hey guys, so the spark pulg in my buddies ´74 kawasaki 175cc won´t screw in properly, it manages to get about 1/2 maybe 3/4ths the way down the thread and it just stops... is the bikes compression seal reached at either point or must it be screwed all the way down? sorry for the newbie questions but its making us mad and we´re trying to restore a classic. thanks guys