'dynamo like' sound front wheel Vespa Sprint
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Joined: 28 Sep 2019
Posts: 9

Sun May 31, 2020 9:20 am quote
Hi guys,

I've been noticing a sound coming from my modern Sprint 125 originating from the front wheel 'somewhere'.

It seems to happen when I've ridden it, not so much when it's cold. (Ie this morning nothing, after 140kms back at home I could hear it.)

The sound can be reproduced when gently/slowly pushing the bike forward or backward, engine off. It's like the onset of a dynamo or cogs or something. It doesn't matter whether the disc brake is hot or cold... it doesn't really sound like a disc squeak either tbh. When you push the bike very slowly it's most noticeable, once rolling the sound is gone/lower frequency - though you can still notice something 'rolling'. I can hear it if I put my ear near the dashboard while on it.

The machine is only 1 year old - with about 6700kms on it, and has recently been dealer serviced and new front tires (120 now), though it's quite possible the sound was there all along but I've never paid attention to it.

Anyone has any ideas? Is this normal?

(I will check with the dealer as well when I get a chance to get there... )
Vespa Sprint 150
Joined: 17 Jan 2019
Posts: 81
Location: Portland OR
Mon Jun 08, 2020 6:02 pm quote
I've got a 2017 Sprint 150. I'm assuming that the front end is the same as the 125. I've never heard anything but the first thing I though of when you said 'dynamo sound' was that it was some how related to the ABS tone ring. I'm assuming that the sound changes based on the speed of the wheel? Looks like the 125's come with at least an ABS option: https://www.vespa.com/en_EN/vespa-models/sprint/sprint-125.html The tone ring is the small ring just inside the disk break, it will have a lot of slats in it (see image below).

hope that helps.
Joined: 16 Jan 2010
Posts: 3623
Location: Tempe, AZ
Tue Jun 09, 2020 3:58 pm quote
[Way OT] The first thing I thought of is that's the Dynamo Hum.[/Way OT]
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 283
Location: Deepinnaharta, Texas
Tue Jun 09, 2020 7:17 pm quote

I couldn't say where she's comin' from...

Yes, ABS ring seems a prime suspect. Consider also the speedometer drive gear going dry.
Joined: 28 Sep 2019
Posts: 9

Mon Jun 29, 2020 6:02 am quote
Thanks for the replies.

I whipped off her bloomers and stiffened my thumb and applied rotation on her sugar plum...

and finally couldn't hear any more dynamo humm.

So yeah - went to the dealer - he sprayed a couple of things into the brakes and afterwards it was gone. He said something about possibly it being dry with some dirt in... Haven't heard it since.
Joined: 28 Jan 2012
Posts: 55
Location: USA
Mon Jun 29, 2020 11:31 am quote
Got a forty dollar bill says it will stay quiet now.
Joined: 28 Sep 2019
Posts: 9

Mon Jun 29, 2020 12:24 pm quote
Yeah did say I didn't want some more
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