Originally Posted by mcguyver
Brian, you can tell if your motor is adjustable or not simply by removing the grip and grabbing the rotor assembly of the motor and trying to move it, in and out (or up and down if you prefer). If it moves, it's adjustable. The 490 motor is definately not adjustable, nor is the 460 motor used in Gen 1 guns. How many 480 motors are adjustable (used from Gen 2 in 2004 to 2007 MAX) I don't know. Your gun is likely from the same generational build as mine, so I can check mine as well.
Both my 2007 MAX guns have the bearing, both run quiet, but I don't know yet if it's actually doing anything. The 490 I installed in the M16 2008 MAX-upgrade does not have the bearing, as I left it out.
I looked at both 2007 MAX guns. I received the M4 in March and the CQB-R in April. Both motors are definately adjustable, and have been adjusted at the factory. I have about 25,000 rounds or more through the CQB-R, and maybe 5,000 at most through the M4. The CQB-R is much more quiet that the M4, by alot. The motor shaft on the CQB-R shows signs of some wear from where the bearing is pushing on it, where the M4 shows very slight wear, barely noticeable.
The M4 is about as loud at the M16 with the 490, but both of these gun are virtually new, with no motor brush wear. The CQB-R has about 1 mm or so of brush length worn down, and afetr a year of play there was brush residue left in the grip, on the endplate and the rotor. Both 480 motors moved about 1 mm or so in total.
Perhaps as time goes on, the gun will get more quiet. To me, it sounds the the increased whine is coming not from the motor, but from the gearbox. I will used my M4 lower more this year and see what happens. If the extra whine does come from a slight rubbing of the sun gear with the gearbox shell or with the bearing plate, as time goes on it will wear a small track in the gearbox shell and this will decrease rolling resistance of the sun gear and should reduce the whine. As the sun gear is harder than the gearbox shell, this should not pose a problem of gear wear. The pics I've seen of other guns where this has happened have only showed the surface finish removed for the most part.