Brakes WTF

[MaybeGuy]

Ok, on the Mito 350, if I use the front brake, after a while it will gradually bind on until there's smoke billowing from my pads and my disk practically glows. And understandably, the bike grinds to a halt and won't move.

It's happened twice now...

Possible causes?

There's no anti chatter plate in the calliper, but I can't see this making a difference?

I'm using a radial master cylinder, and 4 pot opposed piston calliper
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[jimspeed]

Sounds like the master cylinder is not returning fully,
easy way the check if its that is to release the bleed nipple once the bike has ground to a stop and see if the pressure releases, if it makes no differance then it has to be a caliper mechanical problem like sticking pistons or pads
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Hyosung cruise 125(passed test on, sold) Kawasaki el 252 (better than expected but sold on) Kawasaki GPZ500S first "big"bike.(sold) ZZR600 E5..Z750 2007,ER5, currently on a 2008 Enfield bullet electra x and loving it..
,"Alpha-9: Is there any correlation between dyno rod and dyno kits?"

[MaybeGuy]

[Fizzer Thou]

I have seen this before on many brakes with seized pistons in the caliper.Pump out the pistons evenly using the master cylinder as a pump,remove the seals from the caliper,clean the pistons and reassemble using clean/fresh brake fluid.Should take about 2 hours.

If the seals are damaged do not reuse them-replace them.It is not worth risking using old seals in case of total brake failure.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[MaybeGuy]

[Paddy Blake]

What I do is pump the pistons out near all the way and clean around them then push them in all the way and back on the bike.

If there is a lip on the disc I file the edge of the pads and lightly sand the disc so the new pads wear in fast.

Did you replace the pads or was the bike not used for a while.

[MaybeGuy]

new pads on a stripped and cleaned calliper with an as new disk
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[sickpup]

Radial master cylinder with the lever adjustment all the way out?

What make is the master cylinder?

[Paddy Blake]

Does the bike have a screw on the lever to adjust it so you could let off the pressure for the moment when going about until you sort it.
Make SURE you don't adjust it to where when it cools down you have no brake.

[Fizzer Thou]

A friend fitted a new brake lever that he bought from an accessory shop.It fitted with a bit of a struggle,but he happily pulled up at my place to show me the latest bits that he had fitted to his bike.But it was difficult to push around.When we looked more closely,there was no clearance between the actuating part of the lever and the piston of the master cylinder.Once we had removed the new lever,the actuating piston moved out to its fullest and allowed the bike to be moved around a lot easier.It transpired that the new lever was holding the brake on slightly,pushing brake fluid up into the reservoir and causing fluid lock.Although we took some fluid out of the reservoir,in the end we fitted the original lever and the full travel was returned.

As has been suggested by the others,it does now sound as though there is insufficient free play between the lever and the master cylinder piston.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[Frost]

Even if the pistons are clean, there is often an accumulation of shite behind the dust seals, so it's worth taking them out and cleaning them. Otherwise it's a master cylinder problem.

[DrDonnyBrago]

To me it sounds like the lever is fitted badly or something so that it is applying a small amount of pressure to te MC.

In the MC there is a little vent hole that allows fluid to come back out of the MC and back into the reservoir. This hole is blocked when very little lever pressure is applied allowing the brake system to build pressure when you pull the brakes. If the brakes are being pulled ever so slightly this hole is blocked continually.

An ill fitting brake lever, a dirty/damaged MC and pretty much anything else that might make the lever stick could put just enough pressure on the lever to block the hole but not apply the brakes - from cold it seems to work but when hot the fluid expands in the brake system. The hot fluid has a larger volume but the excess volume cannot leave via the vent hole, the pressure increases and the brakes begin to bind, this in turn makes it even hotter and makes the effect worse to the point that it can lock the wheel.



TLDR - fluid cannot leave the brake system because of a blocked vent hole in the MC so expands with heat locking the brakes.

[Acemastr]

Sounds very much like that bloke who had the Street Triple with the cheapo levers from Ebay that didn't return to fully extended from the bar and blocked a breather(or similar) hole, except his caused him to crash.
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2017 KTM 350 XC-F - 2014 Yamaha R6 - 2005 Yamaha YZ125
2016 Toyota Tacoma Limited

[Grubby]

Have you topped up your reservoir recently? Overfilling can cause this.
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