1994-2001 Yamaha YZ125 – Top End Specifications

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Yamaha LogoTop End Specifications For Your 1997-2001 Yamaha YZ125

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General Engine Specifications

Displacement124 cc
Bore x Stroke54 x 54.5mm (2.126 x 2.146 in.)
Compression Ratio
– 1994 – 19959.0 – 10.1:1
– 1996 – 19978.5 – 10.4:1
– 1998 – 19998.9 – 10.9:1
– 2000 – 20018.7 – 10.:1
Lubrication System
System TypeFuel/Oil
Pre-mix Ratio30:1

Engine Service Specifications

New – mm (in.)Service Limit – mm (in.)
Cylinder Head Warpage Limit0.03 90.0012)
Cylinder Bore Inside Diameter
Standard Cylinder54.000 – 54.014 (2.1260 – 2.1266)54.1 (2.130)
Cylinder Mark A54.000 – 54.002 (2.1260 – 2.1261)
Cylinder Mark B54.004 – 54.006 (2.1261 – 2.1262)
Cylinder Mark C54.008 – 54.010 (2.1246 – 2.1247)
Cylinder Mark D54.012 – 54.014 (2.1265 – 2.1266)
Piston Outside Diameter
Standard Piston53.957 – 53.972 (2.1263 – 2.1249)
Piston Mark A53.957 – 53.960 (2.1263 – 2.1244)
Piston Mark B53.961 – 53.964 (2.1244 – 2.1246)
Piston Mark C53.965 – 53.968 (2.1246 – 2.1247)
Piston Mark D53.969 – 53.972 (2.1248 – 2.1249)
Piston Measuring Point From Base of Piston10.00 (0.39in)
Piston-to-Cylinder Clearance0.040 – 0.045 (0.0016 – 0.00180.1 (0.004)
Piston Ring-to-Groove Clearance*0.030 – 0.070 (0.0012 – 0.0028)0.1 (0.004)
Piston Ring Groove Width1.00 (0.040)– (0.051)
Piston Ring End Gap (Installed)
1994 – 19950.50-0.65 (0.020 – 0.026)0.80 (0.031)
1996 – 20010.50-0.70 (0.020 – 0.028)1.2 (0.047)
Piston Pin Outside Diameter
1994 – 199515.995 – 16.000 (0.6297 – 0.6299)15.975 (0.6289)
1996 – 200114.995 – 15.000 (0.5904 – 0.5906)14.975 (0.5896)
Piston Pin BoreNANA
Reed Valve*
Bending Limit0.2 (0.008)
Stopper Height7.4 – 7.8 (0.291 – 0.307)
*2000 – 2001
Piston Ring-to-Groove Clearance0.035 – 0.080 (0.0014 – 0.003)0.1 (0.004)
Reed Valve Stopper Height8.2 – 8.6 (0.323- 0.339)

Engine Top End Torque Specifications

ft.-lbin.-lb.N•n
Water Pump Drain Bolt
– 1994 – 1996788.8
– 1997 – 20018810
Cylinder Base Nuts2128
Cylinder Head Nuts2128
Cylinder Head Hanger Nuts2534
Power Valve
– 1994 – 1995 Operating Rod Screw445
Arm Screw445
– 1996 – 2001 Operating Rod Screw354
Arm Screw354
Intake Manifold Mounting Bolts8810
Spark Plug1520

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