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Old 05-09-2013, 06:09 AM   #1
Captdan OP
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R90/6 front break problems

Recently I noticed after a ride of 10-15 miles my front break becomes locked. So much so that in order to get home twice I've had to unscrew the adjustment on the hand lever to " buy" more clearance between the caliper pads. I can get home and after the bike sits for an hour or so ( cooling the break fluid ) she's fine again. I've adjusted the caliper via the cam adjustment to insure it is positioned correctly in relation to the disk. When doing this I noticed the caliper does move back and forth ( from side to side). Curious, is this movement normal? Never had an issue with the from break before, now I can't seem to ride anywhere without an issue, any ideas would be appreciated...
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Old 05-09-2013, 06:30 AM   #2
bmwrench
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Yes, it's supposed to move. The ATE caliper has only one piston, so the caliper rotates slightly to brig the inboard pad into the rotor.

There are several possibilities for the brakes dragging: The cable adjustment may be pushing the master cylinder piston past the vent port, or the port itself may be plugged. Less likely is a collapsing brake hose.

Do solve this problem before riding the bike any more. This is not a minor problem. It could get you killed.
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Old 05-09-2013, 09:04 AM   #3
trc.rhubarb
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I'm going with water (moisture) in the fluid. Water gets hot, turns to steam, puts more pressure on the fluid and locks the brake. Cools down, all is fine again.
Blocked return port would be second on my list but a quick flush of the system is easy and cheap if it fixes it :)
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Old 05-09-2013, 09:18 AM   #4
disston
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1...Blocked return port in the master cylinder piston. Take apart MC and clean the piston. If you are lucky you can get away with out having to buy the seal kit which contains a new piston and is not cheap.

2...Poorly adjusted cable.

3...Collapsed hose.

That's what it sounds like to me. I have never heard of water causing this. We get brakes with water in them all the time. The water causes rust. Brake Fluid is friendly with water. It absorbs water out of the atmosphere. Which is why we change our brake fluid once a year.
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Old 05-09-2013, 09:39 AM   #5
Captdan OP
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Thanks gents, all good info, I think I'll take it apart this weekend and see what I can find. A flush and new fluid can't hurt...
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Old 05-11-2013, 01:38 PM   #6
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Bike fixed?

Well, I took apart the master cylinder, cleaned and flushed the system. All went well on a test ride - but as soon as I rolled back into the driveway the bike died. No power, dead! I though I hit the emergency kill switch, fiddled with it and turned the key on and off. The bike came to life and I cranked it. Then as I rolled into the garage she died again... This time nothing, dead as a door nail. Checked the ground, battery is good... Have not dug into it yet. May not be related, but I took off the tank so see if I pinched a wire... Nothing aparent. Bike stopped good and released the break pads well... But now she won't run.. :(
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Old 05-11-2013, 04:29 PM   #7
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One of the rules of mechanics is to always check what you worked on last when something new happens. So this says that it is very likely you accidentally disturbed one of the wires next to the Master Cylinder. Check the Black wire to the right hand coil. This is from the points and provides the signal that fires the points. The Blue/Green wire to the left coil is Hot when the key is on.

Then again it could always be something new too.
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Old 05-11-2013, 05:07 PM   #8
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Sometimes brakes break.

Hopefully, you resolved that.

Won't run-something simple like the petcock or fuel line? plug/coil wires?
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Old 05-11-2013, 07:30 PM   #9
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Quote:
Originally Posted by ozmoses View Post
Sometimes brakes break.

Hopefully, you resolved that.

Won't run-something simple like the petcock or fuel line? plug/coil wires?
It was dead, no power, nothing, won't even turn over. I checked the wires under the tank and wound up with nothing. Then I removed the headlight cover and decided to start with the ignition switch. I removed the red connection and tested it, had 12 volts. So, switch on and tested the green lead to see if the switch was bad or not. As I tested the spade connection ( and found 12 volts with key on) I heard a " click" somewhere in the headlight bucket. Now the bike starts and runs... Not the kind of fix I like... Can't tust it around the block ( yet).
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Old 05-11-2013, 07:38 PM   #10
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Sometimes, its hard to get a break !
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Old 05-11-2013, 07:56 PM   #11
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So, you suspect the ignition switch. Clean up the connections?

Odd thing, first ride of the season one year my /7 just died, no power. Coasted home ( always start the season UP-hill!) and had lights,etc; hmm? Turned out the hot to the horn was shorting.
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Old 05-11-2013, 08:08 PM   #12
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I've had the brake light switch lugs short on the handlebar through the rubber cover due to a shift in the brake lever perch. If I remember correctly it blew the main fuse (but I may be wrong as it was a long time ago). I always make sure to adjust the switch so the lugs are as far away from the bars as possible.

I think the '74 was the only /6 to run the lever switch instead of the pressure switch for the brake light.
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Old 05-11-2013, 09:33 PM   #13
disston
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I don't put my bike away for the Winter. I ride all year round. Therefor I don't have birthing problems at the beginning of the season..

You gotta get tough.
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Old 05-12-2013, 03:27 PM   #14
Captdan OP
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Just took the r90 on a short 25 mile back roard trip. Ran like a bat, and stops great. Let's see, I took the master cylinder apart, flushed, and cleaned it but never noticed anything out of the ordinary. When she died and had no power I Simply started trouble shooting and she came alive... In the end, fixed nothing definitive, or at least anything I could put my finger on that was wrong... But she's back in action!
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Old 05-12-2013, 03:30 PM   #15
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Great!

But looking at your sig line begs the question-how's that /2 runnin'?
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