+1 ... That's where I'd be looking first.

 

OK... I changed the petcock valve (it was a mess), and was also informed by my local know-it-all motorcycle guy that there may have been an obstruction in the cross over flow tube going from the right hand section of the tank to the left (it crosses in front of the tank down low). So I replaced that tube as well. So far, it's running, but I haven't been able to go out and put another 110 miles on the bike... it's raining, and dark, and I'm a *****! So I think it should be much better. By the way, I didn't use a Pingle valve, but used another type that has much better flow and was about 1/4 of the price. So for about $35.00, I think I got it all worked out. Thanks again for everyone's input. Ray

 

You probably have contaminated carb too. You should have dropped the float bowl on the carb to make sure you don't have crud in there too.

 

Hope your el-cheapo gas valve works out for you. I saved a buck on one of those Arlen Ness valves and after about a year, it got to where it wouldn't switch off and on. Ended up going with a Golen that the local indie had in stock, the Pingles he had faced the wrong direction and I was far from home. If you start noticing it getting sticky, replace it as soon as possible.
You aren't by chance running an in line fuel filter are you?

 

I was going to buy the Pingle valve, but the guy at the shop swore by this one he sold me. I think the gas today (with the ethanol) plays havoc with all of the gas related pieces, no matter what you do to help offset it. The valve I took out was also hard to turn, but the screen was filthy and I think that was the real problem. As I mentioned, the bike runs great normally. It was when I got down to a certain level that it would crap out, and after seeing the screen filter and how gummed up it was, I have no doubt that was the cause of no gas flow. So we'll see what happens with what I replaced... and hope for the best.

 

You probably solved your problem, but could have done the same thing by just cleaning the screen. I hope you saved the stock petcock since it'll probably be just fine after a good cleaning.

Had a couple of friends that had a similar problem. Bikes ran fine on the first half tank of gas, but would hardly run at all when the gas got low. Their problem was that they both had installed filters in the fuel lines, but hadn't shortened the line. The extra length of the filter caused the fuel line to kink slightly. The weight of a full tank would force gas past the kink, but when the volume got light enough the kink would starve the carb. I fixed the same problem for both of 'em......they were brothers..........

 

If you find yourself removing the tank again take the opportunity to install a quick disconnect on the cross over line. Colder makes a very nice quality quick connect. The addition of the quick connect makes removing the tank in the future sooooooooooo much easier.

Just a suggestion.