I have a ZX9R C1, , clutch is slipping, but has dramatically got

If engine revs increase but road speed does not increase, your clutch is coming to the end of its life and needs to be replaced

If the car heats up trying to generate revs , then it Seems like the clutch plate is slipped.

Sorry old son but your clutch sounds like it has gone to the big junk yard in the sky reserved for dead clutches . When a clutch starts to slip it will continue to do so until that is all it will do . solution a new clutch is required .

Sounds like its time for some new clutches.You can try to adjust it to where you have a lil slack in the lever,which MAY help,but most llikely its clutch plates time.
Good Luck!

If it is going to slip, 5th is where you will notice it first, so it may need new plates, the alloy ones can wear as well as the fibre ones.
Make sure you are using four stroke motorcycle engine oil ( car oils can cause clutch slip due to friction modifiers)

A rough check of the clutch can be done by placing the front wheel against a solid wall, selecting 5, and a handfull of revs, drop the clutch, the engine should stop immediately, if it spins over even a couple of times with the clutch out, it is slipping and needs work.

when was the last time the plugs were changed? start with that , then make sure your carbs are clean.

there is a couple of different ways a clutch can give trouble,one is clutch slip ,this noticable on hills or accelerating from a stop position,you would notice the revs going up and the speed going down rapidly, the other is clutch judder, this caused by a contaminated clutch disc usually from oil etc. from what u are saying it sounds like your car has a slight missfire ,due to a dodgy plug lead or plug , u should remove the plugs and check for track marks where the spark has been jumping to earth and replace that lead.

check for vacuum leaks and vacuum balance carbs

Since you did not say what type of transmission you have i will suspect the clutch is slipping if it's a manual.
If it's an automatic, it could be several things. Low fluid level...clogged filter, fluid needs to be changed..transmission serviced...weak pump, bands/clutch packs worn...etc
Good luck..i hope this helps, please rate me a fixya.