Where do fuel lines connect to on 92 zzr 250

the best oil is the oil recommended for the bike
any other oil may cause problems in the clutch and gear box
shock absorbers are just that and are pistons with small holes and flap valves that restrict the flow of oil through the holes on rebound
there are springs in the forks as well and the seals just stop the oil from coming out the slides
pulling down tight for transport should have no affect

petrol is low swtch to reserve or clean your fuel **** they have filters on them may be block this happens from time to time
and check you have a good spark

most likely a fuel overflow hose and it is simply a vent (does not connect to anyhtign)

The fuel mixture is probably running too lean. Old, hardened rubber seals between the carb and the cylinder are letting un-carbureted air into the fuel/air mix.

Two tanks.

sounds like you blew a set of piston rings. instead of building compression in the cylinder its pressurizing your crank case forceing the oil out the breather into your air box

Please check for a grounded wire, which cause your erratic sparkplug performance and headlight operation

dirty or loose grounds or a dirty or malfunctioning relay check your harness connectors as well get some electrical grade spray and pop open all connectors and give em a good dose undo all grounds and clean and re tighten them cheapest and easiest is sometimes the best Bought a bike dirt cheap cuz two mechanics couldn't figure out that the coil pack under the tank was crusty and from oxidation