So I took apart my carbs to put in new main jets and upon putting everything back together, I cannot get my bike started. I get gas into the float bowl and just recently hooked up the vacuum hose from the frame petcock to the top hook up on the carbs (kick my ass for forgetting this earlier). It will crank. I sprayed starter fluid and it started for a second.

Any ideas what it could be?

Give us a little more info.
Why did you put in new jets?

I put in new jets because I got a new exhaust ( just a fart can) and emgo universal clamp on air filter. I ran it last season with just the new exhaust and it wasn't running right, so I upgraded to 150 main jets with the air filter. Got it running a week ago for a little bit, but now it wont turn over.

Just checked the diaphragms on the carbs to make sure they were lined up and that small o-ring next to them and everything seems okay. Spark plugs look okay also, if that means anything.

Are you sure the choke and throttle are hooked back up correctly?

Yes, they are hooked up. Now I noticed that the small O-ring next to the diaphragm looks like its loose.

Might be stupid of me but I had the exact same problem after working on my carbs recently....did you turn the petcock on the tank back on? I forgot and was  everything but it fired right up after I did this. (My petcock has a slow leak....cmon guys keep it decent....and was allowing enough gas to get through to make the float bowls fill up and fire, then die.)

I'm sure you aren't as forgetful as me, but figured I'd throw out this suggestion.