i have a kawasaki zx4 not zx4r, its developed a misfire but only in the wet

anyone have any ideas as to why?

 

Almost certainly a high tension issue. Spray the coils, HT leads and plug caps (no leads and caps it it's stick coils) with WD-40 to get any moisture out of the system. It might make things worse for the first 24 - 48 hours. Spray the LT side as well just to be on the safe side.

A good trick is to lift the tank, run the engine somewhere with poor light, and look for sparks or arcing to make sure that you've got no poor connections or 'past its sell by date' insulation, coils or leads. You won't see much with stick coils unless you're very lucky, but these have a habit of failing. If you can identify the failing cylinder it might be worth getting a coil off e-bay. They go pretty cheap.

Damp can also degrade the ignition performance enough that an 'iffy' plug starts to fail, so check the plugs and especially the electrode gaps.

Rob