Does this look right?

[Quirky]

Sounds daft but the front brake of my speed triple has applied itself twice while I've been riding it, I haven't even been touching the lever. The second time this caused me to lowside the bike, luckily it wasn't at speed.

While the bike has been away getting repaired I've researched the problem. A few people seem to me to have had similar issues caused by the master cylinder piston rod not sitting correctly in lever. I've just got the bike back and now I've got a complex about riding it because I don't know if its safe.

Could anybody tell me if this looks like everything fits together correctly

https://i243.photobucket.com/albums/ff191/Quirky_06/Mobile%20Uploads/20150317_184259_zpsvrgbsbu9.jpg

https://i243.photobucket.com/albums/ff191/Quirky_06/Mobile%20Uploads/20150317_184248_zpscpzjediz.jpg

https://i243.photobucket.com/albums/ff191/Quirky_06/Mobile%20Uploads/20150317_184309_zpshgzxknuf.jpg[/img]

[Fisty]

Looks fine, but if you are over paranoid swap the m/c for a better one.
____________________
Quietly and consistently taking the piss.
TL1000R | Hayabusa | ZXR400 | TL1000S | Bandit 400 V
Fatter and faster than Fret

[Quirky]

I think the m/c is ok. I haven't had the bike long and i know the brake lever was changed just before I bought it so I'm thinking the lever wasn't fitted correctly but its all just guesswork.

[Ariel Badger]

The only way I know that a hydraulic disk brake can self activate is this... The pads are in constant contact with the disk and because friction they get very hot and boil your fluid.
Ask Pete about it, it happened to him a 132 Mph.
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[andys675]

is it a pattern lever or a genuine one?

if it's pattern it may be made badly, and slightly applying the brake in use, does it push the piston in when fitted?

I know of several problems caused by pattern levers, one mate lost his front brake pressure on his blade on track days as the heel of the lever was smaller than OE and it wouldn't push the piston in far enough to operate the brakes when hot, it was fine on the road, a new genuine lever sorted it

then there was that kid with the pattern levers on his street triple, the cheap lever was pressing on the piston so they were dragging, when the brakes got warm they locked up and threw him down the road
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Some people feel the rain, others just get wet.

[STONEY!]

I have seen cheap chinese knock off brembo levers (and others) cause this, the levers are incorrectly made and fit but once bolted on apply slight pressure to the master cylinder piston causing a slight bind of the brakes which in turn does as Ariel Badger says.

[STONEY!]

Damn, beaten to it lol

[Quirky]

Well the lever that was on before I crashed may have been pattern but i couldn't be sure. As far as i know, the one thats on now is OEM.

Thats what I've read in similar stories that ill fitting levers were causing pads to rub and overheat the system. Now the new lever has been fitted by the repairer I'm hoping its sorted but I want to be sure.

If i roll the bike forward I can hear a slight rubbing of the pads but no more than my last bike. How can I tell if its right when the moving parts are hidden behind the rubber boot of the m/c?

[Ariel Badger]

Take it 5 miles up a motorway and pull into services without touching the front brake, if the disk is too hot to touch it is a problem.
____________________
Bikers make great organ donors, get 115 on your licence today.

[Quirky]

I would do that but it threw me off after less than 2 miles last time I used it. Saying that, I don't know how else to test it

[c_dug]

Then do the same but stop after a mile or so? If it got hot enough in that time to lock up you'll feel it.

For what it's worth, in your shoes I'd be selling the bike, I don't think I could trust the bike any more which would take the fun out of riding.

Plenty more fish in the sea.
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[Quirky]

Thats crossed my mind too but I can't sell it knowing I might be passing a dangerous problem on to someone else.

[Taught2BCauti...]

If the pads are binding, as long as the roller is not depressing the plunger when at rest, I think the problem is more likely to be with the seals in the caliper. If they are not allowing the pistons to retract, try stripping and cleaning the caliper, and fit new seals.

You should be able to tell in less than a mile if the pads are binding.
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[Quirky]

Be able to tell as in heat in the discs?

[jjdugen]

Had exactly this problem on an RD 250 I built up a year or so ago.
It was the rear brake that was binding solidly on, a common problem it would seem.
There is a very small 'return' hole in the bottom of the reservoir, this had become blocked with debris.
The cause is that every time you apply the brake the system is pressurised, but can't de-presurise because the return hole is blocked. Result is that the pads grip the disk harder and harder, heating everything up and jamming the brake hard on.
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[Quirky]

Also worth mentioning the first time it happened was after 4 miles, just under 2 miles the second time. Its since been on at least a 7 mile road test with the repairer and they didn't notice anything.

[Pete.]

Yes what Ariel Badger says is correct. If the piston is held in a tiny bit the return port is closed off. Mine was an extreme case since I was shoving the bike along with 400hp so it got very hot indeed and it was 20 minutes before you could even wheel the bike. After it cooled you would not have known there was a problem at all.

Un-wind the span adjuster to pull the lever in towards the bar, then adjust it back out. See if adjusting it pushes the plunger in any at all.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Quirky]

Pete, thats exactly what happened the first time. Couldn't wheel the bike at all. Luckily happened pretty much at my door so managed to get it in yhe garage. 20 minutes later all was good

[Pete.]

There you go, you've found the problem. Now to find the cure.

BTW you could have the wheel turning immediately by cracking a brake pipe union and letting out a little brake fluid.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Quirky]

But if it was a problem with the caliper generating heat, would the same symptoms not occur, ie 20 minutes later its cooled down and returned to normal.

I'll have a look at the lever to see if I can see anything but I am far from technical so could you tell me what I'm looking for as if you were talking to a child?

Out of interest, how far had you gone before the wheel locked up?

[Pete.]

[Pete.]

I just found this page with google images search. It explains the problem and the reason:

https://www.trialspartsusa.com/diagrams/AJP.jpg
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Pete.]

Your problem could be nothing more than the lever hinge bolt done up too tight. This would cause the span adjuster to push on the plunger rather than opening the span.

Squeeze the brakes then let them go. Push the lever away and watch the plunger. If it moves, loosen the locknut on the underside of the lever hinge and un-do the allen bolt a fraction of a turn to loosen the hinge.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Quirky]

The span adjuster being the nut on the rod that goes into the m/c??

If it doesnt move then the problem may have gone with the fitting of the new lever?

[Quirky]

Missed that link. I've just taken a look and I think it makes sense.