I have a 2000 Savage LS650, I just got it for Christmas. It's my first bike and I love it. The first 3 weeks I put over 1100 miles on it, bringing it to 14,000 on the bike. It has a Raptor petcock (1st change, thanks for the tip, did this day 1.)I was only getting at BEST 31mpg. Then it started idling slow at stoplights, and died. Over about 3 days (& 30 miles) it got worse idling slower, it needed about 1/8th of a turn on the throttle just to idle. Then it turned off at a stop and wouldn't restart. I came back 2 hours later to pickup the bike and it was sitting in a POOL of gas, over half my gas tank. Got it home, gas was FLOODED in the air box (over 12 ounces!!) So I figured I had a stuck float or a ruptured seal in the carb. Pulled the carb, it was gunky but nothing terrible. The float was still springy, floats, and has no fluid inside. Cleaned everything in carb cleaner. Main jet was 150, pilot was 50, I don't remember the top 2 honestly. Put the carb back on. Now it seemed like it wasn't getting spark. Replaced the spark plug, it was BLACK due to the rich fuel mix (I'm guessing I need a smaller main and pilot jet although both match what I've read on here). Replaced the oil, there was a ton of gas in the oil I emptied. Then it started right up, but was idling a bit rough. Tried to adjust the idle/air screw, and I can turn it all the way in WITHOUT killing the engine (so I assume I need a smaller pilot jet, ok), found the "best" crappy idle about 1/2 turn out. Bike ran, then turned off due to low gas. Went to reserve fuel, I've done this 6x and always got 15+miles, but I ran out of gas on a 4 mile test ride. It was DRINKING fuel, and running sluggish, responsiveness on the throttle took 2-3 seconds, but at high idle (4000+?) it ran ok. Then I got gas, restarted it, ran at 1/2 throttle for a minute, let off and it died. Tried to restart 6 times before the battery died. Got a jump, while connected to another vehicle the bike idled perfectly like the day I got it. Then disconnected the cables and it died. Replaced the battery, and then the starter solenoid was not working (checked the starter with a jumper cable and it worked). Took off the tank and just touched the solenoid and it worked again, rewrapped all of the wiring. Then the petcock was leaking (I guess I bumped it when I set the tank on the ground), so I replaced the petcock. Now we're current. I tried starting the bike today, and now it will not start, and every time I try to start it I get gas out of my EXHAUST PIPE!! I am now at a loss. I'm going to pull the float bowl off the carb and put in a 145 main and 45 pilot when they arrive. But I don't think that's my biggest issue, just part of my crappy gas mileage. What is happening with my bike?! I need my happiness back.

JOG is right, something to do with the float valve.
Jets are about right.
Take the float valve out, there's a screen at the inlet. Clean it out.
Check the tip, is it indented? replace it.
Check the float level, either by measuring or with the clear tube.
And turn the petcock to off when not riding.

When you get the carb back on the bench, inspect the tip of the float valve. The rubber tip should be pliable and without any indentation or distortion. There is also a rubber o-ring under the valve seat that should be replaced as well. Finally, get a q-tip and some metal polish, and polish the seat until it shines.

Like I said above, polish the seat and replace the o-ring. If the seat has contamination, the rubber portion of the valve wont sit all the way down. If the o-ring is hard, it can't do its job.

I attached a photo from a CB900 carb book so you can see what I am talking about.

I replaced the needle seat about a week ago with all of the other jets and internal pieces. Everything internal is new, and genuine Mikuni parts. I was getting at best 30mpg prior to my bike flooding everywhere. I rebuilt the carb. Now the bike will start on the 3rd or 4th try, but is sputtering and will die quickly, as well as sputtering gas from the exhaust pipe (every time it tries to start it is spewing gas from the exhaust) and putting gas mist into the air box. This seems to be a continuing issue. I just put in a 47.5 pilot instead of the 52.5 that was in there originally, I will try it out today but I doubt the pilot changing 2 sizes would cause the level of flooding that I am seeing. I likely will need to do another oil change this week as I'm pretty sure there is gas in the oil again. Everything "looks" right, I'm not sure what I am missing.  :'(

The gas tank is less than 6 months old, and was flushed about a month ago when I installed the Raptor.

Attach the clear tube running along the side of the carburetor using plastic ties. leave it there so you can observe fuel level while the engine is running and is spitting gas out the exhaust and intake. Does the fuel level go above the bowl gasket? After setting awhile with the petcock on, does the fuel level rise? To rule out float valve, you need to verify the problems continue, yet carburetor fuel level never goes higher than it should.
You are correct, slight changes in jet sizes is not going to fix this.
You may have two separate problems, like a float valve that some times sticks and a hole in the side diaphragm or valve timing/adjustment.

You do have the fuel line connected to the correct input, right?
Labeled "fuel tank line" here

Where can I get replacement jets for this carb Serowbot? After nearly 3 weeks, taking the carb apart like 8x, and the bike still not working, I have come to the conclusion that although all of the internals look to be OEM Mikuni parts, maybe something is flawed. No matter how I adjust the idle\air screw it runs like crap IF it will start at all. Every time I adjust the float the level looks good, about 1/16"-1/8" below the float bowl seal. I adjusted it to give nearly 1/3" below the float bowl seal and the bike still seems like it is flooding. The bike has a 147.5 main and a 47.5 pilot.

I've only had the bike since Christmas, but I put in almost 1000 miles in the first few weeks, EVERY tank only got 30mpg max though! And then one day it just sputtered out at a red light and then dumped all the fuel into the air box. Cleaned the carb. Still nothing. Ordered a set of Mikuni jets from ebay, it ran for about 5 miles and then choked out. I have now tried it with the original jets, and replacements and both sets or combinations of both sets all produces the same SUPER rich conditions that will foul a spark plug in less than 5 minutes. If/when it starts, it will run with over 1/4 throttle, but then even at higher RPM it will start to choke out after a moment or 2 of holding the engine speed. The exhaust is straight black. Nothing I do seems to change anything.

And yet my bike will still black out a spark plug to the point it needs to be pulled and cleaned/replaced in less than 5 minutes of choppy idling and running.  

I just want to order all new everything inside the carb, but can't find what I need anywhere. Can anybody provide a link and part numbers for like everything that can be replaced inside the carb?

I am so frustrated and just want to be on 2 wheels again! :'(