Yeti Snow MX kits come factory with 41 tooth upper, 47 tooth lower. We have found on changing upper pulleys to a 39 tooth works well for bikes such as KTM 500/Husqvarna 501 to make gear spacing better for shifting less. On 129FR and especially 137MT with DTS tracks a 39 tooth works drastically better for climbing even with an mx transmission.
For sprocket replacement we recommend using Loctite 660 which can be purchased on our site under loctite in the menu tab.
