is the lead meant to be joint to the spark plug cover, or should it be able to be pulled from out of the cover? One of the leads comes out quite easily and seems quite corroded at the join. I don’t particularly won’t to try pulling on the other leads to test if this is normal in case i pull any out.
if ht/copper lead then yes they can be just pulled out, if corroded just cut end bit off and reattach, screw it on though, pointed connector bit on plug cap goes in the middle of the lead.