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  #1  
Old 3 Mar 2008
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F650GS mushy front brake - ABS

Audrey had a bit of a spill on the Moyale to Isiolo road in northern Kenya where the bike ended up upside down for a few minutes. (check out Audrey and Ekkes Home Page for all the details)

We had Chris at Jungle Junction do a full brake bleed including on the ABS. The front brake is still mushy. Does anyone have any tips on how to bleed the front brakes on an ABS equipped F650GS??? Thanks.
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Ekke Kok

'84 R100RT 141,000 km (Dad's!)
'89 R100GS 250,000 km (and ready for another continent)
'07 R1200GS Adventure 100,000 km (just finished Circumnavigating Asia)


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  #2  
Old 3 Mar 2008
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Ekke,

I doubt this is much help but here is an excerpt I found in the F650GS shop manual:


If the vehicle is equipped with
ABS, the brake system
has to be bled using the BMWMoDiTeC, and
the Control Units, Toolbox ABS, routine; this procedure
is supplementary to that described in the Repair
Manual.
If the BMWMoDiTeC is not used there is a danger of
residual air remaining in the control circuits of the
ABS system.

Unfortunately I don't have any info on the procedure.

Since this was a result of a crash I got thinking perhaps the ABS sensor adjustment may have been affected. Here is the excerpt on the sensor adjustment:

Checking/adjusting front
ABS sensor gap
Important:
Check the ABS sensor gap if the ABS sensor, sensor
ring, wheel bearing, front wheel, telescopic fork,
spacer, quick-release axle, or brake disc has been
replaced.
– Take load off front wheel and lift it clear of
ground.
Check gap between ABS sensor (1) and sensor
ring (2) by inserting feeler gauge at three points
offset 120° around the ring.
Adjusting ABS sensor gap
– Gap is larger than 1 mm (0.04 in) at at least one
point.
Remove ABS sensor (1).
Remove washer (3).
– Gap is less than 0.1 mm (0.004 in) at at least one
point.
Remove ABS sensor (1).
Install washer (3).
Important:
After adjusting, check clearance of ABS sensor
round the entire circumference of sensor ring.
ABS sensor gap..... 0.10...1.0 mm (0.004...0.04 in)
Tightening torque:
Front ABS sensor........................................... 9 Nm

Wish I could offer more.

I have been following your trip all the way. What a great adventure!

Cheers,

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  #3  
Old 3 Mar 2008
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Ekke,

Here is the link to The Chain Gang ABS faq.

F650 ABS FAQ

Hope it helps.

baswacky.
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  #4  
Old 3 Mar 2008
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Firstly turn off the ABS, I hate ABS. Then Don't forget there's a piston in there so make sure it moves when the line is squeezed, and make sure it moves both in and out and that all of it's waorking parts are clean and lubed. That means the Caliper parts are doing there job, then look elsewhere for the fault. So if that doesn't fix the problem.....


Make sure the Pads are seated correctly and that they are CLEAN scrub them in warm soapy water also do the same with the Brake Rotar, make sure they are CLEAN CLEAN CLEAN, also make sure the ROTAR is FLAT not warped (check by rotating the wheel and looking). Prob 15%


Check the brake line look for a bulge in the line if so then replace, or tape to hell until you can replace it. Prob 15%


If that doesn't work then maybe there's still Air in the Caliper rebleed BUT make sure the pistons all the way back in the Housing, EACH TIME you pump the Lever, otherwise there will still be air hidden in there. Prob 50%


Reservior or Brake line might not be air tight (splits) and pulling in Air Prob 10%


And as a LAST ditch fault finder, disconnect the hose from the Caliper and pump the hell out of the lever keep topping up the reservior and see if there's a blockage (don't let it run dry). Means you know that there's no blockage.... at the same time seal off the Caliper end of the line with a clip to see is the line leaks you should be able to tell by the amount of pressure in the line. Prob 10%


If you fix it let me know what was wrong, and If you have done all of the above and it still doesn't work then let me know as I will have to alter my cheat sheet of bike fixes.

Lee @ F650 Ride the World - A journey of Global Proportions
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  #5  
Old 3 Mar 2008
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Mate, I wouldn't worry about the ABS when bleeding the brakes. I would have replied on the ADVRide as well, but I'm logged in here now.

Assuming you haven't got a leak in your lines (not likely with steel hoses) it sounds like there is still some air in the system. Short of re-bleeding it there are 2 tricks I have used and know.

Firstly, keep the brake applied with some zip ties overnight and see how it is. OR
Secondly, take off the brake bracket from your handlebar and hang it up as high as you can overnight or longer. This should take the bubbles into the reservoir instead of your tubes.

I reckon the ABS things is a lot of BS. It's such a small amount of fluid and like mention on ADVRider, I don't know of a dealer that does it. I would change it like normal and let the ABS kick in on a test ride and bleed again. But only if it's very dirty.

Good luck, I'll keep your blog as another reference of a F650 on a round the world trip.
Be sure to leave feedback on here about things out of the ordinary (not ABS, waterpump or fork seals) that went wrong. It would sure be usefull for other F owners like me that are about to take the bike out on a big one.
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  #6  
Old 9 Mar 2008
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Thanks for the tips!

It sounds like the BMW diagnostic tool opens the circuits in the ABS control module to allow it to be bled properly. I suspect the nearest one is in South Africa. That's quite a ways to ride (through wild animal country!) from Dar es Salaam without a proper front brake.

I will try activating the front ABS on a slippery surface and then bleeding again. Hopefully that helps. If not I'll try raising the master cylinder as well as tying it off under pressure. These seem to make the most sense to me.

Thanks for everyone's help!
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Ekke Kok

'84 R100RT 141,000 km (Dad's!)
'89 R100GS 250,000 km (and ready for another continent)
'07 R1200GS Adventure 100,000 km (just finished Circumnavigating Asia)


www.ekke-audrey.ca
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  #7  
Old 27 Mar 2008
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Still mushy!

Thanks for the tips but it looks like Bill is the most correct. I tried everything I could myself but without any success. It was a lot of fun riding at speed on sand and then jamming on the front brake as hard as possible though!

The nearest BMW dealer is in Windhoek, Namibia so we are going there to have the technicians use the BMW computer to open the valves in the ABS module while bleeding the brakes. Hopefully there won't be too many close encounters with elephants on the road there...
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Ekke Kok

'84 R100RT 141,000 km (Dad's!)
'89 R100GS 250,000 km (and ready for another continent)
'07 R1200GS Adventure 100,000 km (just finished Circumnavigating Asia)


www.ekke-audrey.ca
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  #8  
Old 27 Mar 2008
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Hi Ekke, I was in the BMW dealer of Windhoek in 2006. It is a very small shop with somewhat limited services. I was able to get a spare rear tire for my journey northward, but the shop was not very well equipped at the time. I- and several others- have had some problems with work done at the Jungle Junction. I'm not sure whether it is better to let Chris perform work on your bike or go to the pricey KTM dealer in Nairobi- not far from the the Jungle Junction. If you can make it to Ethiopia I can provide you with information for a solid mechanic in the process of opening a KTM dealership. He's a good man and knows bikes. Chris (at JJ's) knows bikes but is busy doing many other things most of the time. Safe journey! Hook.
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  #9  
Old 27 Mar 2008
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Maybe Chris (nice guy BTW) is a bit outdated?
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  #10  
Old 27 Mar 2008
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That's really weird, because I just had similar problems with my front brake. Talk about karma, but all the things I suggested worked. My problem turned out to be the banjo bolt loosening causing a weep at the bolts. Re-tightening didn't work because the crush washer was worn out. I replace the washers with what I could find which turned out to be with a slightly smaller OD but same ID. Tried heaps of things, thought the hose might have been leaking. Just couldn't get the pressure back on. So I took it into a bike shop and they replaced the washers with some they had which were nearly twice as thick and alluminium (although that shouldn't matter) and just a bit bigger overall. Same ID though. He had to re-tighten it twice but got the right crush in the end. Seems to me like there is a bit of a trick to it. I know I couldn't get the right crush and I really tightended the crap out of it. Had the lever pulled in overnight on the side stand so the cylinder is definately the highest point and it's all back. Before I brought it in I also rode down the street to let the ABS kick in, and I'm confident that's enough. BMW here don't even open the ABS valves and don't know how to do it either.

I know it's frustrating, I fiddled all easter on it and got so fed up I let someone else do it on Tuesday. Sucks being defeated eh. I'll give it a good run this weekend.
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  #11  
Old 30 Mar 2008
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Chris is a good mechanic

Chris at Jungle Junction is a great mechanic. I watched him working on my bike as well as Audrey's. Like any Airhead specialist he has his opinions of course! I don't think that he is outdated, he simply doesn't have the computer necessary to do the proper work. He was sending the computers from a couple of 1200GSs down to South Africa for software updates simply because he doesn't have the equipment.

It is disappointing to hear that the Windhoek dealer isn't all that good. The next closest is in Pretoria but we don't really want to go straight south through Botswana just to loop back up to Namibia. Maybe we'll try Windhoek and if it doesn't work out we'll go down to Cape Town.

I've bled the brakes again here at the Safari Lodge camp near Victoria Falls. I hope that the fix helps for a few more days.
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Ekke Kok

'84 R100RT 141,000 km (Dad's!)
'89 R100GS 250,000 km (and ready for another continent)
'07 R1200GS Adventure 100,000 km (just finished Circumnavigating Asia)


www.ekke-audrey.ca
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  #12  
Old 20 Apr 2008
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Thumbs up Brake Fixed!

Dieter at BMW in Windhoek replaced the master cylinder with a known good used one and we're away! I guess when the brake lever was bent in the fall it tweaked something inside the master cylinder. When I showed Dieter the information about using the MoDiTec he said that was used only to measure the brake pressure, not for opening any valves in the ABS module.

The bad news is that when we came back from a round trip to Swakopmund on some badly corrugated roads Audrey found that she could flat foot the bike! A blown shock. We've found a used one here in Windhoek and get it mounted on Monday. New ones are over N$8,000 (about $1,100 Cdn)! Too bad aftermarket shocks aren't easily available here... Oh well, we got 55,000 km on this last stock shock, heavily loaded on some of the roughest roads in Africa.
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Ekke Kok

'84 R100RT 141,000 km (Dad's!)
'89 R100GS 250,000 km (and ready for another continent)
'07 R1200GS Adventure 100,000 km (just finished Circumnavigating Asia)


www.ekke-audrey.ca
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  #13  
Old 20 Apr 2008
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Hi Ekke,

Good to hear you're back on the road, sorry to hear there was actual physical damage though. A bid concerning.
There is a thread on the Chain Gang about this diagnostics tool that is able to open the valves.

Here here is the thread on the chain gang.

Sucks about the shock as well. You good awesome milage out of it though. A lot of guys have it go at around 25k apparently. I'll be changing mine to a Wilbers before I go.
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  #14  
Old 22 Apr 2008
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Brake's good, used shock not so much

Dieter installed the used shock (supposedly with only 8,000 km under its belt) and it seems pretty much the same as the old one. Audrey can easily touch the ground and when we rode two up (while my bike was getting new tires) it bottomed on even the smallest bump. Drat. What a waste of $700!

The tool that opens the ABS valves for purging is an aftermarket device. Do you know if the BMW tool (MoDiTec) does the same thing? According to Dieter all it does is measure brake pressure, it doesn't open any valves. I can ask again at the Cape Town dealership when we get there just to confirm.
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Ekke Kok

'84 R100RT 141,000 km (Dad's!)
'89 R100GS 250,000 km (and ready for another continent)
'07 R1200GS Adventure 100,000 km (just finished Circumnavigating Asia)


www.ekke-audrey.ca
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  #15  
Old 23 Apr 2008
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Is that still there!

I'm impressed, most the the chain gang ABS FAQ I wrote back in about 2000 is still there! Glad they improved the pictures though, mine were rubbish.

The spongy feel is NOTHING to do with ABS function. The BMW instructions about the diagnostic tool is related to the fact that they employ rough arsed fitters who don't have a clue who need to look for the bits they broke. The fastest way to find an ABS fault is via the diagnostics, especially when you need green=good, red=bad level screens!

Boy, didn't realise I was still so cynical. Best get it over with; IMHO Alan Jeffries BMW in Shipley West Yorkshire UK couldn't find an electrical fault if you gave them Farraday, Einstein and Bill Gates' entire staff to help


Pull the fuse and the four ABS solenoids (two hold, two release for each wheel) spring fully home and you have a conventional, fully effective brake system with exactly as much air in it as before. If they didn't spring back under the 40-100 bar you can apply you'd have a lever you couldn't pull back or one that felt like it had no fluid at all. You'd also have a red light on. A sensor fault is harder for the electronics to detect, but would result in ABS cyling (ie big lumpy brake modulations on a BMW) not a smooth but soft feel.

The problem here is almost definately air in the system. As it remains after the usual bleed procedure you have a leak. The leak might be where the hoses pass through the ABS module, but there is nothing electrical wrong it's going to be a loose pipe or similar. You want to run over all the Banjo's and hoses IMHO. Bleeding via a pump is a lot easier with ABS as there are nooks and crannies in the solenoid block, but enough pressure and/or patience will give results. Holding the lever back overnight works well too.

If BMW decide to charge you a fortune to do anything related to the ABS to fix this, I'd point out it isn't rocket science/brain surgery/black magic and whatever they replace it had better fix it. For some weird reason they always start by replacing the expensive bits

I've not touched a BMW since the incident with the F650 water pump impeller/head gasket in the middle of Morocco, but please feel free to contact me off line if you think I can help.

Good Luck

Andy
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