Had the same problem with my 500. I ended up parting it out and going with a 400. Glad I did.

 

On this carb the manual shows the float level is adjusted when the carb is held sideways,float arm tab barely touching the needle. Usually sets at 13mm (.051) from carb base to bottom of float, BUT if it was set correctly,when held upside down the bottom of the float usually will be parallel with the carb body.

 

It is adjusted right on the money...new float assembly? The o ring slides pretty easily out of the seat for the float. No o ring for it came with the rebuild kit and I can't find one that fits.

 

This is a special metric o-ring.. Try a good hardware store like Ace,etc to see if they can help. If the float arm and float pin are wobbly,could be source of the problems. Most people over look this because they don't come in carb kits. Must be ordered from a dealer or cheaper online. If you do need these two items just order the new o-ring with them.
Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

Opt, I'm getting frustrated. I'm not sure what's going on with my wheeler. I did all the above, and still spitting when given throttle. It idles fine, but as soon as I touch that throttle it shoots smoke out of the air box. Could just a one thousandth off of my valves make this happen?

 

We've been talking about the cam,valves,etc,but one thing you can try is unplugging the black wire from the reverse limiter module and see if this solves the problem on spitting back. They can short out and cause limiting in forward range.Item #30 Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse