Good day fellow tone seekers! So this one came in over the forum and I promised I'd get to answering it in blog form ... so here goes! Possibly no other pickups are as responsive to height adjustments as Jazzmaster pickups, but also possibly no other set so strongly begs you to break the rules, so seriously, folks ... take this as no more than a STARTING point!
First remember the hard-n-fast rules:
As you move the pickup closer to the strings, the tone gets brighter, more focused, more sterile, and ... louder.
As you move the pickup further from the strings, the tone gets warmer, more rich and organic, more complex in overtones, and ... quieter!
Soooo ... Adjust away given these rules to achieve the tone you are looking for. Here you may run into a road-block of sorts; the vintage Jazzmaster pickups were not calibrated to bridge and neck positions the way I make MY sets, ans as such, the bridge always sounds wimpy and too bright and the neck sounds overpowering and too dark. You see the roadblock, right? To make the bridge pu LOUDER, you move it as close as possible to the strings, but that only makes it even more bright ... ugg! Same goes for the neck, to make it less overpowering you move it back, but then it gets even darker still. And so ya got to just do the best you can, and if that doesn't get ya there, you may need to look into buying a new set of pickups that are PROPERLY calibrated to the respective positions.
Having said all this, here are the measurements on MY personal 1965 Jazzmaster, and on these big, flat pickups, a set of feeler gauges will be your best tool! Measurements are taken un-fretted:
Bridge: Lo E: 0.15" / 3.9mm Hi E: 1.46" / 3.5mm
Neck: Lo E: 0.14" / 3.5mm Hi E: 0.11" / 2.7mm
Yep, those are CLOSE, but ya gota to remember two things here: first, they are vintage wound pickups, fairly low output, and second, I LIKE my Jazzmaster to be "surf guitar" bright! So friends, there ya have my advice as best I can give it, now go forth and tweak away!