Eric here. I am the new owner of a pretty nice 2004 Rockster Tiger Stripe (Black and Orange) with 28,000 miles. I got a nice deal by buying the bike as-is with (among a few other niggles) a failed ABS/Servo system. Symptoms: minimal (residual) braking on the rear brakes, brake warning light steady and ABS light flashing on the dash whenever the brake handle or lever were engaged. The bike had already been diagnosed as a faulty rear servo by the local BMW dealer when I picked it up, and they had already tried a few things to bring it back to life.
After a bit of research, I decided against trying resurrect the system by pulling and cleaning the servo line filters and engaging in a full system flush that has been outlined many times on various sites. My rationale; it seems that too many folks either didn't have success with the process (waste of time), or just delayed the inevitable when the servo system failed again in the future and probably during a less than optimal time (ex: two-up tour loaded going down a steep mountain grade-oh poo!). Knowing what "residual brakes" felt like on the back of this bike, I really never wanted to experience what it might feel like to have the front servo go out on me, as that could easily become a life or death situation. With so many success stories converting the system back to manual, and owning a decently equipped workshop, I decided that more simple on an older bike was better, so i went for it this weekend. Here is the ABS/Servo-delete procedure I followed:
1.) I followed the standard process for tank removal (used a cardboard box with holes in it to keep screws in order-good tip!)
2.) Put plastic sheeting and shop towels over the final drive to catch drips
3.) Removed battery for battery access
4.) Disconnected ABS lines and rear ABS line bracket
5.) Re-plumbled braided flexible brake line with new copper crush washers from the caliper directly to the rear master cylinder
6.) Used lots of absorbent towels, pulled clips and removed ABS lines from top of servo pump unit
7.) More plastic and towels over things, I removed the front ABS lines from the front distribution bracket
8.) Jiggled, wiggled and fished the ABS lines out. I needed to bend one and cut another, probably due to my impatience or worry about drips splashing about that could ruin painted surfaces
9.) Pulled the big ABS wiring plug from brain module by pulling back on the side of the clip and lifting it off
11.) Removed a few additional screws as I recall to pull the servo with brain module out of the bike (it leaks a lot, so I suggest you put it in some type of container afterwards...also be diligent to look for any leaks you may have missed).
12.) I then put the servo pump assembly into a vice and drilled out the four tamper proof screws that hold the brain box (controller) onto the pump. Easy peezy.
13.) Carefully removed the wiring plugs and ribbon connectors from the controller with needle nose pliers
14.) Sealed the bottom of the controller box with several strips of standard (non-conductive) duct tape
15.) Went over the controller bottom and sides again with metallic vent duct tape. Created a 100% solid, air and water tight enclosure
16.) Screwed the controller onto an electrical receptacle blank that was just tad bit larger than the controller body using self tapping screws
17.) Ground the self-tapping screw protrusions from the back of the blank (now the bottom of the controller box)
18.) Coated electrical connector with dialectic grease and reattached it to the controller by pushing the connector on as far as it goes, and then slipping the locking tab back in place. Before you fuss too much like I did to get it to seat, it actually sucks the connector down when you push the locking tab in-who knew?!!
19.) I had just enough extra metal on my over-sized receptacle blank (now the bottom of the controller box) to drill and screw it to the elevated bracket that previously held the ABS pump.
20.) I removed and ground the positioning tab off of bottom of the front ABS distribution bracket (that mounts on the steering head), and cut the unused union (the one with two different sizes in it) from the bracket with a cut off wheel. This gave me better angles to work with.
21.) I struggled a bit, but was able to eventually attach both upper and lower brake hoses (from the reservoir above and to the calipers below) to the distribution bracket using existing banjo bolts and then reattach it to the frame. One again, I used new copper sealing washers on all unions.
22.) Bled the rear brake circuit for approximately five minutes using standard one man, two hand procedure (right hand to pump the brake lever, left hand to open and shut the bleeder).
23.) Bled the front circuit by using first my mighty vac, and then by hand reaching around the front of the bike to operate the brake handle with my left and the the bleed nipples with a wrench in my right. I bled the front circuit, being the most important, for about 15 minutes. I still feel like it has a tad more play than on my R1100RT, maybe 1/4", but they work fine.
24.) Bench tested brakes in place. No leaks and they feel pretty good
25.) Reinstalled battery
26.) Turned ignition on-blue ABS relay in fuse box was clicking away so I pulled it
27.) Brake system warning light still on dash so I disassembled the cluster to access the bulbs (easy) and pulled both brake and ABS warning bulbs for good measure
28.) Remounted the tank and attachments
29.) I broke one of the damned quick connect male-end fuel line fittings so I bought two new stainless steel ones (at an outrageous price BTW, like $80 US inc. tax for two) along with new crimp connectors, removed the old male-end connectors and installed the new ones. That was a very fussy job as the old fittings didn't want to come out of the fuel line, even after warming things with a heat gun. Ugh.
30.) Final reassembly of bike bits
31.) Double checked everything for leaks
32.) Test rode and everything was A-OK! I have heard some people say that they replace the rear master cylinder with a non-ABS model for better power, but I would highly question the need for this. I was able to accidentally skid the rear tire with not all that much pressure and wearing boots, so it certainly sensitive enough!
In hindsight, I probably should have bought a new V-shaped union for the front brake lines (the one for the non-abs model) from the dealer, as the straight angles on the existing piece are a little difficult to work with, but is certainly workable as-is. If you still have plastic male-end fuel quick disconnects, plan on buying metal replacements as they break very very easily and it is probably just a matter of time anyhow until they fail.There is a slight amount of free play in the brake handle which I may be able to adjust out using the lever control wheel, but overall, the brakes felt great, very effective, not nearly as grabby in the front and certainly less annoying with no servo wh
ine now. Oh, and having a rear brake is a good thing too, as long as you don't over-use it like half of the riders I have met!Credit goes to all of those who have documented the process before me, but please don't plan on a wham-bam thank you mam' 2-hour process. I am a meticulous mechanic, ASE certified since 1976 and still invested about 12 hours into the total process including the study of everyone's prior work and write-ups (lots of that), disassembly, retrofit, reassembly and testing when done, not to mention a run to a dealer 45 minutes away to obtain new parts (quick connects) on the fly. On ghat, be prepared to break quick connects if the plastic ones are still in place, finding a knackered or missing blind nut or maybe several, tatty wiring sheaths that need to be addressed and any other number of challenges you may encounter along the way, and addressing each as you find it can be time consuming. Once again, it takes a little time, but it's in the 30'sF now, so what better way to spend the day than in my workshop playing MC mechanic?!
Peace out.
Only had a little wiring trouble during my operation. brown with yellow stripe looks brown. 
think it was still only 2 or 3 hrs.... or to be exact...5 newcastle beers. 
the temps are dropping way too fast. snow, icy roads... very different weather this year vs. last.