Originally Posted by Pleiades

What ever you do, don't use WD-40 to clean or lubricate ignition barrels. Once the solvent evaporates it leaves a sticky substance which just attracts dirt and further gums up the tumblers; as time passes it eventually turns hard a bit like a tarry glaze. It may feel better at first, but you storing trouble for later.

To clean the lock, use either electrical contact cleaner or brake cleaner in an aerosol, something with a solvent that softens grease and muck and rinses it out but evaporates quickly leaving no residue and is safe on rubber and electrical components. It is best to take the barrel out to flush it through, but it can be done pretty effectively with it in place; it's just more difficult to flush the muck out completely without inverting the lock.

Once it is bone dry (use a hair drier to help) you'll need to use a dry lubricant like graphite powder which can be obtained on the web, or from locksmiths and decent DIY stores. It comes in a bottle with a narrow nozzle and you just 'puff' it into the lock.

If you ever leave your bike outside for long periods of time a good tip is to get a suitably sized rubber or plastic cap to place over the ignition switch. A kitchen sink plug works really well on the Z.