Does Anybody else's Bike do this?

What's up Guy's, got My 82 750 Out this Year and everything is Fine except it's Running super Rich when I first Start it. And no, it's not the Choke lol. I first Start it, it's Sputtering some blowing a little Black Smoke it's definitely running Rich. But when I get it on the Road and Run through the Gears a few Times everything clears up and it's fine for the rest of the Day.

 

It's not Stock, but I built it 2 Year's ago. So this is the beginning of it's 3rd Season, and it hasn't done this a single Time until now.. But Today marks the second Time it's done it This Season...

 

Pull the plugs and have a look at them. Pull the airbox cover off and see if there's a nest or food stash from some critter.

 

You may also have some fuel getting by the carbs and into the cylinder. Check your oil for gas smell

 

I was also thinking the bowls were slowly overflowing while not in use. Then as you ride,it clears out.

After stopping the bike, let it sit a few hours then start it up again.
If you try 2 hours and it does not happen, try 4 hours, 6, 8 etc. 1 day, 2 days etc.
you can also put a clear tube on the bowls that is long enough to look at bowl height. Check before and after riding.
hook up tight fitting clear tube, screwdriver to open up drain and look at where it settles.
See how I drew a line and as that line gets to center of bowl where the main jet is, its pretty close to 3mm from the top of bowl. If its height is increasing while sitting then your float needle is leaking slowly. even if you have a vacuum petcock, some fuel can still move down from the fuel line into one or more bowls.

 

I did Check the Plug's, but I had been Riding for 2 Hour's without issue so They didn't have much to say. I'll probably have to Stop while it's Acting up and look then.

 

And I don't Think it can be the Bowl's overfilling because I converted it to a Gravity Feed Petcock. So it's turned all the way off while Sitting. But again, I don't "Think" that could be the issue.

 

How about this, My Battery is just about 3 Years old. And it don't Turn over the way it once did. Is it possible that instead of the Carb's Running Rich, the Plug's are Running Cold until the Engine can get a good Charge in the Battery?