My '03 SERK did this for over a year with me and the local indie trying to solve it. Never threw a code either. I went through the same process of elimination: fuel filter, bad gas?, crank sensor, check connections, etc. Then, I read about another rider on another forum with the same problem and he finally solved it by replacing the throttle position sensor (TPS). So, I thought I'd try it since the part is only about $30.00 and very easy to replace. Problem solved; I was a happy rider again. I certainly thought a bad TPS would throw codes, but mine did this intermittently for over a year and never did. Go figure.