it depends onn the gas, Reports posted here say that ethanol blends can go bad as quickly as three months.

Was it bad fuel ?
My s-40 run better w/ the choke out even w/ bran new fuel in it, till I did the white spacer mod. It runs like a different bike now.
I myself have never had a problem w/ 1 yr old gas.

Read this:

http://wiki.answers.com/Q/Can_you_mix_old_gasoline_with_new_gasoline

Hell no, I've used year old fuel myself in lawn mowers, and have seen illegal Mexican aliens use old waste gas in their everyday beaters.  But I would never run it through anything good because I'm the one who would have to take everything apart to clean the mess, if I was unlucky.

According to what research on the 'net says, the gas will lose it's octane rating significantly starting in about 3 months.  Also, around that time it can absorb moisture.  Being involved in the Haz Waste industry, I used to arrange to have months old gas removed from various above ground tanks that had collected it from old junk cars and equipment.  From there it was supposed to go to an off loading site to be disposed of in accordance with State and Federal regs, but before it did a lot of it illegally ended up in employee's gas tanks.  It would be strained with a t-shirt as it was poured into the car's tank, and the t-shirt would collect fine brown silt.  The cars seem to run okay but for sure the octane rating was not what it used to be, and I bet the additive packages had changed from age.

The point is that if you have old gas in your bike, why not drain it and use new product?  Why be so cheap, especially when there is no question that the octane rating lowers with age? Is it worth the gamble, just to save a few dollars?