Drive Pulley; Fixed And Sliding Pulley Halves; Drive Pulley Spring; Eng Ine No Ises - Polaris 1999 Sportsman 400 Service Manual

CL UTCH/DRIVE BELT SY STEM
Tapered surfaces
ment spee d. Wh en the engi ne is at idl e speed and the
vehicle is stopped, the one-wa y clu tc h freewh ee ls
on the dri ve clutch shan.
DRIVE PU LL EY
Fixed a nd Sliding Pulley Halves
The sides of the pu lley are made of mild steel and
the be lt co ntac t surfaces are precision ma chined to a
smo oth taper. The pull ey is carefully bal an ced to
prevent vibration. Th e taper ed surfaces of bot h
pulp
leys match the V-be lt grip ping surface (Figure 3) .
The d rive pulley assembly is mou nted on the le ft
end of the engine cranksha ft. When the engi ne is at
idt e or stopped, the fixed and sliding halves of the
pull ey are held apart by the primary spring . At idl e
speed or when the engine is stopped. the groove
should be wide eno ugh for the V-helt to drop down
between the sides of the pulley w ith no engagement.
There is no engag ement beca use the w idth of the
be lt is less than the space between the sides of the
dri ve pu lley.
Wh en the engine speed is increased from idle,
centrifugal force causes the weight levers mo unted
on the slid ing half of the drive pulley to sw ing out.
When the centrifugal force of the weights is suffl -
cient to overcome the pressure of the primary
spring, the slid ing hal f of' thc pu lley is mov ed closer
21 5
to the fixed ha lf. T his movement narro ws the
groove betw een the pu lley halves until the sides of
the pull ey gr ip the be lt. The po int at whieh the pu l-
ley gr ips the belt is ca lled the engagement rpm . En-
gagement rpm wi ll occur at approxi mately 150 0
eng ine rp m. A t low spee d, the belt wi ll be located at
the lo w-s peed posi tion as s hown in Figure 2.
As eng ine spee d incr eases, centrifuga l fo rce
causes the weights of the d rive pull ey to sw ing fur-
ther ou t and forc e the slid ing half of the pull ey
closer to the fixed ha lf. As the groove of the dri ve
pulley beco me s narrowe r, the V-belt is force d up -
ward in the groove toward the outer edge o fth e pu l-
ley. T he V-be lt is forced deeper into the groove of
the dr iven pu lley as ind icated by the high -speed po-
sitio n of the belt in Fig u re 2.
Thou gh not part of the dr ive pu lley, it s hould be
noted that the release (secondary) spring o f the
dr iven pull ey forc es the sides of the pulley together.
Pre ssure aga inst the sides
of
the driven
pulley will
force the slidi ng hal f away from the fixed side .
Mo vement of the weig ht levers in the dri ve pulley
will force the pulley halves together and the belt
wi ll mo ve to the o uter diam eter of the drive pulley.
At the same time the be lt wi ll force the sides of the
dri ven
pulley apart so
that it ca n oper ate deeper
in
the groo ve .
Drive P ulley S p r ing
T he d rive pulley clutch releas e spring cont rols
engage ment speed.
If
a lighter spring is instal led, or
the weights ar e too hea vy, the dri ve
will
up -sh ift too
fast and the engine will no t be able to renc h its oper-
ating range
of 6000
rpm.
If a
heavier spri ng is in-
stalled, the eng ine speed m ust be high er to
overcome spring pressure and allow engagement. If
the spring is too stiff or the weights too heavy, the
drive w ill not be abl e to move high eno ugh in the
pulley groove to attain high gear. Refer to Table 2
for the o rig inal spr ing install ed on the specific
model and year being work ed o n. Table 3 lists spe c-
ifications for iden ti fying the different springs. Ac -
tual performance depend s upon a co mbination of
cha rac teristics, but genera lly. the springs arc listed
in Table 3 from the strongest at the top to the weak-
est at the bottom of the table .