Need help!! No 2nd gear!!

[Cota123]

Hey guys, I recently purchased a second hand 2020 Boom Vader 125cc with 10xxmiles. The issue that I am having is that it won’t go into second gear. It will still go into 1, N, 3, and 4 but not second. I pulled the case and the clutch and the actuator and arm roller are clicking it into what should be 2nd but still won’t engage. There were no metal shavings, gears or anything loose in the oil. I’m thinking that it’s just not recognizing it as second and it’s just sitting in neutral. However the display is showing that it is going into 2nd but it’s basically another neutral. Figured I’d ask if anyone has delt with something similar before I pull it completely apart. (Searched forum but couldn’t find anything similar)Any advice helps. Thank you in advance. :thanks:

[Thumper]

It can't get to third without rolling the changer through the 2nd gear position. In the second gear position, the dogs that engage have no choice but to move into position where the dogs go into the adjoining drive gear, so it is likely that the dogs were broken off. They might be large enough to drop into the case and sit there. The only fix might be to replace those two gears, or maybe just one of them (the one with the dogs).

The only way to verify the damage is to crack the case open.

[Cota123]

Not quite sure what you mean by “dogs” but I think I’m understanding what you’re saying. I figured tearing it apart would be my next step but wanted to see if anyone had anything else I should check before hand. I would think if there was a broken gear there would be some sort of metal in the oil but who knows. I’ll crack it open this weekend and update this as I go. Thanks for the reply!

[Thumper]

The dogs look like castle crowns on the gears. They engage adjacent gears to connect the two gears. Here are two good videos to see them, and how the transmission works:

https://www.youtube.com/watch?v=g8xnIFf4id4&t=13s

https://www.youtube.com/watch?v=Xtghypx8mII&t=128s

[Cota123]

These were both super helpful I appreciate the help!! I’ll be pulling it apart this weekend and will provide more info and hopefully pictures if I can figure out how to add them

[Soma]

These were both super helpful I appreciate the help!! I’ll be pulling it apart this weekend and will provide more info and hopefully pictures if I can figure out how to add them


Glad to hear the assistance was helpful! Looking forward to your updates. Feel free to ask if you need any further assistance with adding pictures. Good luck with your project!