RE: starting problems
A few things you could try:
When the engine is cold (hasn't been started within a couple of hours), pull up the choke and don't give it any throttle, then try kicking it. This is straight from my manual, and my bike (01 CR 125) ususally starts 1st kick when I do this.
Drain the gas in the carb before you start it. Lie the bike on its right side until all or most of the fuel spills out of the carb hoses. Make sure the fuel is turned off.
Make sure the air filter is clean.
Make sure the plug is the proper plug for your bike, is in good shape, and is properly gapped. Even a new plug can get fouled badly, but you can use gas or varsol to clean it up.
The floats could definitely be a factor. Did the mechanic just clean the carb or did he check the settings? Carbs are very tricky, but setting the float is actually fairly simple. You need to get the shop manual for your bike to find the proper float height. Floats sit at the bottom of the carb so that when the fuel level in the float bowl rises, so do the floats. At a certain level, a tab attached to the floats will cut off the fuel, letting the accumulated fuel in the float bowl to go down.
My bike is stock but aftermarket pipes may require re-jetting of the carb. You would have to contact either the dealer or the pipe manufacturer to find out. If it's the main jet that needs to be replaced it should be easy to do. Consult the shop manual for specific instructions.
Drain the carbon deposits from your engine. On my bike this is simple, just taking off a bolt and letting some black liquid drain out. Consult the shop manual for it's location.
When you say it runs like a bear, do you mean strong or sluggish? If it's hard to start and runs sluggish, could be improper fuel to oil ratio or air screw misadjusted.
This is by no means complete, but it's a start.