Transmission getting stiff/locked

[Kdxkid05]

[url]So I put back my cases together and whenever I try shifting. Well it’s a little odd, when I shift up or down it gets super stiff or locked up, and it’s a little difficult to get it unstuck and go into another gear . I could shift all the way up to 6th and then whenever I try shifting down it gets stiff/locked, or sometimes I can’t even get past 3rd gear without getting the same issue, it’s all random whenever it wants to do this i believe .

I can’t post videos here so I’ll link a Reddit post with some videos
https://www.reddit.com/r/Dirtbikes/s/9dHQLUYBX2

[Chuck78]

The engine needs opened up no matter what, bottom line. That may just mean the clutch case housing needs removed, and perhaps you could determine what's worn or incorrectly installed, but there's a chance the cases need split as well.

This is a difficult thing to diagnose over the forum, as it needs a deeper in-person inspection (opened up).

[bufftester]

Absolutely sounds like a reassembly issue. There are a few thrust washers and spacers that are critical to the shift mechanism working correctly. I assume you inspected the shift forks, all the gears and their associated dogs, shift drum...
As Chuck said, going to have to split it to fix it.

[Kdxkid05]

I have taken apart motor multiple times and can’t figure out why I have this issue? It keeps getting stuck between gears and the only way to get it to shift when it’s stuck in between is too bang it into gear with a drill or something. I have got new drum , turret , shift forks, etc. Yet nothing changed, any ideas ?

Reddit post with video

[Chuck78]

Same assembly error 2nd time around if you've had it apart a second time to replace the gearbox parts. Are the shift forks able to be accidentally installed in the wrong position? I can't recall as it's been a while since I've had any cases split (& long overdue on my retired KDX 220).
Bearing not fully pressed in / seated somewhere on the shift drum or gearbox?
Is this in every single gear, or just one or two shifts involving the same actual gears engaging and disengaging?

I would try to simulate the shifts with the cases split if possible (it's tougher to simulate with left-right split single cylinder cases vs top-bottom half horizontally split cases like my Japanese 4-cylinder 4-strokes).

[Kdxkid05]

It does this randomly with gears , sometimes it can shift all the way up to 6th and down with no issues , other times it can get stuck between any gear for a bit, it’s just random and I’ve had people tell me it’s normal for it to shift like this but I am getting mixed responses so idk

[Chuck78]

It does this randomly with gears , sometimes it can shift all the way up to 6th and down with no issues , other times it can get stuck between any gear for a bit, it’s just random and I’ve had people tell me it’s normal for it to shift like this but I am getting mixed responses so idk

If what you're describing happens when you're testing the engine in the shop, on the bench etc not running, this is 100% normal for any shift dog type gearbox. It's not a synchronized transmission like most automobile manual gearboxes, it's a shift dog type, the dogs are square tabs (or flat oval tabs etc) and forked receptacles on opposing gears. When the engine is not running, they may not be lined up. If you're sitting on the bike, simply rocking the bike back and forth to move the wheel (& gearbox driven/output shaft) the slightest bit should allow it to drop into gear.

Examples of shift dogs below, linked from other websites. Examining how they interlock will easily explain how it won't shift into gears intermittently with the engine not running. Is this your issue???

[bufftester]

You mention new shift drum and forks, I assume you measured and inspected them per the service manual for shift grooves and splines? All the circlips and thrust washers installed correctly and in the proper orientation? Same goes for the gears and dogs. As Chuck said, on the bench you have to spin the input shaft while attempting to shift (which it appears you were doing in your video), and it may still be a bit clunky, but it absolutely should not bind up.