My 1990 cbr600 wont charge the batteriy,and wont idol.

New batteries still require a FULL charge. (unless they are not rechargeable)

The control board is probably bad. Did you try a new battery and have you verified that your charger is charging correctly?

have you checked plug gap as this makes any car miss if not correct also coil packs could be faulty

It's in front of your left knee

If the starter turns but doesn't engage then the starter relay is defective. Have it replaced.

It is a good idea to mix 50/50 as the rust inhibitor has a fighting chance then.

haynes manual best bet

Starter could be stuck..
If you are SURE you battery is fully charged with no dead cells..
Try --
(takes 2 peopl) -
Turn the key like you are trying to start it.
At the SAME time - smack the starter with a small hammer not too too hard..
Let me know what happens..

you could have a fault on your regulator/rectifier a chech with a multi meter will tell you. also check generator output.

Check the car battery i suspect that this is fat or has a dead cell you can tell if you have a dead cell by removing the battery tops and looking at the electrolite - acid (water type fluid in the battery) this should be clear if its brown or black your battery is scrap you will need a new battery. some batteries are sealed and cant be opend it may have an indicator on the top of the batteriy this should be green if this indicator is black then again you will need a new one. Also check to see if it is charging a good indication of this is if you switch everything on with the engine running. just rev it up a bit and the headlamps should get brighter that will tel you that the alternator is charging