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Discussion Starter #1
OK - it's hard to resist opeing up that throttle on the maiden voyage of the season. I admit, despite my considerable advanced age (Truman was in the White House at my birth...OK!), that I am weak in that regard.Perhaps, I should have put the Norton Commando on the road before the K-75, but noooooooooo.... I actually wanted to prep it for the Minuteman 1000 next month.

So, I am crusing along about 85 on a major interstate not far from my home berth, when I hear and felt a very distinctive "pop" from the front end of the bike. All right, I commence emergency responses - slowly back off the throttle to make sure that I still had control; check rear views to make sure that I had a clear shot to the shoulder and set my senses on high alert assessment mode. But - everything seemed fine - or at least, I thought so. No ABS lights, no smoke, no wobble. Could I have imagined it? Was it my chinstrap banging against my helmet? So, I did the logical thing - right? I kept going - what was I thinking!

Four miles later, I was banking into a turn off the Interestate on my exit, again, Spring fever excess overwhelming rationality - I was going too fast! That's when just beyond the apex, I made the chilling discovery that I had no brakes - nada! The front brake lever was free of any resistance. I downshifted and let the throttle braking bring me to a more sensible speed. Now, that I had straighted up and out, I stood on the squishy rear brake and was able to slow it down to a manageable speed and made it home.

I jumped of the bike, kissed the ground and threw my helmet in a rage at my own stupidity for not checking out the bike after the "pop". I should have known better. However, my personal rant at myself gave way to a head shaking "wow". There was brake fluid all over the front wheel and right fork. I then noticed that the bleeder value on the Brembo was actually SHEARED OFF! What the heck! So, your theories would be appreciated...I want to make sure that it is not a systemmic problem!


Thanks
 

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Lucky guy. :clap:

We'd like to see pics of that. So "sheared" or "popped out" that bleeder? Just sheared at the caliper, the oil shouldn't come out unless you are talking "Filler adapter" like some of them bikes have? If "Filler adapter" , I am pretty sure you can take the remnants out and replace it with a regular bleeder, cheaper too. Someone will tell you. :thumb:

My big question.....was the brake system hot? Binding calipers can build up a lot of pressure in the brake system from the oil overheating. Don't ask me how I know that, but that wasn't on a bike, same system anyway. :yeow:

For myself....it pays to test them braking systems especially after a lay-up. Just hit the brakes as hard as you can and hold them there for a minute or two, without the bike moving of course. :) Then inspect everything for leaks or difformations on the hoses. Then go ride, but test on the road too.Much safer a busted hose (Bleeder...) in the yard/shop than on the road at 85.Not foolproof them tests at standstill, something can still happen later but....probably saved my butt a couple times! :yeow:

So...Old enough to remember rusty american junkers pre 65 with single master cylinders? :eek:ldster: :teeth

Saluti Primum..... ! :thumb:
 

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"despite my considerable advanced age (Truman was in the White House at my birth...OK"

Advanced age?? What is that? I am in my middle aged years, born in 1937.
You are one lucky person even if you are of an advanced age! Brakes gone at 85mph. Taming the beast decelerating and then driving home.
Bless your lucky stars my friend!
 

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Discussion Starter #5
Photos of Sheared Bleeder Valve

Hopefully, these images come through. Several of you have asked to see a photo of the sheared caliper bleeder valve and with any luck, they will appear below:

Once you see the images, you will understand why this remains such a mystery. I don't see how the pressure could have built-up to the point, that it blew the top nipple off of the valve. It also appears that there was a force that came across the top of the valve - all that I can think of is that it was some sort of projectile - perhaps alien in origin!
 

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That looks more like a line fitting than a bleeder. And a bleeder has to be unscrewed some to release pressure. Maybe the wheel picked up something and tore off the crossover line between the 2 calipers? Look for the other end of the line going to the other caliper (#9)
 

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mystery

Possibly some hunk of road junk jumped up and knocked it off.
 

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Discussion Starter #8
Vent Screw - More Photos

To Chaos et al:

I have attached some more photos to show that it is not a line fitting. It is what BMW calls a "Vent Screw". The Vent Screw is shown as Part #3 on Diagram 34_0637- Front Wheel Brake, ABS. BMW Part # 34211236793. It is definitely the vent screw.

The photos show the vent screw back in the caliper next nto the line feed. The other photo shows the left side caliper with an in-tact vent screw with the rubber cap off of it. Quite a difference between the damaged one and the good one!

It is still a mystery and not having a satisfactory theory is disconcerting to say the least. Perhaps it may have been previously damaged and I never noticed or, on the other hand, I suspect that my ex-wife may have had something to do with this.The last time that I saw her, she did have a ballpeen hammer... I am worth much more dead than alive!

Ride Safe
 

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Fate7 said:
Hopefully, these images come through. Several of you have asked to see a photo of the sheared caliper bleeder valve and with any luck, they will appear below:

Once you see the images, you will understand why this remains such a mystery. I don't see how the pressure could have built-up to the point, that it blew the top nipple off of the valve. It also appears that there was a force that came across the top of the valve - all that I can think of is that it was some sort of projectile - perhaps alien in origin!
There shouldn't be any pressure in a closed bleeder above where it seats and seals in the caliper. Even if the top gets sheared off it shouldn't leak. What happened to you is very freaky.
 

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Freaky allright.... :wtf:

Coming from a mechanical background in a major "rust belt", I have seen so many bleeders broken right off and they never leaked. We broke a few ourselves and had to resort to some sneaky ways to bleed the systems. Road debris maybe, but they are somewhat protected behind the forks like that. Looking at the damage I'd have to say......22 Bullet. :wtf:

But that's just because it seems to be happening these days, and that some kid shot me in the chest with a slingshot in the 70's , a foot higher he would have killed me. Sure did hurt....a lot !!!:(

Question....Was the bleeder loose when you took it out? :confused:

Bugger, I am almost tempted to take Grandpa's 22 out with some old bleeders and test my theory, but getting old, I don't think I can shoot as good as I used to. :D That would also annoy the neighbors........after I had to convince them :teeth :teeth :teeth to stop their shooting a few years back,I did not like their 22 bullets hitting the trees below my house. :yeow:


If that happened to me, I'd certainly look at a lead test kit ,or find a microscope, or maybe even send that bleeder to my sister the Lab Tech for some analysis, too freaky, I'd have to find out for sure. :( :( :(
 

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Fate7 said:
To Chaos et al:

I have attached some more photos to show that it is not a line fitting. It is what BMW calls a "Vent Screw". The Vent Screw is shown as Part #3 on Diagram 34_0637- Front Wheel Brake, ABS. BMW Part # 34211236793. It is definitely the vent screw.

The photos show the vent screw back in the caliper next nto the line feed. The other photo shows the left side caliper with an in-tact vent screw with the rubber cap off of it. Quite a difference between the damaged one and the good one!
Hmmm, not familiar with how the ABS models are plumbed, but I 99% guarantee that is not a bleed valve (or vent screw, as BMW calls it) Compare the bleed valve nipple on the other caliper to the damaged one-very different in the shoulder, but the damaged one looks identical to the line fitting adjacent to it. If you unscrew it I bet you can remove the flared end of the broken line. If it is a line, the other end of it must be dangling somewhere. Makes more sense that a line could be ripped off than just a nipple. Also, bleed valves have a pointed solid seat with a hole drilled in the side-it couldn't stand upright as in the first photos you posted. Nice pictures, good luck figuring it all out :confused: (and afaik whatever happened is first!)
 

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Discussion Starter #12
Bullet Theory

I am with you on the bullet theory. I don't tend to be conspiracy guy - but for some reason the second shooter on the grassy knoll came to mind. If you could see it up close, you would immediately conclude the same. I will hang onto the vent screw for storytelling purposes. Lead testing? I am not sure I even want to know...






H96669 said:
Freaky allright.... :wtf:

Coming from a mechanical background in a major "rust belt", I have seen so many bleeders broken right off and they never leaked. We broke a few ourselves and had to resort to some sneaky ways to bleed the systems. Road debris maybe, but they are somewhat protected behind the forks like that. Looking at the damage I'd have to say......22 Bullet. :wtf:

But that's just because it seems to be happening these days, and that some kid shot me in the chest with a slingshot in the 70's , a foot higher he would have killed me. Sure did hurt....a lot !!!:(

Question....Was the bleeder loose when you took it out? :confused:

Bugger, I am almost tempted to take Grandpa's 22 out with some old bleeders and test my theory, but getting old, I don't think I can shoot as good as I used to. :D That would also annoy the neighbors........after I had to convince them :teeth :teeth :teeth to stop their shooting a few years back,I did not like their 22 bullets hitting the trees below my house. :yeow:


If that happened to me, I'd certainly look at a lead test kit ,or find a microscope, or maybe even send that bleeder to my sister the Lab Tech for some analysis, too freaky, I'd have to find out for sure. :( :( :(
 

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But you never answered my question....was that "Bleeder" loose when you took it out? :confused:

If NO, you can forget the grassy knoll theory, just my weird logic talking sometimes, and you got to have fun with some of them posts. :D

I did have some suspicions as to "what" is really in there on your bike, did someone jury rigged something to get himself going after loosing the proper bleeder in the shop/grass/gravel, then forgot( :D ) to buy/install the proper part. :(

Then what else could be screwed up in that braking system. I hope you also have the rubber caps on the bleeders, them missing is asking for other problems down the road. :(

Just to follow on Chaos's post and some clarity....those are BMW OEM Bleeders!

 

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FWIW, on the ABS systems I've seen on the S, the line from the master feeds into the right caliper, then jumps over to the left, where the bleeder (vent) is. The picture here has a SS line but the plumbing is correct. If your bike had this system, the line from the right caliper to the master somehow got torn off.
 

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