I have a 2005 Suzuki boulevard C50, it starts just fine in neutral but when I shift into first gear with clutch handle pressed it pulls forward real hard and then dies. Tried adjusting the clutch cable but problem still present. Bike has been sitting for about a year without being road. Road just fine when parked.

Possibly your clutch is worn beyond any usefullness, or is out of adjustment.
Could also be a broken shift linkage.

the clutch is probably either dragging or may just need adjustment

Check the safety switches, specifically the neutral detect and clutch safety.
If the bike thinks it's in gear, or that the clutch isn't pulled in, it won't start!
Check the wiring to the starter relay.

not very likely to be related. sounds more like improper assy. it's pretty tough to tear one up by not shifting right, normally causes transmission problems (broken teeth on gears).

As long as the oil does not have the "energy saving" designation in the rating emblem, synthetic work just fine in the Boulevard.

Check clutch adjustment for proper engaging & de-engagement. If adjustment nut near the clutch lever try adjusting by turning.

It really sounds like something as come adrift in the gearbox or clutch,you should seek advise from your local bike shop..

Backfiring when the throttle is closed shows a lean mixture. Either you, or your mechanic should take a look at the mixture, and there's a 99% chance that that was the cause of your problem :)

Anyway'Lets see turn the ignition key on so you have dash lights etc, Jog the bike back and forth gently while trying to shift the gears, what you are looking for is the green neutral light to come on on the dash.If this does not work..'. turn the ignition off..'. jog the bike GENTLY WITH THE CLUTCH IN AND WHILE THE BIKE IS STILL MOVING A VERY small amount release the clutch.'turn the ignition back on.'Now pull the clutch in and again attempt to shift the gears and activate the green neutral light. If you cant shift down, shift up, if the green lite blinks youve shifted thru neutral go back the other way. When you get a green light pull the clutch in and start the bike. Other Problems.'. You may have an airlock in the clutch line Take it to dealer and have it bled or get a knowledgable person to help you bleed the line. Is your battery OK. Is your kill switch activated.