I am looking to purchase a programming cable
Does the version you have support programming, and does GM have a program available for that specific version? If not, you won't be able to do this.
If you're not sure, you can ask GM about it at their main Chinese site. If they don't respond (usefully or otherwise), you could try Goldenmotor.ca if they're still around.
so that I can play with the clunk/stuttered start that sometimes happens when pressing the throttle from a stop. I was reading somewhere that this has to do with the hall settings. Does this sound right?
Not the hall "settings" but the hall sensors themselves. If it's a sensored motor and controller, a hall signal or sensor problem means the controller can't tell exactly what position the motor is in, so it can't feed the correct phase current to the correct windings.
Also will ebrake levers be applicable to this motor to improve stopping?
First, if your regular brakes are insufficient to skid your wheels with good tire grip on a surface, I'd vote for improving your brakes first. If you can skid the wheel with them, you can't get any better than that.
The first thing is just replace the pads with KoolStop Salmon, of the right kind designed for your specific type of brake (if you're not sure, KS's website has info on how to choose the right pads). They'll work a lot better, especially if those pads on there now are original, as they've probably hardened up. Then adjust them per the info on SheldonBrown's webpages for your type of brake.
As for applicable, it depends on whether the controller is regen-capable. If it's not, you can open the motor, disconnect hte internal controller, and wire out to an external controller of your choice that has all the features you want.
However, unless you get one with variable regen (like the Phaserunner by ebikes.ca), braking is just on/off at whatever max force the controller is capable of, with no control over it. (some you can choose a level of regen in the setup software or display, but the lever itself doesn't vary this)
Aside from the lack of control it gives you for braking, on/off regen is very hard on the bikes' dropouts and the motor's axle if the regen is sufficient to provide much in the way of stopping power, for almost every motor design out there, because of the very tiny (half your pinky nail or less) surface area that has to transfer all of that torque from motor to frame.
Variable regen means it's just like the way your regular brakes work (except that most regen doesn't go *all* the way to zero and can't hold you there while stopped). Setting this up can be done in multiple ways; thru the brake lever itself, or by engaging with the brake lever and then varying using the throttle, etc. I prefer doing it via the lever since that's already how braking is done, so (assuming you ride bikes generally) the body already knows this and will be doing that in an unthinking emergency stop whether you train yourself to use the throttle for it or not.
make some simple torque arms for my next phase!
Take a look at The Torque Arm Picture Thread for ideas on pinching/clamping dropout plates; much better than a simple torque arm. If you have to go with simple torque arm, make the starting hole slightly smaller than your axle, and very very slowly and carefully hand file the flats out until they so-perfectly-fit your axle flats that you have to tap them onto the axles gently to even get them on, and cannot see any light between the arm flats and the axle flats.
That way you get maximum surface area for torque transfer; normally people have very loosefitting arms and only the very edge of the axle flat where the jagged thread edges are engages the arm at all, which means all that torque goes thru that tiny tiny tiny area. If it doesn't cut thru the arm, it may deform the axle, and allow spinout and destruction of motor wiring or even axle and/or frame.
The stutter only happens when throttling from 0, usually for 5 seconds or so until it catches enough to move forward and stop the stalling. If I pedaling up a couple mph first, it throttles smooth. I plan on pedaling from start as much as possible. Just curious if its proper behaviour.
Does it do the same thing when not under load, with the wheel off ground?
Some controllers / motors are sensorless, and those can have a hard time determining motor position until it is rotating above a certain speed, so they may have the problem regardless of load, though they may also start normally from certain positions and stutter from others.
If it only does it when loaded, it might not have enough power to start you from a stop.
That may be the battery dropping in voltage so much under the load that the controller shuts off the motor to prevent damage to the battery, the voltage rising, controller reengaging, and this cycling until the load goes down enough that it doesn't happen anymore. If the problem is worse the emptier the battery is, that's the likely reason.
It could also be poor connections between motor phases and controller, which are likely to be internal to the motor for this GM MP.
Also it's been sitting for quite some time in the rainy willamette valley. Am I able to repack any bearings in there that are probably rusty and lacking grease?
If a bearing is rusty internally, it's damaged and should be replaced, because rust used to be bearing metal (or race metal).
Replacing is typically not difficult, but sometimes requires heating the covers and freezing the new bearings to get them in without damage to them, since you don't want to apply pressure "across" the races thru the bearings. If you can get them in by pressing *only* on the outer race, you can just do it that way.
If water has intruded it could've built up and corroded hall sensors or phase wires (or even windings), and that could be causing your startup issue.
