(Ii)Poor Idle Speed Performance; (Iii) Poor Middle And High Speed Performance; (Iv) Shifting Troubler - ATV 250 Service Manual

( 2 )Piston and piston ring
.Improper piston ring installation
.Piston ring is worn and out of elastic-
ity
.Piston is damaged or crack
( 3 )Valve, camshaft and crank shaft
.Valve didnt closed entirdly
.Improper match between valve and valve
seat
.Wrong port timing
.Valve spring is damaged
.Valve camshaft is damaged
.Crank shaft is damaged

(II)Poor idle speed performance

(1)Carburetor
.Starting plug is not close entirely
.Idle metering jet is loose
.Idle metering jet is clogged
.Idle air metering jet is clogge
.Improper idle adjustment
.Leakage of carburetor
(2) Electric system
.Spark plug is bad
.CDI is bad
.Coil is bad
.Charging coil is bad
.Ignition coil is bad
(3)Valve system
.Improper adjustment of valve clearance
.Core of air filter is clogged
(III)Poor middle and high speed perfor-
mance
Refer to "starting trouble/difficulty"and poor
idle speed performance section in this chapter.
(1)Carburetor
.Wrong needle valve position
.Main jet is clogged or loosened
.Fuel is deteriorated or polluted
.Wrong float chamber oil level
(2)Air filter
.Core of air filter is clogged
(IV)Shifting trouble
1.Shifting difficulty
Refer to "slippig of clutch"and "ablation of
clutch"in this chapter
2.Shifting pedle is clogged
(1)Shifting shaft groups
.Shifting shaft is bend
.Shifting lever groups is damaged
(2)Shifting cam, shifting fork
.There is foriegn matter in shifting cam-
shaft recess
.Shifting fork is clogged
.Shifting fork shaft is bend
(3)Driving system
.Driving gear is clogged
.Foreign matter is clogged
.Incorrect driving system installation
3.Shift is out of gear
(1)Shifting shaft groups
.Improper adjustment of limited lever
postion
.Limited lever can't back
(2)Fork
.Fork is worn
(3)Shifting cam
.Recess of shifting cam is worn
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