My motorcycle won't start after i took off gas tank?

Its a 95 honda shadow 1100. Cranks but won't start and when i turn the throttle while cranking it. The sound changes but still don't start

Turning the throttle opens and closes the slides or butterfly whether it's getting fuel or not, that's why the sound changes.

Pull the fuel line off, open the petcock and see if fuel is flowing out of the tank.
If it's not, open the cap to see if the vent has gotten clogged, if still not then you will need to remove the petcock and clean it and the filter.

If gas is flowing out of the tank but not filling the carb/s, then debris has clogged the fuel inlet and float needle.

Edit: Oh yeah, if that petcock requires vacuum, make sure the line is hooked up.

Airlock in the fuel lines, maybe? Ya gotta look at stuff, dude.

You probably need to prime the fuel pump

try here for a solution - switching the kill switch with a five second wait between each switch seems to be the answer

http://www.hondashadow.net/forum/72-technical-discussion/104868-need-help-i-replaced-gas-tank-my-vt1100c-cant-get-start.html

ON the fuel bowls there's a drain - crack it and see if there's any fuel in the bowls - Tim D has a good solution but that does not work with later model Shadows. Just keep the battery fully charged (they need a well charged battery to start - it might crank well but not fast enough to start.

Also they are always a biotch to start after pulling the tank sometimes.