How did you clean the contacts?
Here are my standard instructions for cleaning motorcycle switchgear. Depending on what you have already done, some of it may be useful to you:
The first thing to try is spraying the switch with contact cleaner.
You do have contact cleaner, don't you? Contact cleaner is your friend. It will fix more electrical problems than your buddy who is really into wiring. ;-{)
Note: You need to have real contact cleaner. WD40 is a fine product and has many uses, but it is not real contact cleaner. It leaves a sticky residue that will attract dust and you will have dirty contacts again before you know it.
You can usually clean your switches without taking anything apart. If you look at the bottoms of your switch clusters you will see that there are small holes, just the right size to accept the straw from the contact cleaner and located so that it will spray right onto the contacts.
Just spray the contact cleaner into the hole and work the switch or button vigorously several times, then turn on the key & try it. You might need to repeat the process several times before it works properly.
If you can't get it working after 3 or 4 tries you will need to take it apart.
If you find broken parts you will need to make a trip to the wreckers.
If there is just too much dirt & hardened grease in there for the contact cleaner to wash out you will need to clean it manually. Use an old toothbrush & more contact cleaner.
DO NOT use sandpaper - particles of the grit will become embedded into the contact's surface and cause all kinds of problems.
If a contact is pitted you can dress it with a POINTS FILE. DO NOT use a regular file. POINTS FILES are designed for dressing ignition points and have the their teeth cut at the proper angle &c so that they will leave a very smooth surface.
