[Jritchie]

last night i started up my xs 650 yand it just kinda chugged along at super low rpm's and would backfire when i was trying to accelerate. when i did accelerate it would hesitate and so i couldnt drive it had to leave it where it was.....any ideas? I've ridden dirtbikes since before my balls dropped but have never had this problem with my first street bike..

 

[jason_hamilton]

If it's got the vacuum-operated fuel taps, check to make sure one of the vacuum lines between the tap and the intake manifold isn't damaged or loose. In addition, those Mikunis don't like to sit for any length of time without the idle jets getting clogged, so fire it up once a week when in storage.
If you're really stuck, Vancouver Yamaha (formerly Atlas) has an XS expert on staff named Gary Guillame ('least they did last time I owned one).

 

[TeeTee]

I take it that you've been riding it all summer and this just started? If so then I also would suspect a vacuum operated petcock line or else one of the rubber boots joining the carbs to the head has suddenly cracked and is leaking air badly. Or it could be something else that is preventing enough gas reaching the carbs or causing an air leak. A bad CV diaphragm is also a possible cause.