Poxy motor swaps....
The overall height of a long motor is "about" 88.5mm but can vary 0.5mm either way
(even more in very rare instances)
reason is how the actual armature sits on the axle itself, plus how well & centered the armature
sits or shimmed to the magnetic field also how much play there is (and some have considerable play)
(even had piss poor shimming & badly fixed magnets (too high or unevenly glued in)
and though these bit lemony examples are mostly cheapo stock motors, there have been some neodym's with poor QC
The end bells can be nice & near snug sitting in motor plate guides or shit loads of sloppy play
the motor plates sometimes surround the end bell more & sometimes hardly offers much guidance
plus as you wind up the motor height there gets even less side support for end bell
then there is the amount of surround space inside the grip, with very loose support produce a slight clunk as motor starts/stops on examples where the motor/grip has so much play it's like chucking a sausage down an alley
(as the Bishop said to the Actress)
The classic cheapo motor issue where the cheapo motor plate's tiny metal disc falls off throwing out height/adjustment
is another ball ache issue - glue the bastid on the end bell (carefully, not the axle itself but a hairline application just to secure it)
Placement of wires and the way they can alter or throw the motor angle out, really ensure as you push down on motor plate it rises & falls smoothly to ensure hopefully it is all aligned OK still
The tip of the motor, the motor tower....
The above is std cheapo motor - no bearings on the tower, instead of one at the tip
or some have two bearings, one at top & one on the bottom inside with a sleeve
But that isn't the only thing thing....
Some towers have near 10mm diameter and fit rather snug in grip & gearbox entry
Others are near 9mm diameter resulting in more potential play to shift motor angle
and/or allow the angle to shift around when installed
Pinions....
Fucking hell do they vary, some are straight cut at base, some are slightly angled at outer edge
which you have to remember when trying to set basic motor height - it might "look" correct
but the outer edge of pinion's teeth are not quite meshing on outer edge of bevel as you might think
Then there is the angle in which the teeth are cut that you want to ensure meshes as close to 90° as possible
(and hopefully roll smoothly)
Some pinions like G&G's are not straight cut but slightly curved on some of their motors (not all, depends on motor model)
and they can be picky on meshing with certain bevels & stock bevels & stock pinions do not always mesh that great either
I could go on but you get the gist of how shit don't always go to plan....
Try to compare the heights of two motors as a very rough starting point
paying attention to where the pinion is situated, often they are near flush but at times
they can be set a little lower or higher on motor spindle & that is the real reference point to start with
as said check the way the wiring is routed & placed in the grip as you refit the motor making sure the end bell is located correctly on motor plate etc....
If all else fails you might have to swap the pinions, but both are likely to be O type pinions so need motor/pinion puller
and carefully understand how it used to not force the armature further up/down the motor axle
finally, do smear a little - not a ton, of grease on the new motor's pinion
Motor swaps - easy eh - nope
some shit works smoothly but on the poxy wanky M4's especially there is loads of potential issues of slack
plus sloppy motor angles that adds to stuff running like shit - PITFA
for all the sloppy motor suffers out there - this is for your sloppy motor getting on down....
