I got this thing a couple years ago and it's had this problem ever since I've had it. The previous owner stripped off the air box and put on a K&N filter and also put an aftermarket exhaust on it. It starts fine but when you go to move it spits and sputters unless you give it a little choke, then it runs like a raped ape. I thought about finding an air box on Ebay and putting the stock exhaust back on to see if it would remedy this. I went through the carb with a rebuild kit and it didn't make a difference, I also tryed playing with the air screw but I didn't get anywhere. When you pull the plug it's covered in black carbon. Any thoughts?

 

i dont know much about your problem but i believe when you put a k&n and/or pipe you are supposed to rejet it... if the previous owner didnt do this then maybe someone else knows....

 

My first impression was that the previous owner didn't rejet (so it is running lean), based on the fact that the choke improves things. But, if the plug is black, that suggests that it is running rich.

 

replace the plug and rejet ....