Just bought it, I knew the valves needed adjustment and carb needed cleaning before hand.
Before I cleaned the carb it would run...slightly hard to start cold, easy after warm. It did blow a little blue smoke but went away shortly (assuming the valves were tight).
I cleaned the carb (saw a little trash in the main jet) and put it back together. It ran lots better (still a little blue smoke). My son ran a few laps and then it acted as though it ran out of gas and would not re-start. I took the carb back apart and noticed the float poin had worked it's way out. I carefull put it back in it's place...I can't remember if it had some type of reatiner to hold it in place, I dont see one on the parts diagram but the pin slides to freely in my opinion. Anyways, I carefully put it back together and still nothing.
I changed the plug, checked for clogs in the fuel lines, clean gas prior, went ahead and adjusted the valves (intake was tight as expected) and have good spark but still no start. Engine will turn over fine but I've noticed the starter is naking a little bit of a roar now. The nuetral light is on so no blown fuse. I've got her on the battery tender now waiting on the next step.
I'm not sure what to do from here...what to check next?

 

I was fighting a similar problem for the last week or so. I ended up pulling the gas tank and removing the petcock. Upon draining the tank into a pail I found about 1/4 cup of water and some debris. Once I cleaned the tank and dried it and started fresh, the problems went away.

 

Ah, you have fallen victim to a very common problem with this carb. The Raptor 80 is notorious for this. The root problem is with the fuel. It is such junk these days, especially with the amount of corn based alcohol put in the gas. I recommend you do a couple things.
First. replace the fuel filter regularly. They decompose. For some reason the alcohol makes it soft like a sponge and it will not flow.

Secondly, once again, you probably need to clean the carb out. You might talk to the folks at Raptor80racing.com, they had a replacement carb that is much better...They also have a lot of hop up tips for the stock carb too. They have a problem with slides not opening properly.

Now for the big hints.

Always turn the gas off and run the carb bowl out of gas when you are ready to shut down for the day. Secondly, when you get on for the first time, stand on the pegs and shift your weight back and forth side to side to mix the gas and alcohol again.

These two steps really help with this bike. I had mine taken apart 4 times until we hit upon this. I think the other guy may have had a good answer too. Crud in the tank and possibly plugging the petcock. Take the fuel line off, and blow some compressed air through it back towards the tank and see if that helps.
I assume you have pulled the plug and grounded it to the engine to test that you have spark at the plug.

I sold my son's and bought him a larger machine. I got too frustrated with it.

OBTW, this motor is a cold blooded SOB. I had to run half choke until it was really warmed up to get it to idle from day one. I really like Yamahas, but they missed the boat on this carb deal.