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The main contactor is just for the high current feed to the motor controller. There are several high voltage feeds that leave the battery by alternate routes for the DC-DC converter and MBB just off the top of my head.

As for the 12V battery on the Gen3 bikes, that was likely just to make their lives easier. The last rendition of the Gen2 stuff included a smaller always powered 12-volt module in addition to the main DC-DC converter, probably to address the OBD port requirements of a constant 12-volt source in Europe.

That is relevant. Thanks. Do you recall if the contactor was closed?

This is just a short in the dark, but I'm wondering if anyone here has intimate knowledge of how the Zero BMS detects battery isolation from the chassis. I'm familiar with how the theory of it work, but I don't know what resistive values Zero uses in their BMS and whether they actually execute the checks against the full battery voltage or some subset of it.

The reason for my inquiry is that I have had an analog pressure sensor on my rear brake hydraulic line for about the past 2 years. Several weeks ago, it started randomly activating on its own. This degenerated into activating near constantly and rhythmically. Upon investigation, I found that the issue was a floating voltage relative to battery ground present on the frame. This degenerated to the point that I can now measure exactly 1/2 battery voltage between the frame and battery negative keyed off. Upon keying on, the voltage between frame and battery negative becomes a square wave from 0 to 1/2 battery voltage on about 2/3 second cycle, strong suggesting something under a microprocessor control. Given how chassis isolation is measured, I suspect this circuit to be the culprit, but I cannot be 100% certain.

I am at least certain the issue lies within the BMS or its wiring because I have removed the front cover from the monolith and disconnected the ribbon cable at which point the floating voltage on the frame disappears. Obviously, I cannot power the bike at that point since the BMS has no power.

The motor is NOT adjustable. The mounting surface on the left side is machined onto the frame such that the motor is as much as it can be guaranteed, to be true to the mounting axis of the swingarm, which in turn as much as can, guarantees that a user can then align the wheel sprocket using its adjusters. The position of the belt on the sprocket is probably a red herring. But by all means, keep wasting your time trying to strain the motor against its mounts. At worst, you'll prematurely destroy your $1k-2k motor, assuming you can get a replacement at all since this wouldn't be covered under warranty.

First thing I would do is completely slacken the mounts on the right side and back off the adjusters so that the motor is held only by the left mounts, which should be more accurately machined relative to the swingarm that you'd be able to measure. Then, mess with the wheel alignment and see if you can get better results with the belt noise -- NOTE, don't heavily load the motor with the right side unsupported. I can pretty much guarantee the motor doesn't have the torque available to tear itself off the left mount, but the added movement from lack of support on the right side wouldn't do it any favors. Also, for this test, the belt tension would have to be set very low. You can try to set it to the bottom of spec, but you'd want to put some kind of feeler against the right side of the motor to make sure that as you tensioned the belt, the motor wasn't twisting. If the motor starts to move, stop applying tension and just try to get the alignment right.

If that fixes the alignment, that tells you that someone messed with the right-side mounting bolts and racked the motor. If, however, you still can't get the alignment better and feel you need to rotate the motor, you can adjust it ONLY by adding shims under the bolts on the left side. Again, the adjustment of the mounts on the right side are there solely to facilitate mounting the motor from the sides without stressing it or the frame when doing so.

And just to make sure this is clear (even though I've said it several times now), "better alignment" does not mean the belt is riding in the middle or even off the flange. You consistently describe the belt as riding up the flange, even if you don't understand that definition. When the alignment is correct, the belt might very well still ride against the flange, but you should not see any part of the belt being lifted by it as it engages. Don't let its position on either of the sprockets be some kind of red herring to you.

I'm not sure you understand ... by your description that the belt is lifted by the flange -- even a small amount -- and then falls back down as it rotates around, that is called riding up the flange, and no timing belt should do that. No one is suggesting the belt is riding up on top of the flange. In a fixed center design, that isn't even possible unless those centers were reallllly far apart, the belt was extremely elastic, or there was grossly insufficient tension, none of which apply to these bikes.

And the image does not suggest the belt needs to move a mm to the right. I don't know where people get this idea the belt needs to be centered on either pulley, but it does not. I know Zero says something about 1 mm off the inner flange of the rear wheel. As someone who has to write instructions for equipment I design, I can tell you that number came out of someone's @ss because an instruction needed to be written and some number was needed to give people a target -- and flush against the flange is a poor instruction for reasons that are beyond this post, but you can likely figure it out. The position on the sprocket is irrelevant. The only way that number would be relevant would be if Zero did such a good job of aligning the motor and its sprocket in the frame relative to the rear wheel that 1mm off the rear flange coincided with the point of proper alignment. It's possible, but given some of the recalls I've seen, I doubt they went through that much trouble. The belt just needs to run true between the sprockets. If your belt is being lifted at all by that outer flange then yes, the alignment needs to be adjusted, but when properly adjusted, the belt might very well still track against that outer flange.

It's unfortunate your bike has always made this noise. Was it new when you got it?

When the noise was at its worst turning the wheel slowly by hand I could see that the belt at the front pulley would tilt upwards on the left side slightly where it would ride up the lip on the pulley and then slip down

Ok, that is a GROSS misalignment. Either that bike has been wrecked, someone didn't know what they were doing with the rear wheel alignment, or the motor tweaked in the frame. The belt should not be able to ride up on the flanges ... ever. Moving back and forth under coast and drive is pretty normal. As stiff as the swingarm is, it can still twist a little under load. First and foremost, the shafts must be parallel -- adjustment of the motor and/or wheel axle so that they point in the same direction. Second to that and less important given the span is the offset -- adjusting the motor and/or wheel axles along their axes. There is no adjustment for this at the wheel unless you make shims. This adjustment is built into the motor and done by the factory.

By the way, since you describe seeing the belt riding up on the flange of the motor pulley and given the span between pulleys, I strongly suspect your motor is tweaked. Looking down from the top, if you saw the belt climb up the outer flange, you would need to rotate the motor clockwise and vice versa for the inner flange.

That almost sounds like mine when the belt gets wet but not quite the same groan, but that does suggest something with the belt engagement. Looking at the history on this post, it's unfortunate you already messed with the mounting of the motor. Shy of being in an accident, there's NO reason to mess with that and unlikely you'd be able to match what they did in the factory.

How tight is your belt? If I knew nothing else, I'd say your belt was jacked way over tight. And I'd say to check bearings, but I have come across bearings that were on their last leg, could be heard when driving, but that you couldn't feel rolling by hand under no load. It's rare though. You can usually feel a notch at least somewhere around the race.

Audio would be helpful. I have no idea what you would consider an "awful" noise, but the amount and type of misalignment you could get between motor and wheel on a Zero without specifically trying to misalign them would not make much if any noise. Timing belts run up against their flanges all the time. These belts are notorious for making noise when wet, and any timing belt will be noisy if there is too much tension or damage to the belt or a pulley. Misalignment within reason generally impacts on longevity of the components.