Uploading pictures to a 3rd party site and/or a video to YouTube and linking it here would be helpful.  Only you can see what's going on.

I've lost count of how many of those I've done, it's a lot. (If a mistake could be made, I've probably done it!  LOL.) I've never had the issue you're describing so I'm suspecting it might be something like you think it's in neutral but it's between 4th and 5th or something?  Neutral is just a half step between 1st and second and can be found between any 2 gears.  The Yamaha trans is really good about not staying in a "false neutral" unlike say, the old Sachs transmissions which had the "special feature" of a neutral between every gear.  LOL

I don't think you can install the forks incorrectly, but that's a possibility too as all 3 are different.  As is one or more of the little "bushings" that they used on shift drum pins falling out and getting lost.  (I'm happy they changed that design starting on the 1974 175)

And I never saw an answer to my question of how you're confirming you're actually in neutral.  The whole "1/4 turn back and forth" is exactly how the trans can feel when it's simply in gear.

Thanks Mark,

Before I took it apart while in neutral, I marked a spot on the shift drum. Then I use that mark to get it close to neutral, put the trans together and install. Then I look down into the case where the neutral ball should be and the spot for the ball is in line with the hole. 
Bad trans design for reinstalling for a rookie like me. Maybe I just don't have the shift forks lined up properly but I don't see how it would all fit together if not. ??

Tsmitty

P.S. I never completely tore down the trans. Meaning never took the gears apart as they look and measure good.

 

imgur.com/a/Z3U6BFY

Hope this pic posts.

are the sleeves on the shift arms? I'm guessing you saw this.  this is just a cross check

Yep. I got so frustrated that I tore the whole motor apart. Ran everything through the ultrasonic cleaner and now reassembling. All three sleeves are in place and countershaft once again spins freely in neutral. I AM AFRAID TO PUT THE RIGHT SIDE BACK ON!

The only repairs I made was replacing the bearings. They all fit so I wouldn't think that could be the issue.
Ts

Uggh. Got over my fear and put the right side case on same issue. I'm at wits end. HELP!

Works great without the right side. Too bad it won't run that way :-)

going to throw out two brainstorming thoughts:

1. Did you at least partially tighten the drive and clutch axles (ie, pulling the slack out) before testing? I'm guessing yes, but just asking.

2. That front shift arm shaft on piston side...I noted when assembling my own engine there was an "air-pocket" under the sleeve in left half case. I had to lube it well and work the air out to seat it properly otherwise was like compressed air pushing against shift arm, ie right side case. This in theory could have made it difficult to slide on the case. Did the case go on by hand fairly easy? Not sure could be a problem…just things review 

 

Everything seats nicely. Case slides on with light rubber mallet tapping. I have watched several videos and follow instructions to the "T".