Lifan ares 125 gearbox, transmission

[pleho_mms]

Hi, i bought lifan 125 pitbike without stator plate. Previous owner broke it but he purchased bike new and rode it for 10 days. After replacing stator and crankshaft bike started to jerk in 3rd gear. Yesterday i removed transmission and everything was fine there was no damage. What could cause that and how do I fix that, transmission was good before crankshaft change. Please help!

Sorry for my bad english!

 

[zwebx]

how was the spark and the crank bearings?

 

[pleho_mms]

everything is fine just 3rd gear crank bearings are new, but in 3rd gear sporckets don't aling.