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Yamaha mt-125a 2017 transmission shifter issue

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My mt was recently dropped and was stuck in first gear I've opened the transmission and found that the aluminium that holds the metal dowel pin in place has broken (photo and video attached) is there anyway I'd be able to get this welded if not I'd have to replace the casing but it looks like I'd have to replace the whole bottom half of the engine which is a lot of work for a dowel pin 🤣 anyone have any ideas...






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Hi jack,

The casing is cast aluminium, if you're not familiar, they make a mold and pour in molten aluminium and it sets into the shape they designed, it's quite strong, but if it gets damaged it's a different story.

In my experience aluminium welding is not that successful especially if its going to support something, it's more suitable to say,.. repairing the outer casing... to seal up a crack. (which doesn't always last). Regretfully you're looking at replacing the damaged casing with another or a new one.

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Hi Jack,

If you have seen my thread - you'll see a similar issue with my YBR -and found almost exactly the same issue inside when I opened it up. I didn't drop mine, but highly suspect that's what has happened to it in the past. Don't worry about the gear and coil spring on the very left of the picture, my bike has a kickstarter.


Mine was welded - poorly. As a result I had to shim with some extra metal (which so far is holding up). This pin needs to be *solid* and not move at all. Mine had a really small amount of play, but would still prevent me changing gear properly. The pin allows the shift shaft to return to it's central position after each shift.

My next option was to have the pin welded in place - and the final option to replace the actual crank case.

I would also check that your shift shaft is not bent out of shape, and that the gears all work as intended by shifting it manually by turning the shift drum - this is easier when the spring is taken off that holds the stopper arm.

I can't see it properly from your video, but it looks like one arm of your shift shaft is actually broken (that grabs hold of the little pokey bits on the shift drum star). Definitely check around your engine for any broken bits and (although you most likely have already) drain all the oil and replace with fresh once you button everything back up. 


Edited by sparxooo
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