Weird scraping noise while rolling rear wheel

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crcfailed
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Weird scraping noise while rolling rear wheel

Post by crcfailed »

Hey guys!

I appreciate your previous help with my "beginner blues." My new Buddy has been a lot of fun, and I'm really happy I bought it.

I just rolled the odometer over 100 miles so I'm officially in Phase 2 of break-in. Right when I got home and backed the scoot into the garage, I noticed a weird scraping feeling/sound that I don't remember being there before. It's hard to tell exactly where the sound is coming from, but it's definitely from the rear somewhere, and I'm afraid it may be coming from the engine but I'm not sure. I'm really worried! My poor baby Buddy! :(

Can anyone identify what this might be???

While rolling the scoot back and forth on the ground.
https://photos.app.goo.gl/GFFT89jknJ1c86Ts6

While free spinning the rear wheel back and forth on the center stand.
https://photos.app.goo.gl/3xD37wdJatmBe4JJA
(Note: Sorry about the cicada & cricket sounds in the background.... but if you listen closely you might notice that in addition to the scraping noise there is an occasional squeaking sound coming from the bike that is very similar sounding to the crickets.) [/url]
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crcfailed
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Post by crcfailed »

Forget everything I said. The reason I was so confused by the noise was because I misperceived where it was coming from. It wasn't coming from the rear at all - in fact, it was the front disc break!

So the question is, why is my front disc brake scraping suddenly? Did I jack up my fork or my wheel already from hitting a bump or something? Maybe this is normal, and I need to adjust the brake?

I tried to take some video of the brake in action but it wasn't any help to me. There are no exposed moving parts to the brake that I can see, so it is much different from the cable-operated bicycle brakes that I am used to working on. There also seems to be a slight wobble, as the scraping is not consistent throughout the circumference of the wheel but is pronounced in only one or two spots.

I did have to brake really hard earlier this week, because some guy decided at the last minute he didn't want to be in the left turn lane, and pulled straight across my lane not more than 2 or 3 car lengths ahead of me. I barely missed him. Lucky there was no one behind me or I would probably have been sandwiched. However, the scraping did not start until just today suddenly, and nothing out of the ordinary happened on my last trip.
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charlie55
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Post by charlie55 »

As for the front wheel.....

Generally speaking, a cyclic or steady brushing sound when manually rotating a wheel with a disk brake is not unusual because the disk isn't spinning fast enough to throw the pads aside. However, that metallic "ffftang-ffftang" doesn't sound right to me. Three things come to mind:

- Warped disk rotor (highly unlikely in a new scoot). Get the front wheel off the ground, watch the rotor from dead ahead as you rotate the wheel. If it appears to be wobbly in relation to the wheel itself, then it's warped. You actually need to measure this type of problem with a run-out gauge to be sure.

- Blown wheel bearing. Repeat the test above. If the wheel and the rotor are wobbling in sync, then you may, repeat may have a bad wheel bearing. However, you really need to determine if the sound is coming from the disk rotor/caliper or the part of the wheel the axle passes through.

- Debris embedded in the brake pads. Sometimes you can pick up small bits of gravel or other road crud that gets stuck in the brake pads. Check your disk rotor to see if there's a noticeable score (scratch) running around the entire circumference of either the outer or inner (you might need a mirror for this) face of the rotor.

Now, that "pffft-whoosh" sound you get when only rotating the rear wheel - that has me bugged too. I'm neither a Buddy nor 2-stroke owner, but it sounds to me as if your rear wheel is turning your engine over and thus moving the piston up and down. That shouldn't be happening with a CVT transmission because the clutch should be disengaged. Maybe this is normal for a Buddy 50, so I'll defer to those having more knowledge than I in this case.''
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crcfailed
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Post by crcfailed »

Thanks for your comments. I went ahead and tried to check the things you mentioned.
charlie55 wrote:- Warped disk rotor (highly unlikely in a new scoot). Get the front wheel off the ground, watch the rotor from dead ahead as you rotate the wheel. If it appears to be wobbly in relation to the wheel itself, then it's warped. You actually need to measure this type of problem with a run-out gauge to be sure.
While my garage equipment is pretty limited to stuff to do with bicycles... what I did was I tilted the scooter back on the center stand and propped it up with some scrap wood. I set my phone camera under the front wheel and recorded while giving the wheel a few revolutions at several different speeds. No noticable wobble on either the wheel or the disc, so I guess that's good. Since I don't have one of these run-out gauges that's about as far as I'm going to get on my own. (Didn't bother to upload this video as there's not much to see.)
- Debris embedded in the brake pads. Sometimes you can pick up small bits of gravel or other road crud that gets stuck in the brake pads. Check your disk rotor to see if there's a noticeable score (scratch) running around the entire circumference of either the outer or inner (you might need a mirror for this) face of the rotor.
The rotor looks a little scraped up, but the scraping is evenly distributed and I don't see any scour marks or rings that stand out. Nothing I wouldn't expect to see on a bicycle equivalent.

I tried shining a flashlight through the caliper straight between the pads and the rotor, to see if the photons were blocked at any point. I did not notice any blockage or scraping near the bottom of the pads, but this actually turned out not to be a very good test because I think the arc of the caliper housing may be blocking the upper portion of the pads anyway. It's hard to know exactly what I'm seeing down there because of the fork, rim, etc. all being in the way.

What I do see, though, is a bit of yellow coating, like paint maybe, which has scraped either onto or off of the outer bevels of the rotor. Some of it was loose and I was able to brush it off with my hand, but there was not a lot of it. Incidentally, my disc brake lock is yellow, but I think it's highly unlikely that it transferred paint only to the edge of the rotor like that.

My best guess is that the top of rotor is actually scraping the roof of the brake assy somehow, and I wonder if something is out of whack up where the pads mount. However, taking the weight off the front wheel doesn't seem to make it any better.

My number two guess is that while I was in Walmart, someone was screwing with my scoot and tried to pull it away with the disc lock on it, and in doing so, jacked something up with the front wheel somehow. If they DID, I certainly didn't notice anything else weird other than the scoot being parked a lot farther back than I remember. (Maybe it's just me.)

Or maybe it's just stuff settling into place, as it IS a brand new scoot.
Now, that "pffft-whoosh" sound you get when only rotating the rear wheel - that has me bugged too. I'm neither a Buddy nor 2-stroke owner, but it sounds to me as if your rear wheel is turning your engine over and thus moving the piston up and down. That shouldn't be happening with a CVT transmission because the clutch should be disengaged. Maybe this is normal for a Buddy 50, so I'll defer to those having more knowledge than I in this case.''
Yeah, I don't know much about these things myself, obviously, but I'm less worried about the rear at this point. Whatever it is, it's probably normal, and I was just distracted and confused trying to figure out where the scraping noise was coming from.

The brakes seem to be working fine. I checked where the hose attaches to the brake assy, and there isn't any apparent leakage.

At this point I've got a little less than 100 miles left until I'm due for my first scheduled maintenance at 200 miles. I'm thinking if this is not a big problem, I can just bring it up then. If it's just a pad rubbing, I'm guessing it will wear down by then but who knows...
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crcfailed
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Post by crcfailed »

Just a quick update, I was inspecting the scoot getting ready to ride to church this morning, and noticed the scraping sound has just gone away after a day of sitting in the garage. Rode it to church and back, still no noise. Weird!

Maybe the awful humidity the past few days caused something to expand. Guess I may never know unless the noise comes back. :P
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Post by jrsjr »

I did a bunch of digging in the archives to see what I could find that might be relevant. Every thread that I found that had a resolution (and most of the suggestions from mechanically knowledgeable folks) revolved around wear items - bearings, variator rollers, clutch springs and, in one case, a seriously over-tightened axle nut. None of these problems should be the case with your new B50.

For that reason, I strongly suggest that you bring it to your dealer should the noise reappear. I emphasize that because in a couple threads I found, the mystery noise went away on its own, but then returned after a couple days.

If the noise never reappears, I'm stumped and your dealer probably will be, too. It's very difficult to troubleshoot a noise that isn't there. It would still be worth mentioning it to the service writer next time because sometimes a mechanic can spot obvious problems that are not apparent to a non-mechanic. That happened to me one time during a safety inspection. I had over-tightened a critical nut (I'm a stupidly bad mechanic, sorry to say) and when we talked about the bike the mechanic noted something I said and immediately went and spotted the problem in a heartbeat. So, you never know. It's certainly worth a mention.

When you figure this out, please post the resolution here! That's how we as a group learn.

Cheers!
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