Bike runs better on full tank?

[Pelikan]

I don't think this is my imagination...for some reason I think my bike runs smoother with a full tank of gas.  Could there be any reason for this?

[crzydood17]

it just makes the bike happy!

what are the symptoms when its not full?

possible clogged fuel cap?

[burning1]

Bad petcock? Clogged fuel lines? Clogged breather hose? Biggest difference between full and empty is the fuel pressure.

[XLAR8]

crap in the tank sediment and such... the lower the tank the better the chance of it getting sucked up.

[Twisted]

We are all happier with a full belly aren't we? 

[the mole]

If you have marginal fuel flow due to a blockage in your lines or filter, a full tank will give a little more pressure and help the flow, so it will run better.

[ben2go]

Sounds like a fuel issue.If you have a filter,change it and the fuel lines.

Fuel cap cleaning.
http://gstwins.com/gsboard/index.php?topic=41061.0

Get rid of the vacuum petcock and upgrade.
http://gstwins.com/gsboard/index.php?topic=56352.0