11.CRANKSCASE/CRANKSHAFT/
BALANCE SHAFT
11-0
Mongoose/KXR 250
11
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CRANKCASE/CRANKSHAFT/BALANCE SHAFT
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SERVICE INFORMATION -------------------------------------------- 11- 2
TROUBLESHOOTING ------------------------------------------------- 11- 2
CRANKCASE/CRANKSHAFT/BALANCE SHAFT----------------- 11- 3
11
11.CRANKCASE/CRANKSHAFT/
BALANCE SHAFT
11-1
Mongoose/KXR 250
11.CRANKSCASE/CRANKSHAFT/
BALANCE SHAFT
11-2
Mongoose/KXR 250
SERVICE INFORMATION
GENERAL INSTRUCTIONS
• This section covers crankcase separation to service the crankshaft. The engine must be removed
for this operation.
• The following parts must be removed before separating the crankcase.
-Cylinder head (!Chapter 7)
-Cylinder/piston (!Chapter 8)
-Drive and driven pulleys (!Chapter 9)
-A.C. generator (!Chapter 16)
-Starter clutch (!Chapter 18)
-Oil pump (!Chapter 4)
SPECIFICATIONS
Item
Standard (mm)
Service Limit (mm)
Connecting rod big end side clearance
0.05_ 0.4
0.6
Crankshaft
Connecting rod big end radial clearance
0_ 0.008
0.05
Run outæ0.10
TORQUE VALUES
Crankcase bolt 0.8_ 1.2kgf-m
Cam chain tensioner slipper bolt 0.8_ 1.2kgf-m
Cam chain cover bolt 0.8_ 1.2kgf-m
TROUBLESHOOTING
Excessive engine noise
Excessive bearing play
11.CRANKCASE/CRANKSHAFT/
BALANCE SHAFT
11-3
Mongoose/KXR 250
CRANKCASE/CRANKSHAFT/BA
LANCE SHAFT
REMOVAL
Remove the timing chain from right
crankcase.
Remove the left and right crankcase
attaching bolts.
Separate the left and right crankcase halves.
Remove the gasket and dowel pins.
Remove the crankshaft from the left
crankcase.
Timing Chain
Do not damage the crankcase gasket
surface.
°Ø
Bolts
Crankshaft
11.CRANKSCASE/CRANKSHAFT/
BALANCE SHAFT
11-4
Mongoose/KXR 250
Remove balance shaft from the left
crankcase.
Clean off all gasket material from the
crankcase mating surfaces.
Inspect the balance shaft gear teeth.
Burrs/chips/roughness/wear _ Replace.
CRANKSHAFT INSPECTION
Inspect the crankshaft gear teeth.
Burrs/chips/roughness/wear _ Replace.
Measure the connecting rod small end I.D.
Service Limit: 17.06 mm replace if over
Balance Shaft
Avoid damaging the crankcase mating
surfaces.
°Ø
11.CRANKCASE/CRANKSHAFT/
BALANCE SHAFT
11-5
Mongoose/KXR 250
Measure the connecting rod small end free
play (A).
Out of specification (0.8 ~ 1.0 mm) _
Replace the crankshaft.
Measure the crankshaft run out (B).
Service Limit: 0.10mm replace if over
Measure the connecting rod big end side
clearance (C).
Service Limit: 0.05mm replace if over
Measure the crank width (D).
Out of specification (55.15 ~ 55.2 mm) _
Replace the crankshaft.
Turn the crankshaft bearings and check for
excessive play.
Measure the crankshaft bearing play.
Service Limit:
Axial : 0.20mm replace if over
Radial : 0.05mm replace if over
Play
Play
Radial
Axial
ABBCD
11.CRANKSCASE/CRANKSHAFT/
BALANCE SHAFT
11-6
Mongoose/KXR 250
CRANKCASE/BALANCER
INSTALLATION
Install the balance shaft and crankshaft into
the left crankcase.
Install the dowel pins and new gasket.
Install the right crankcase and tighten the
crankcase attach bolts.
Install the timing chain.
Align the mark on the balance shaft with
the mark on the crankshaft.
°Ø
Mark (Balancer)
Mark (Crankshaft)
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