I got my first bike ('06 S40) a few months ago, and I've been lurking here ever since.  I have a problem I need to ask about.  I've got a fuel starvation symptom at all speeds, even idle.  It begins right away after the bike is started.  The bike can be ridden, but sometimes it dies, sometimes it doesn't.  But while riding it's like it is not getting enough fuel...through all the gears.  I've checked the fuel line, cleaned the air filter, and done the petcock test.  Those didn't help.  I thought for sure it would be a petcock issue after reading about all the trouble here.  
I'm an extreme newb mechanically but hoping to change that with this bike.  I need advice where to look next.  Thanks.

WeWontBlink wrote on 09/14/12 at 08:22:23:

They run lean stock,I would try some Sea Foam in the gas to clean and lube the carb.

verslagen1 wrote on 09/14/12 at 08:55:14:

Thanks for the input.  I wil definately try these things when i get off work.

I doubt this is your issue, but I will share my experience just for giggles.  I was new to a bike (recently) and thought I had enough fuel in the tank to make some test rides, and purposely left it nearly empty because I knew I would have to drain and pull the tank as soon as I got back to the garage.  

Anyway, I had several episodes on test rides with the bike spitting and sputtering and (from experimenting) had to turn it to reserve to make it home. I thought it was a bad carb setting or an issue with the vacuum line on the carb/petcock because that is what I was tinkering with and testing.

Come to find out, the tank just didn't have enough gas in it to operate off reserve...hence, it was doing exactly as designed.  

Lesson learned is that what I think is enough fuel to be beyond reserve isn't the same as what the bike thinks, and if I don't want to walk, I'll go by the bike's rules.

I once had an issue, nearly the same. First the bike won't go beyond abt. 50 mph and then sputtered heavily. Then the speed decreased more and more I could go. At last, I could hardly act the throttle any little bit without bangs and sputter. I knew something must be in the carb bowl going on.

When I looked there to see what it is, I found a birch tree seed which had settled in the main jet. It must have got in through the venting tubes, which were correctly placed in the square frame liner.

I also know, small condense water parts, separated and stirred up by vibrations, may settle in the jets and can't get through because of their surface tension. I had this issue several times on another bike.
Then just drained the carb bowls after tapping the carbs with a screwdriver handle and I could go on again.

yeah, 1's a inny and the other is an outty.  I don't how the others are cleaning it, perhaps spray it with carb cleaner.

We,

If you try the other stuff mentioned above, and still no joy, try swapping the spark plug for a new one......

IHTH!

Put a hose on the bottom of the carb drain spigot and run it into to a container.  Then set the petcock to PRI and see if you get a steady fuel flow into the container.  This will test the flow out of the tank, through the petcock filters, the fuel hose and the needle and seat of the carb and into the float bowl.  You should get a steady trickle.  I will time it on my bike and let you know how long it takes to drain 16 oz....that will give you an idea if your flow is normal.