc hion tubes are protected by red fork boo ts; th e sliders are
un protected .
New th is year is th e fro nt hyd ra ul ic
disc brak e with a brai ded stai n less
stee l h ose; th e d isc is 3m m thi ck , 9.4
inc hes in diameter a n d is drilled o ut
to save weight , It has a dual-pisto n,
single-ac tion hydra ulic ca liper wi th
sem i- me ta ll ic br ak e pads. The rear
br ak e is handl ed by a single- lea ding
drum o pe rated by a no n -foldi ng brake
pedal a nd a straig h t-pu ll ca ble.
Both fron t an d rear gold -an nodized
rims are stronger this year - they 're
so lid rather tha n h oll o w Ta kasago
rim s (D. L D . rim s we re u sed in '84) ,
a nd the Z-spokes are 0.5mm larger
with steel n ip pl es ins tead of al umi n u m . Tires are made by Bridgeston e,
La st yea r, m an y riders co m p lai ned
th at th e sea t ,was. too so ft a nd had a
deep 'slo m}j at ' the' tank j u nction:
