Will not start with clutch in and in gear - 1998 Honda GL 1500 SE Gold Wing

motor bike gear boxes rely heavily on a correctly operating clutch
check clutch adjustment
if gears can be selected when the motor is not running , select a gear , activate the clutch and see if the engine will turn over
If not the clutch plates are stuck together so there is where you have to start
if you can select gear when the engine is not running and the clutch is activated then the selector is working
if you cannot select any gear with the clutch running and the clutch is working, indicates a selector shaft or input shaft alignment problem

as per your description problem not clutch since able to start in gear and drive without stall problem sounds more like a fuel delivery not the clutch

MT trans. got it. (said clutch let up.. is the clue)
engine is running right? (sorry)
and you shift to all gears, and car does not move, RIGHT?

if the clutch slips and car will not move in ALL gears.
the clutch is bad, or if a cable clutch, never setting free play on cable is the cause,... done 100s.
or if hydraulic actuated clutch pedal (im too lazy to look)
then if it fails the car can only moved if you start engine in gear.
see?
please post all steps.
i get in car,
i start engine in neutral. (did you) or start in gear with clutch to floor.?
i then select all gears, and release clutch and car will not move.
like that.... and win. (i can diagnose any clutch, ive wrecked many racing, so.... see all horrors) and fixed them by self. all.

if you can only move car , starting engine in gear.?
that is bad clutch cable or actuator (slave or master cylinder)

is the clutch locked all times, or slips all the time.
see? only that need be said.
and 10 other symptoms. (chatters, noises, grabs, etc)

All the Japanese bikes I have owned won't start in gear unless you pull in the clutch lever. There is a small plunger switch fixed to the clutch lever stock (the part that does not move). This switch is connected to the ignition and starter circuits, so when the clutch lever is closed the starter won't turn. Check the bike starts OK when not in gear. If you try to start the bike in gear and it does not start with the clutch lever pulled then the switch is not working. Hope this helps.

Eric, how are you confirming whether or not the car goes into gear if you shift gears without the engine running? One way would be to put it in 1st and see if you can push the car. If you can't, it is in gear.

Another option is to roll the car slightly forward or backward (engine off) while trying to put the car in gear. Once it is in gear, then the car shouldn't move any further. However, if it goes into gear, DO NOT start the car without taking it back out of gear.

The clutch is much more likely to be the problem than the transmission.

If the clutch fluid ever ran dry, then the clutch hydraulics will need to be bled of air. Otherwise, the problem could be the clutch master cylinder, slave cylinder or throwout bearing. Since you didn't report the clutch slipping (e.g. engine revving without accelerating when in gear) it is likely not the clutch disks themselves.

slave cylinder.... clutch fluid doesnt leak from a gear box

The Clutch on some bikes will disengage the starter motor. Yamaha will not allow you to engage gear when the side stand is down. Hope this gives you some idea

The reason why the bike wouldn't start while in gear and the clutch depressed is so it wouldn't start and jump ahead if the clutch was released. This is usually called popping the clutch without in gear without throttle.........Hope this helps.

The sounds like two problems, first is starting an any gear means the neutral safty switch is bad the car should never start unless you have the clutch pedal down, next is the car will not move an any gear, this is due to a bad clutch, its burnt out and so its not connecting with the flywheel, the clutch needs replacing. hope this is helpful.

Clutch discs are stuck, put the bike in gear, not running, pull in the clutch and push the bike back and forth to break the clutches loose. Once they break loose start the engine put the bike in gear, hold the front brake, and slip the clutch a little to remove any built up or stuck crud on the plates.