Power Train; Low Engine Operating Speed; Engine Operating Speed Too High; Engine Speed Erratic During Speed Or Load Changes - Polaris 1999 Sportsman 400 Service Manual

48
®
LEAKDOWN TESTER
C IIA I' TER TWO
To air compressor
Supply pressure
Cylinder pressure
4. Rem ove the spa rk plug ca p and the spa rk plug as
described in Chapt er T hree.
sots
The engine mny ' urn (weI' when air
pressure is applied to the cylinder. To
prevent this fro m happening , shift tire
low range and set the parking brake.
5. Install the leakdown tester into the cy linder
spa rk plug hole ( F ig ure 18).
6. Apply pre ssur e to the cy linder following the
manufacturer 's instru ctions, Listen for air lea king
w hile noting the fo llowing:
a. Air leaki ng throu gh the exhaust pipe indi-
ca tes a leaking ex haust va lve .
b. Air leaking thro ugh the carburetor or throttl e
body indicates a leaking inta ke valve .
c. A ir leaking through the crankcase breather
tube indica tes wo rn pisto n rings.
7. A cylinder w ith 10%1 cylinde r Icakdown req uires
furt her se rvice.
8. Install the spark plug and the air filter as sembly.
POWER TRA IN
Th e fo llow ing items provide a sta rting point from
whic h to troublesh oot pow er tra in mal function s.
Th e possibl e cau ses for eac h malfunct ion are listed
in a logical sequence .
Low Engine Operating Speed
(E ngine Running Properly, but Lugs)
1. Drive pulley spring is bro ken or wrong spring.
2. Drive pull ey we ight is
100
hea vy.
3. Drive belt is slipping.
E ng ine Operating Speed Too Hig h
I. Inco rrect dri ve pull ey spring.
2. Drive pull ey we ights arc too lig ht.
3. Drive pulley is binding.
4 . Driven pulley is bind ing.
E ngine Speed Erratic
During Sp eed or Loa d Changes
I. Drive pu lley is binding.
2. Driven pull ey is binding.
3. Pulley grooves arc worn.
Ha rsh Engage ment
I. The drive be lt is worn (too narrow) .
2. Inco rrect pull ey-to-pu lley cl earance ( 1996- 1998
model s).