Kx125 transmission help

[djblock]

Hey everyone, got a knocking noise from my transmission
in 3rd gear. Every other gear does not make this noise.
Took the chain off and applied a load on the sprocket while idling, every gear was fine but 3rd. When I applied pressure to it a knocking sound was made. I thought it was the main
bearings but only being one gear maybe metal chip jammed in
3rd gear teeth. Any help Thanks

 

[nickyd]

what's it sound like? a clunk in and out of gear? does the bike "skip" when it happens? if so, 3rd gear is worn. the dogs on the side of the trans wear and can cause the skipping