OP
Tue, 07 Mar 2023 06:00:03 +0000

Enthusiast
Piaggio MP3 500
Joined: Wed, 21 Jul 2010 01:45:55 +0000
Posts: 56
Location: Los Angeles
 
OP
Enthusiast
Piaggio MP3 500
Joined: Wed, 21 Jul 2010 01:45:55 +0000
Posts: 56
Location: Los Angeles
Tue, 07 Mar 2023 06:00:03 +0000 quote
Anybody know what can possibly cause front wheels to lock up, the front brake lever to go stiff while riding?

I was riding around and all the sudden the bike locked up like that, to the point where I can't even turn the bike off and push it. I started the bike back up, let the bike rest for a bit, then the lever would loosen up slightly, and I tried revving real hard to overcome the brakes, sometimes it would allow me to do so for a while, and I'd be able to move the bike forward for a while, but as the bike decelerates, it would almost always start to stiffen and lock up entirely again.

Any clues what can be causing this problem?

I also hear some sort of small grinding noise in the front.
Tue, 07 Mar 2023 06:34:54 +0000

Ossessionato
2019 GTS300 Supertech E3 44,000km
Joined: Wed, 18 Nov 2020 02:36:54 +0000
Posts: 3150
Location: Batmania aka Melbourne, Australia
 
Ossessionato
2019 GTS300 Supertech E3 44,000km
Joined: Wed, 18 Nov 2020 02:36:54 +0000
Posts: 3150
Location: Batmania aka Melbourne, Australia
Tue, 07 Mar 2023 06:34:54 +0000 quote
ABS unit failure?
Tue, 07 Mar 2023 13:54:57 +0000

Ossessionato
Gilera Fuoco 500ie
Joined: Sun, 11 Oct 2009 13:35:31 +0000
Posts: 4427
Location: Netherlands Olst
 
Ossessionato
Gilera Fuoco 500ie
Joined: Sun, 11 Oct 2009 13:35:31 +0000
Posts: 4427
Location: Netherlands Olst
Tue, 07 Mar 2023 13:54:57 +0000 quote
aftermarket or left brake lever on the right handside
Tue, 07 Mar 2023 23:42:02 +0000

Enthusiast
2007 MP3 250ie / 2022 MP3 500HPE SA
Joined: Fri, 03 Jun 2022 22:01:48 +0000
Posts: 51
Location: CCS-Vzla
 
Enthusiast
2007 MP3 250ie / 2022 MP3 500HPE SA
Joined: Fri, 03 Jun 2022 22:01:48 +0000
Posts: 51
Location: CCS-Vzla
Tue, 07 Mar 2023 23:42:02 +0000 quote
Other possible causes, extra to what Maksor says:

1- Brake fluid contaminated / overheated in some point and create a emulsion gel.
Easy way to check: if all returns to "normal" or is better with the brakes completely cold.
Solution: remove and replace all the brake fluid

2- Mix of DOT 5 (silicon base) brake fluid with the DOT 3-4 actual fluid. It generate a gel that leaves the calipers locked.
Easy way to check: only know if happens in a service or by mistake
Solution: remove and replace all the brake fluid (good flush is very important)

3- The level is installed wrong don't avoiding the pressure return (happens to me in the Ducati ones)
Easy way to check: remove the brake level, if the brakes become loose you are in
Solution: Install brake level correctly
Wed, 08 Mar 2023 12:58:05 +0000

Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni, 2008 Vespa S150
Joined: Sat, 13 Oct 2012 12:48:57 +0000
Posts: 8870
Location: Ashburn, Va. Home to the Internet
 
Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni, 2008 Vespa S150
Joined: Sat, 13 Oct 2012 12:48:57 +0000
Posts: 8870
Location: Ashburn, Va. Home to the Internet
Wed, 08 Mar 2023 12:58:05 +0000 quote
One of your calipers is stuck. It's heating up and locking up.
Thu, 09 Mar 2023 00:13:08 +0000

Veni, Vidi, Posti
Neutrino MP3 492.7 AK, 2013 Moto Guzzi Norge
Joined: Sun, 30 Mar 2008 04:38:24 +0000
Posts: 22148
Location: Harriman, Tennessee, Tn
 
Veni, Vidi, Posti
Neutrino MP3 492.7 AK, 2013 Moto Guzzi Norge
Joined: Sun, 30 Mar 2008 04:38:24 +0000
Posts: 22148
Location: Harriman, Tennessee, Tn
Thu, 09 Mar 2023 00:13:08 +0000 quote
did you wear the pads completely to the plates and weld the plates to the rotor?
Sun, 12 Mar 2023 02:14:14 +0000

Hooked
MP3 - 500
Joined: Sun, 11 Jan 2009 23:51:19 +0000
Posts: 427
Location: Alabama, USA
 
Hooked
MP3 - 500
Joined: Sun, 11 Jan 2009 23:51:19 +0000
Posts: 427
Location: Alabama, USA
Sun, 12 Mar 2023 02:14:14 +0000 quote
perhaps open the bleeder valves and pull the brake lever a few times, letting out a portion of brake fluid, have rags handy in place, to catch the expelled fluid. tighten up the bleeder screws, check the b.f. level and fill up if low. Repeating several times may cure the issue

Good luck
Mon, 13 Mar 2023 09:05:37 +0000

Member
Piaggio MP3 500
Joined: Wed, 27 Apr 2022 13:51:23 +0000
Posts: 16
Location: Upstate, New York
 
Member
Piaggio MP3 500
Joined: Wed, 27 Apr 2022 13:51:23 +0000
Posts: 16
Location: Upstate, New York
Mon, 13 Mar 2023 09:05:37 +0000 quote
My money's on a blocked/clogged compensation port in the master cylinder. If the front wheels free-up when you loosen the brake line on the master cylinder (relieving pressure), that will confirm the problem. If you have a bit of free play in the lever, it's a compensation port clog from dirty fluid, etc. If there's no play, you have a lever issue as mentioned by others. Good luck.
Thu, 16 Mar 2023 13:21:55 +0000

Hooked
MP3 - 500
Joined: Sun, 11 Jan 2009 23:51:19 +0000
Posts: 427
Location: Alabama, USA
 
Hooked
MP3 - 500
Joined: Sun, 11 Jan 2009 23:51:19 +0000
Posts: 427
Location: Alabama, USA
Thu, 16 Mar 2023 13:21:55 +0000 quote
Any pics. or diagrams of the compensation port would be helpful

Thanks
Fri, 17 Mar 2023 15:30:44 +0000

Member
Piaggio MP3 500
Joined: Wed, 27 Apr 2022 13:51:23 +0000
Posts: 16
Location: Upstate, New York
 
Member
Piaggio MP3 500
Joined: Wed, 27 Apr 2022 13:51:23 +0000
Posts: 16
Location: Upstate, New York
Fri, 17 Mar 2023 15:30:44 +0000 quote
The compensation port is a small hole in the top of the master cylinder bore. When you release the brake lever, the piston/seals retracts to uncover this hole, which releases any residual pressure in the brake line. If this hole is plugged or blocked (sometimes the piston rod is misadjusted), pressure can remain in the brake line, which causes the brakes to drag or lockup. The compensation port is also called a vent port or by-pass port. Hope this helps.



Sat, 18 Mar 2023 00:14:04 +0000

Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni, 2008 Vespa S150
Joined: Sat, 13 Oct 2012 12:48:57 +0000
Posts: 8870
Location: Ashburn, Va. Home to the Internet
 
Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni, 2008 Vespa S150
Joined: Sat, 13 Oct 2012 12:48:57 +0000
Posts: 8870
Location: Ashburn, Va. Home to the Internet
Sat, 18 Mar 2023 00:14:04 +0000 quote
You can easily test the compensation port by removing a front wheel and see if if you can pry the inside brake pad in with a screwdriver away from the rotor, i.e. compressing the piston back into the caliper.

Pump the brakes to make sure the pads on both sides are seated against the rotors then see if you can pry one of the inside pads away from the rotor.
Sat, 18 Mar 2023 14:28:48 +0000

Hooked
MP3 - 500
Joined: Sun, 11 Jan 2009 23:51:19 +0000
Posts: 427
Location: Alabama, USA
 
Hooked
MP3 - 500
Joined: Sun, 11 Jan 2009 23:51:19 +0000
Posts: 427
Location: Alabama, USA
Sat, 18 Mar 2023 14:28:48 +0000 quote
Terrific illustration plus advice on fixing faulty brakes.

The diagram sure removed a whole bunch of questions about how these things work.

Kinda miss the old cables though, where a spot of grease in the right spot could get things going again........

Many thanks for all the input.
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