[Dr. Strangelove]

Hello everyone, I just got my very first scooter a month ago, a 49cc Chinese Ruckus clone to get to and from work.
Keep in mind I have a very rudimentary knowledge of scooters and how to repair them or identify parts.

Anyways, for the past few weeks the scooter has been stuttering really bad at lower speeds. Once I get past 25 mph it runs fine, but once I slow down (at a stoplight for instance) getting up to speed is, well, pure hell. I've ignored it for a while but it is becoming a problem. It takes me almost 10-15 seconds to get up to normal road speeds (30-40 mph), so when there are cars behind me I hold up traffic and people get pretty angry at me to say the least, honking their horns and such. Usually I just pull over and wait for it to be clear enough for me to get up to speed.

Now I've checked the spark plug and it doesn't look like it is running lean or rich. It doesn't have a white hue or is covered in any excess oil. It looks pretty healthy to me. Tried adding sea foam to the gas tank: no dice.

Some other observations I've made:
-After riding for about 20 minutes, it will clear up and stop stuttering all together, low speed or not. This doesn't help since I'm already at work by the time it clears up.
-It only sputters if I have it on full throttle. If I let off just a bit, it won't stutter, but I can't get up to road speeds if I'm not going full throttle.
-I really can't tell for sure if it runs worse on colder days, but I'm inclined to say it does.
-If I start it up and let it run idle, after about a minute it will shut off. I've also noticed that the motor doesn't sound very consistent. It sounds a bit choppy and chuggy, like it's going up and down very subtly. It's not a solid hum.

Sorry for the long post, that's all I can think of at the moment. I would really appreciate anyone's insight or advice. This thing is becoming a nightmare to drive, but it's my only way to work.