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10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-0
Mongoose/KXR 250
10
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FINAL REDUCTION/TRANSMISSION SYSTEM
__________________________________________________________________________________
SERVICE INFORMATION -------------------------------------------- 10- 2
TROUBLESHOOTING ------------------------------------------------- 10- 2
TRANSMISSION CASE COVER------------------------------------------ 10- 3
TRANSMISSION-------------------------------------------------------- 10- 5
10
Page 2
10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-1
Mongoose/KXR 250
Page 3
10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-2
Mongoose/KXR 250
SERVICE INFORMATION
GENERAL INSTRUCTIONS
• The transmission system can be serviced with the engine installed in the frame.
• When replacing the drive shaft, use a special tool to hold the bearing inner race for this operation.
SPECIFICATIONS
Specified Oil: GEAR OIL SAE 90#
Oil Capacity: At change : 0.3 liter
At disassembly : 0.4 liter
TORQUE VALUES
Transmission case cover bolt 2.4_ 3.0kgf-m
TROUBLESHOOTING
Engine starts but motorcycle won‘t move
• Damaged transmission
• Seized or burnt transmission
Oil leaks
• Oil too rich
• Worn or damaged oil seal
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10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-3
Mongoose/KXR 250
TRANSMISSION CASE COVER
REMOVAL
Drain transmission gear oil into a clean
container. (Refer to the “TRANSMISSION
OIL REPLACEMENT” section in the
chapter 3)
Remove the three and then remove the drive
sprocket cover.
Remove the two bolts and then remove the
washer and drive sprocket.
Remove the bolt and then disconnect the
drive shift arm from the shift shaft.
Remove the transmission case cover attaching
bolts.
Bolts
Drive Sprocket
Bolts
Drive Sprocket Cover
Select Arm
Bolt
Bolts
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10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-4
Mongoose/KXR 250
Remove the transmission case cover, dowel
pins and gasket.
Inspect the bearings for allow play in the
transmission case cover or the bearings turn
roughly.
If any defects are found, replace the bearing
with a new one.
TRANSMISSION CASE COVER
DISASSEMBLY
Remove the drive axle circlip.
Remove the drive axle from the transmission
case cover.
Remove the bearing circlip for remove the
bearing.
Inspect the bearing for allow play in the
transmission case cover or the bearing turns
roughly .
If any defects are found, replace the bearing
with a new one.
Inspect the drive axle gear teeth for wear or
damage.
Remove the bearing to expose the oil seal.
Inspect the oil seal for wear or damage.
If any defects are found, replace the oil seal
with a new one.
Transmission Case Cover
Bearing Circlip
Drive Axle Circlip
Drive Axle
Bearing
Oil Seal
Bearings
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10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-5
Mongoose/KXR 250
Inspect the needle bearing for allow play in
the transmission case cover or the bearing
turns roughly.
If any defects are found, replace the bearing
with a new one.
ASSEMBLY
Install the needle bearing.
Install the oil seal and bearing.
Install the bearing circlip.
Install the drive axle and drive axle cirelip.
TRANSMISSION
REMOVAL
Remove the transmission cover. (Refer to the
“TRANSMISSION CASE COVER REMOVAL” in
the chapter 10)
Check the transmission operation.
Unsmooth operation _ Repair.
Remove the shift shaft.
Needle Bearing
Needle Bearing
Bearing
Shift Shaft
Page 7
10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-6
Mongoose/KXR 250
Remove the stopper plug.
Remove spring, washer and shift cam
stopper.
Remove the transmission guide bar.
Remove shift cam.
Shift Cam Stopper
Washer
Spring
Plug
Plug
Guide Bar
Shift Cam
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10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-7
Mongoose/KXR 250
Remove the shift fork.
Measure the guide bar runout.
Out of specification _ Replace.
Service Limit: Less than 0.03 mm
Inspect the shift fork cam follower and shift
fork pawl.
Scoring/beads/wear _ Replace.
Check the shift cam groove and shift cam
gear.
Wear or damage _ Replace.
Shift Fork
Do not attempt to straighten a bent guide
bar.
°Ø
Shift Fork Cam Follower
Shift Fork Cam Pawl
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10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-8
Mongoose/KXR 250
Inspect shift shaft gear.
Damage _ Replace.
Inspect shift shaft.
Damage/bends/wear _ Replace.
Remove the main axle.
MAIN AXLE DISASSEMBLY
Remove the washers, collar, primary driven
gear, bush and clutch dog.
Shift Shaft Gear
Shift Shaft
Main Axle
Collar
Washer
Primary Driven Gear
Clutch Dog
Washers
Primary Driven Gear
Clutch Dog
Collar
Main Axle
Bush
Page 10
10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-9
Mongoose/KXR 250
Remove the circlip and then remove the
washers, reverse wheel gear and needle
bearing.
Inspect the gear teeth.
Blue discoloration/pitting/wear _ Replace.
Inspect the mated dogs.
Rounded edges/cracks/missing portions
_ Replace.
Circlip
Washer
Reverse Wheel Gear
Washers
Circlip
Needle Bearing
Reverse Wheel Gear
Main Axle
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10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-10
Mongoose/KXR 250
MAIN AXLE ASSEMBLY
Reverse the “MAIN AXLE
DISASSEMBLY” procedures.
Washer
Circlip
Needle Bearing
Reverse Wheel Gear
Main Axle
Washer
Primary Driven Gear
Clutch Dog
Collar
Bush
Washer
Washer
Washer
Page 12
10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-11
Mongoose/KXR 250
Remove the counter axle.
Inspect the gear teeth.
Blue discoloration/pitting/wear _ Replace.
PRIMARY DRIVE AXLE REMOVAL
Remove the clutch/driven pulley. (Refer to
the chapter 9)
Remove the oil seal, circlip, screw and plate.
Remove the primary drive axle.
Inspect the bearings for allow play in the
transmission case cover or the bearing turns
roughly.
If any defects are found, replace the bearing
with a new one.
Counter Axle
Bearings
Bolt
Primary Drive Axle
Plate
Circlip
Oil Seal
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10.FINAL REDUCTION/
TRANSMISSION SYSTEM
10-12
Mongoose/KXR 250
INSTALLATION
Reverse the “TRANSMISSION REVOVAL”
section procedures.
Install the primary drive axle. (Reverse the
“PRIMARY DRIVE AXLE” procedures.)
Install the counter axle.
Install the main axle.
Install the shift cam.
Install the shift fork.
Install the guide bar.
Install the shift shaft.
Install the shift cam stopper and tighten the
plug.
Torque: 4.5_ 5.0kgf-m
Install the dowel pins and a new gasket onto
the right crankcase.
Install the transmission case cover and tighten
the transmission case cover bolt.
Torque: 2.4_ 3.0kgf-m
Fill the engine with oil and install the oil filler
bolt. (Refer to the “TRANSMISSION OIL
REPLACEMENT” section in the chapter 3)
Specified Gear Oil:
KYMCO SIGMA GEAR OIL 90#
Oil Capacity:
At disassembly : 0.4 liter
At change : 0.3liter
Gear Change Switch
Dowel Pins
Gasket
Make sure that the lever on the gear
change switch correctly engages with the
locating slot on the shift shaft.
Align the mark on the shift shaft gear
with the mark on the shift cam gear.
°Ø
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