fyrstormer

iTrader: (1)

I already dropped the transmission, removed the motor, disassembled it, cleaned it, and reassembled it, and the noise still exists. It only makes the noise when the motor is powered; when I roll the vehicle on the floor, the noise is absent.

+ YouTube Video

Any idea what it might be?

CTRJ

iTrader: (13)

Pull the motor out and see if it still does it out of the vehicle.

fyrstormer

iTrader: (1)

I'm not sure I'd be able to hear it without the motor bolted to a solid object that can resonate and amplify the sound. What are you trying to determine with this test?

Mantis Toboggan

iTrader: (4)

Sounds like a brushed motor to me. Most people here probably have never even run a brushed motor so they don't know they are a little noisier. You have brushes contacting a spinning commutator, it is going to make noise. That said, after you cleaned everything, did you lube the motor bearings? You might look into the condition of the commutator and brushes, it might be time to have the comm cut and new brushes installed.

fyrstormer

iTrader: (1)

Yes, I lubed the bearings while I had the motor disassembled. I thought maybe the bearings were rusting because the motor has taken a couple baths while crawling across a creek, but the bearings spun perfectly smoothly. The motor is halfway through its first set of brushes, so I doubt the comm needs lathing just yet.

I know what brushed motors are supposed to sound like; I have several of them in my fleet. This one is making a high-pitched ZZZZZZZZZZZZZZZZ sound that the others don't, and it just started a few days ago. It almost sounded like a twig striking a rotating part, but there was no debris in the motor.

Mantis Toboggan

iTrader: (4)

If the brushes have developed a sharp edge then they could make extra noise. Take a file or some sand paper and round off the leading edge on the brushes.

fyrstormer

iTrader: (1)

Hmm. Okay, I'll take a look at that. I noticed one of the brushes was wearing slightly unevenly but I didn't feel like dealing with realigning the brush hood the last time I had the motor apart. Now that I have two reasons to take it apart again, I guess I'll go ahead and do that.

Actually, make that three reasons. I also found these nifty vented motor-mount spacers on AsiaTees, and after testing them on a different vehicle, they definitely lower the motor temperature in the vicinity of the motor mount because the front of the motor can breathe like it's supposed to. (that's why they put vents on the front of the motor can, after all.)

http://www.asiatees.com/display?bran...=93766&c=brand

fyrstormer

iTrader: (1)

I pulled the motor again, realigned the brush hoods, and resurfaced the brushes. Neither of those steps improved the sound. Then I realized the brushes were able to wiggle side-to-side inside the brush hoods very slightly, and when I wiggled them, it reproduced the noise I was trying to troubleshoot. So it looks like the sound is just caused by the brushes rattling inside the hoods. Not optimal, but not causing any damage either, and I don't feel confident that I could bend the hoods to snug-up the openings without jamming the brushes or otherwise ruining the hoods, so I'm just going to ignore it unless anyone has a good suggestion of how to improve it safely.