Splitting cases on yx140

[The_GDFP]

Looks/sounds like regular Chinese teardown. No worries that I see.

so I got to tinkering with that engine again, as its apart on my bench still and found perhaps a few things...

Firstly the shift drum, on which the shift forks ride, seems to have some weirdness going on.. Whats with the casting? It seems like they just cast it rough enough, with some holes in it, and then machined it down to round. But there is barely any strength left in the thing, barely any material thickness...!? Does that look normal to you??

Secondly inside on of the cases, against the outer wall, there are two cirlcular rub marks. Like a shaft has travelled too far and rubbed on the casing. Again, is that normal. You can see them pretty easy.

Finally, it looks like there is a fine metalic dust throughout the engine, almost like somethings been very finely machined for a period of time. I would not think that its normal, making the oil quite dark with almost a soot like quality to it.

Thoughts?

 

[ash.onmtb]

I guess my major problem is that I still haven't been able to find out what caused second gear to go south...?! Those circled items are the only things that I can find that are out of the ordinary.

Is there anything there that might look wayward??

 

[ash.onmtb]

I guess my major problem is that I still haven't been able to find out what caused second gear to go south...?! Those circled items are the only things that I can find that are out of the ordinary.

Is there anything there that might look wayward??

 

[gazza2003au]

the marble sound your hearing is the clutch dogs slipping here are the gears and clutch dogs i replaced on my yamaha R6 road bike u can see the slots in the gear are worn and the clutch dogs are rounded on the edge the problem with this bike was 2nd gear slipping out and causing a grinding noise if anyone looks this up in a internet search for a yamaha 1999 slipping 2nd gear pictured in the R6 2005 model gears that DO FIT the 1999 model
as for your mates YX engine keep the engine get a new set of gears and tell him to stop grinding the gears change the gears quicker and set the clutch properly and use all of the clutch lever or u will be doing the tear down again