JT Sprockets

Online Catalogue

Yamaha YZ125 U

1988

Front Sprocket

Steel Front Sprocket

Part Number: JTF564

Teeth: 13

Available Sizes: 12, 13, 14, 15

Rear Sprocket

Steel Rear Sprocket

Part Number: JTR853

Teeth: 49

Available Sizes: 38, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52

Aluminium Rear Race Sprocket

Part Number: JTA853

Teeth: 49

Available Sizes: 40, 41, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52

Drive Chain

Pitch: 520

Length: 112

Please note that the chain shown in this listing is for size reference only. For the correct chain type and grade, please refer to the vehicle's manufacturer manual.

Gear Ratio Chart

TeethFront Sprocket
12131415
Rear Sprocket383.17
-16.0%
2.92
-22.4%
2.71
-28.0%
2.53
-32.8%
403.33
-11.6%
3.08
-18.4%
2.86
-24.2%
2.67
-29.3%
413.42
-9.4%
3.15
-16.3%
2.93
-22.3%
2.73
-27.5%
423.50
-7.1%
3.23
-14.3%
3.00
-20.4%
2.80
-25.7%
433.58
-4.9%
3.31
-12.2%
3.07
-18.5%
2.87
-23.9%
443.67
-2.7%
3.38
-10.2%
3.14
-16.6%
2.93
-22.2%
453.75
-0.5%
3.46
-8.2%
3.21
-14.7%
3.00
-20.4%
463.83
+1.7%
3.54
-6.1%
3.29
-12.8%
3.07
-18.6%
473.92
+3.9%
3.62
-4.1%
3.36
-10.9%
3.13
-16.9%
484.00
+6.1%
3.69
-2.0%
3.43
-9.0%
3.20
-15.1%
494.08
+8.3%
3.77
standard
3.50
-7.1%
3.27
-13.3%
504.17
+10.5%
3.85
+2.0%
3.57
-5.2%
3.33
-11.6%
514.25
+12.8%
3.92
+4.1%
3.64
-3.4%
3.40
-9.8%
524.33
+15.0%
4.00
+6.1%
3.71
-1.5%
3.47
-8.0%

Lower gear ratios allow for higher top speeds.

Higher gear ratios increase torque for better acceleration.

Full Gear Ratio Chart (pdf)