Bridge and neck pickups on the Jaguar are the same. If both are adjusted to the same height off the guitar`s body, then the neck pickup will naturally be closer to the strings than the bridge pickup, because of the angle that the strings are at- so the closer (neck) pickup will be louder, obviously. Also, the string vibrates more broadly further up the string from the bridge, and gives the neck pickup more movement to work with, so to speak, making a neck pickup naturally louder, anyway.
If you raise both pickups as close to the strings as they can get without getting in the way, then the neck pickup will probably give you a louder signal than the bridge pickup. If you then lower the neck pickup a little bit, you`ll achieve a good volume balance between the two.
The rhythm circuit on Jaguars and Jazzmasters gives you a separate volume and tone control for the neck pickup, so you can also use that as a way to balance things between pickups, as well.
I`ve been reading on this site about how the Japanese Jaguar pickups are a bit weaker sounding than the original American pickups, and also that they're a bit microphonic, and make squealing noises at high volumes, due to the fact that they aren't wax potted like the originals. Seymore Duncan makes a couple of models of Jaguar replacement pickups, and Fender U.S.A. will sell you their reissue pickups, too, I believe.
