yz125c gearbox

[mainline]

having troubles getting one back together and working

all the right cogs shims in the right order, shift forks in the right grooves on the shafts and selector drum. 

I've got it sitting on the bench and while spinning it over it'll shift up to about 3rd and that's it. Do I pull it apart again or is there some else simple I may have missed?
 
I had forgotten to adjust the selector arm as I'd swapped cases, so that's sorted now

[Nathan S]

Does the shifter move, but not select 4th gear?
Or does it refuse to move the shifter?

My X's gearbox dramas (getting stuck in 2nd, getting stuck in neutral, bad growl sometimes) were:
1. Main shift shaft moving too far to the right;
2. The shift arm being slightly bent in the vertical section (wiggly like a snake).

What this meant, was that it would not engagine the pins on the shift drum properly, and would lightly touch the rivets on the back of the clutch.

[yamaico]

having troubles getting one back together and working

all the right cogs shims in the right order, shift forks in the right grooves on the shafts and selector drum. 

I've got it sitting on the bench and while spinning it over it'll shift up to about 3rd and that's it. Do I pull it apart again or is there some else simple I may have missed?
 
I had forgotten to adjust the selector arm as I'd swapped cases, so that's sorted now

Make sure you rotate the mainshaft and countershaft while you are trying to select gears.

[mainline]

Does the shifter move, but not select 4th gear?
Or does it refuse to move the shifter?

My X's gearbox dramas (getting stuck in 2nd, getting stuck in neutral, bad growl sometimes) were:
1. Main shift shaft moving too far to the right;
2. The shift arm being slightly bent in the vertical section (wiggly like a snake).

What this meant, was that it would not engagine the pins on the shift drum properly, and would lightly touch the rivets on the back of the clutch.

It just won't move, the shift drum won't rotate enough for the shift arm to engage . I've tried a couple of shift arms, both are non-snakelike

having troubles getting one back together and working

all the right cogs shims in the right order, shift forks in the right grooves on the shafts and selector drum. 

I've got it sitting on the bench and while spinning it over it'll shift up to about 3rd and that's it. Do I pull it apart again or is there some else simple I may have missed?
 
I had forgotten to adjust the selector arm as I'd swapped cases, so that's sorted now

Make sure you rotate the mainshaft and countershaft while you are trying to select gears.

yep, doing that, no joy.

Thanks guys, I'm thinking it's coming apart again

[Davey Crocket]

Get a professional to do it......backyard mechanics!!! ....was Brian any help?

[mainline]

Yep, Brian reminded me to adjust the shift arm seeing as i'd changed cases.
I might send it over to 'Back in the Day' and have him fix it for me