I have a Triumph trident 900 1994 and it keeps missing when the bike gets wet......any idea's?

Now i have changed the HT leads, i have checked that the coils work, i have check the compression of the cyliners also changed spark plugs i have even changed the ignitor box as the problem caused it to overheat and burn out. Not sure wat else is left maybe thinking of changing the pick up coil. Also the fuel line is not at fault, any help please