Yamaha TZ125M1 Owner's Service Manual page 252

Driven sprocket
Drive sprocket
16T
17T
18T
EC71P011
Selection of the secondary reduction ratio
(Sprocket)
Secondary
w
reduction =
ratio
35T 36T
2.188 2.250
2.059 2.118
1.944 2.000
The larger value, the higher speed ratio
The smaller value, the lower speed ratio
EC72N000
Drive and driven sprockets setting parts
Drive sprocket 1 1
Driven sprocket 2 2
* Factory installed
7-18
SETTING
Number of driven sprocket teeth
Number of drive sprocket teeth
Factory-set secondary
reduction ratio
37T 38T
2.313 2.375
2.177 2.235
2.056 2.111
Part name Size
16T
* 17T
18T
35T
* 36T
37T
38T
39T
TUN
36/17 (2.118)
39T
2.438
2.294
2.167
Part number
938AA-16198
938AA-17196
938AA-18199
4JT-25435-20
4JT-25436-20
4JT-25437-20
4JT-25438-20
4JT-25439-20