Did you happen to check with carb off if idle stop screw raises slide like it should?

Float arms should be parallel to float bowl gasket surface just as float needle closes.

Did you happen to install any aftermarket carb kit parts or check to make sure nobody else has? All Mikuni jets and calibrated parts have the "small square within the corner of a larger square" stamping.

Pictures would be helpful

If I've did this correctly, the link will bring you to a pdf document.

Mikuni Manual

The link failed so here's the url to copy/paste:
VM "Round Slide" Tuning Manual - Mikuni Carburetors
www.mikunipower.com/Manuals/VM_Manual.pdf

On page #2 items 3 & 4 are the most challenging to clean if they become blocked. #3 provides the fuel and #4 the air when the slide is closed. They both provide fuel when the slide is open that is limited by the pilot jet.

Edit: Sorry about the balky link and URL. I found that (using my phone) holding my finger on the url for a couple seconds a menu opens. From there selecting "download" will load the Mikuni manual.

RT - The sleeve was not fitted by a machine shop. They have a ton of different sizes available and tell you what size shaft they fit. Goes on with one careful push to make sure it's not cock-eyed that you can do with the install tool they give you or a section of pipe. I got mine from SKF . 

Thanks for the suggestions to look at the float. I had previously measured it and it was in spec, but barely. Spec is 21 /- 2.5 mm from the sealing flange and I was coming in around 19 mm. I bent the tab that contacts the pin slightly and it was back to nominal. 

I made sure to check that the idle speed screw was doing something my last time in there and it is pushing up the slide. The only change I made this time was taking out the spring that keeps tension on the screw and putting the screw back in fully seated.
Pics here because I can't get the attachments to work.

The only other thing I changed this time was taking out all the jets to check for the Mikuni stamp and size and then reseating them. Everything in there was genuine and had the square-in-square that Mark mentioned, which was surprising to me because they look so new. Sizes were 35 on the pilot and 215 0-6 on the main. 

I gave everything another spray down with carb clean and put it all back together (I'm getting pretty quick at that now) and got an idle!! It was slow at first and wasn't working the first couple times I tried, but I took a lap around the block, let go of the throttle and could finally admire the bike without sitting on it.

Here it is in all her glory: 

Thanks for all the help getting here! I know it's not perfect but definitely a step ahead of where I was.

Nice job!  

I've had to clean a carb several times before it idled right....  the last time I had given up and bought another used one on ebay...  While waiting, I went through it again and it ran fine. (of course after the other one was on the way.)

I used both old-fashioned carb cleaner and ultrasonic.  It was a really old (early 60's) bike that had been sitting for at least a couple decades...  carb looked clean, it just wasn't I guess. 

Congratulations. 

Oh cool, sounds good & positive idle now. Be interested to see how much the idle increases by turning the lights off--magnetic drag or electrical drag etc. Not sure i know what i'm talking about--but!!.

Nice!

So good to hear you're making progress.

Len

+ 1 on getting it to idle Mitch , just for reference  to help others if they have similar issue I pulled apart the top end on my 175 to replace rings and measured slide clearance to bottom and it was little under 1/16”. This is a motor that you could leave idling while going in the house for lunch as they say ….Throttle screw could be turned in one more turn before spring bottoms out at which point slide was about 1/8” off bottom. Imagine that would be wicked high idle 
 And as referenced above that tiny hole drilled at a 45 degree angle into the primary jet opening is about the only source of fuel when running on idle circuit