Replace the seals

check and test battery --cdi---connections kill switch and safety switches this is service manual it will assist in troubleshooting problem -------https://www.manualslib.com/manual/1183991/Suzuki-Gsf-400-Bandit.html-

your cdi should be under the tank

its still sucking in air try using a thicker gasket and taking out the "o" ring this may seal the air leak its that or a replacment carb

The clutch got cooked, so it does need to be replaced, unfortunately.

Regards,
matt

hi worth while getting the carbs balanced
cheers jay

No. The gs500 has rotor on right side. 600s have two rotors. The following website will let you compare part numbers. http://www.suzukipartshouse.net/pages/parts/viewbybrand/parts.aspx

The starter motor could be the culprit, check the starter motor.

Real easy, just drain oil, take off side case and remove the bolts.
Take it off as an assembly.
Make sure clutch plates and friction plates are positioned correctly.

Are you sure you need to replace the clutch?
I assume it merely needs a minor adjustment.