Tranny Rebuild

[mr hunt]

No idea on the drum tbh, it’s a complex shape to try and check.

If everything measured out right, forks are straight, bearings good, it leaves... drum, gears, and the little spacers between things.

Assuming everything checks out, your plan doesn’t sound unreasonable, I know my second gear functioned a bit wonky and then all the sudden it didn’t work at all and it was rounded dogs. Sounds like maybe the same thing, your 5th worked fine up until a certain wear point and then it stopped working right.

There's also a ****-tonne of play in the drum grooves for the fork lugs to slide through ... in fact I'd go up a level in adjectives and call it slop rather than just play

 

[Rocket Scientist]

This is the problem with trans issues. At times there is almost zero visual differences between one that works fine and one that doesn't. Years ago I made an air shifter for my dad's 900 Kawasaki drag bike. The air cylinder I used was a couple milli seconds to slow. I made about 10 successful runs with it, then one time, it failed to engage 5th gear. After that it didn't want to go into, or stay in 5th gear. Upon year down and investigation, you could barely see any damage to 5th gear. A friend of my father re-cut the dogs and it was fine after that. The long winded point of all this is just the slightest wear /damage to the engagement dogs and the trans goes from working great to not at all.

 

[warp9.9]

Tested for runout and all is good...unless my little bro gave me a dodgy dial gauge ..

Forks are only 13k old (replaced new this time last year) and don't show any signs of wear.

How would one know if one's selector drum was worn? It "looks" ok.

At this stage I'm leaning towards dogs just not engaging properly so will go undercut route and whack it all back together

Did you check the tolerances on the fork to for groove and the drum grooves along with the pin diameter and clearance in the drum grooves? Just thinking out loud. Also wondering about the drum bearings anong with drum concentricity?