Worn Out; Preignition; Checking Ignition Timing; Adjusting Ignition Timing - Polaris 1999 Sportsman 400 Service Manual

LU BRICATION, MAINTENANCE AND TUNE-VI'
89
'Jl o rll out
Corrosive gase s formed by co mbustion and high
voltage spa rks have ero ded the elect rode s.
A spark
plug in this condition req uires more vo ltage to fire
under hard acceleration. Rep lace w ith a new spark
plu g.
Preignition
If the electrod es are melt ed, pre ignition is a lmost
ce rtainly the cause. Chec k for inta ke leak age and
over-advanced ignition timing. It is also possible
that a plug ofthe wrong heat range (too hot) is being
used. Find the ca use of the preig nition be fore re-
turn ing the engi ne to service. For additio nal infor-
mation on preignition, refer to Preignition in
Chapter Two.
NOTE
Because ig nition components are tem-
perature-sensitive, check ignition tim-
ing while the engine is cold. Timing
may change as much as
2°
when the
eng ine warms.
I. Place the ATV on a level s urface and apply the
parking brak e. Block the wheels to keep it from roil-
ing in e ither direc tion .
2.
Remove the plug from the tim ing hole in the re-
co il star ter cover ( Figu re 78).
3. A ttac h a stroboscopic timing light to the spark
plug lead foll ow ing the manu facturer' s instru c-
tions.
4 . Attach a po rtable tachom eter acc ording to its
manufacturer 's instruction s.
5. Shift
the transm ission to NEU TRAL.
WA RNING
Do not allow anyone to stand behind
or infront of the vehicle when the en-
gine is running. Keep hands, feet and
cloth ing awa.v from the engine, helt
and drive chains.
6. Start the engine, allow it to idle for approx i-
mately
10- 15
seco nds, then increase the engin e
speed to the ignition timi ng spe ed rpm listed in Ta-
ble 5
7.
Po int the timing light at the reco il starter cov er
timin g insp ection hole (Figu re 78) and observe the
flywhee l tim ing mark.
II
C hecking
Ignition Timing
All mode ls are equi pped with a capaci tor dis-
charge ignition (COl) an d no breaker points are
used. Thi s ign ition system is muc h less susc eptible
to failures ca used by dirt , mo isture a nd we ar tha n
brea ker-point ignition systems.
Change ignit io n timi ng by relocating the stator
plate located under the enginc llyw hee i. When dis-
assembling, note that the ho les for the stato r plate
attac hing screws are elo ngat ed.
\Vhen assemb ling the stator plate, a lign the mark
on the stato r plate w ith the mark on the cra nkcase as
shown in Figu re 9 1. It may be neces sary to mo ve
the stator plate slightly when timi ng as de scribed in
this chapter.
NOTE
The timi ng light willflash, appearing
10
stop
the
timing marks at the instant
ofignition.
R.
Increase the engi ne speed br iefly
and
o bserve
the timing mark that is aligned w ith the timing
pointer (Figure 92) .
9. If timing is not correct , adj ust it
as
desc ribed in
the fo llow ing proc ed ure .
10.
W he n tim ing is correc t, turn the engine o ff, re-
mo ve the tim ing light and tachometer. Insta ll all of
the cov ers that were remo ved.
Adjusting Ign ition T im ing
The ign ition must occur at a specifi c tim e to
achi eve optimum engin e performanc e.