125m Trans Binding. Near 3-4th.

[westsideriderz1]

So, i bought a 125m engine on craigslist that hadnt seen oil in ages. after loads of time tearing down the engine and cleaning it, its coming back together. Originally, I had to split the cases because the shift drum was rusted together and i didnt want to force it /bend forks. While in there, I noticed a tooth missing on one gear in the trans, so i replaced it. It was the last cog on the sub shaft closest to the crank, on the magneto side. No visible damage other than a tooth missing.

Now,
I duct taped a drill to the input shaft of the trans on the clutch side, and When i spin the input shaft to the trans, i can shift through the gears,1-4. Occasionally it will bind up inbetween 3-4 and the shift drum becomes very tight. I will have to mildly hit it loose. Its enough to the point i dont believe the shifter has enough umph to bump it one way or the other. Sometimes it will shift all gears normally, sometimes it jams and locks.

My thoughts are that the shift drum may have some play in it if the rust wore it down enough and it could be binding. It could also just be that this engine doesnt have oil in it yet and under running circumstances (both input and output shafts spinning) it wont happen.

What do you guys think?

[westsideriderz1]

https://youtu.be/DA5aSjkAyTc

I posted a YouTube video to show the issue.

Thanks

[westsideriderz1]

So i pulled the shift drum and forks yesterday and put a caliper to them. Everything was in spec according to the book (OD drum, ID fork drum, fork fingers). I also disassembled the cases while the trans was stuck and noticed that it appeared that a gear with dogs was pressed against the gear it was to seat into, and not timed/synched into the gear. In other words, It appears that the two gears didnt sync, but they collided and started moving as one.

[westsideriderz1]

Since no one has responded, I will narrate a bit futher. I believe this may not be a huge issue as loading the output shaft helps the dogs line up. Spinning unloaded (in my case w/o the subtrans on), allows the dogs to press against a gear and lock, rather than slip into its respective slot. I plan to continue with the build.

[barnett468]

.
If it is assembled per the manual with all the shims in the right place and no wear on the shift forks, it should be fine . The input shaft should be rotated counter clockwise and at high speed, not clockwise . If you rotate it slowly, you need to maintain light to moderate pressure on the shift drum and it will eventually fall into gear if everything is good.


PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR