2003 honda 750 ace, with the clutch lever pulled back when you put it in gear the engine dies.

swap fuel filter first but the in gear issue could be a clutch adjustment needed...

Usually motorcycle-grade 10w30 or 10w40 works well. NEVER use automotive oil in your bike. It was fine to do back in the 80's, but not now. Automotive oils have too many additives in them and eventually cause clutch slippage in motorcycles. Cars don't have oil-dampened clutches in their engines. So they can use slipperier additives.

check clutch free play if to much there take some up but leave a little so there is some free play or the clutch will slip

I have the 2003 Honda Shadow 750 ACE and had a problem with the bike intermittently not wanting to start. All is good but when I hit the start button nothing would happen. Took it to the dealer and was about to pay them about $75 just to diagnose it when of the customers told me that the 2002-2003 Shadow line had came with a "sticky" clutch safety switch & starter button. First thing put the bike in neutral. If it starts, check that the (2)wires coming from the clutch lever are fully inserted(just push on them). If it still wont cut on, push the start button and "wiggle it" while pushed in. My problem came out to be the at the clutch safety switch. I removed the lever, pushed in the switch so that it popped out and sprayed the tiny hole on the side of the plastic switch with electric parts cleaner($3.00 @ the auto parts store for a 12oz. can). My bike hasn't had a problem since!

Your kickstand switch is either broken or out of position. The bike kills the engine as a safety feature if it thinks the sidestand is down and the bike is put in gear while the engine is running.