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Discussion Starter #1 (Edited)
My 2008 K12GT rear ESA shock stopped working last year. Actually the adjustable preload function stopped working. Rebound adjustment worked fine. Considering the cost of a new replacement shock ($1,800 +), I lived with the issue for a year. I am planning an extended tour this year, and wanted the adjustable preload to allow me to compensate for added load on the rear of the bike, and also because I just like it when all the functions I paid so much $$$ for actually work.

Since the bike is worth maybe $5K, I was not going to spend megabucks to repair this. I have been searching ebay for a year, looking at used shocks as a replacement. Prices ranged from $300 to $500 for a rear ESA complete unit. Last week I noticed one seller with excellent feedback was having a sale for a weekend. $245 including shipping. I pulled the trigger.

I never found a great how to on doing the rear shock for the Gen II GT, but some out there for earlier bikes and related models. I read what was available and dove in.

The idea here is that you pull off the rear body panels and related appendages, and removing some key huge bolts, pivot the rear subframe up and out of the way to reach the shock mounting bolt at the top. Good luck with that. All I can say is there is a LOT of junk to free up before the rear subframe will move. I concentrated instead in taking out the oil tank, which covers the top mount. I spent 1.5 sweaty days taking everything off, including the fuel tank. That night I couldn't sleep and woke really early next day because I was afraid I had taken the bike so far apart I would never get it together. On the second day, I actually got the oil tank out and from there is was not hard to free the shock.

Installation of the new shock, and replacing all the parts I had removed took the rest of the day. With the tank off I tried zapping the non-functioning fuel level strip, not sure yet how that went.

Before putting all the panels back on I tested the shock and Eureka! It worked!

Very happy to have full function ESA again. It will take a few days to get my hands clean, and my leg muscles are paralyzed from crawling around on the bike.

Life is good.

P.S. It appears that the problem with the original ESA unit is in the wiring, as it looks like the idiot at the factory who over-tightens cable ties has struck again. Combined with some iffy cable routing by the factory it seems the wires chafe and then you have a short or open circuit. Indeed, I found a broken wire on the front shock too! The used replacement shock wiring also showed signs of wear at the point where a cable tie would have been on the bike. So - take a look at your wires, they are pretty hard to examine but a little time spent here could save you some grief.
 

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thx for the report. Excellent.

Now, what fluid powers the units? My 13 has the same system.

Next task on mine is checking the rear master brake reservoir. No leaking of any kind, but a mans' "gotta know".

Greg
 

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Discussion Starter #3
thx for the report. Excellent.

Now, what fluid powers the units? My 13 has the same system.

Next task on mine is checking the rear master brake reservoir. No leaking of any kind, but a mans' "gotta know".

Greg
Greg, the ESA on the K13 IS almost identical to the K12. If you look at the unit, there is a pretty normal gas/oil shock absorber unit that has two electrically driven functions added on (ESA). One function controls rebound (Comfort, Normal, Sport)by electrically adjusting the size of a small port in the shock. The other function controls spring preload (One helmet, Helmet plus Luggage, Two Helmets), and that function is controlled by an electric motor that actually winds up the big spring on the shock.

Another option if the shock absorber itself fails and the ESA is still working is to rebuild or replace the shock. I did that on another bike (R1200GSA) where the oil leaked out (failed oil seal) and had a Wilber shock installed ($750). Worked great.
 

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Thx. So far, with the compu screen showing me the setting is on Normal I'm not convinced the shock works as it ought too.

Else-wise things are set for one rider.
 

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Discussion Starter #5
Thx. So far, with the compu screen showing me the setting is on Normal I'm not convinced the shock works as it ought too.

Else-wise things are set for one rider.
Sit on the bike, with the side and center stands up. Put the bike in neutral and start the engine. Press ESA button once to show the settings on the screen. You said yours show Normal and one helmet. Press the ESA once briefly to cycle through the Normal, Sport and Comfort settings. Then Press and hold the ESA button for a few seconds and release it. The one helmet + luggage symbol should show and then flash a few times and then display a solid one helmet + luggage. If you pay attention you may notice the bike rising up slightly in the rear. Press and hold the ESA button again and it will go into two helmets and the rear will rise slightly again. Repeat to cycle back to your original setting.

That's all there is to it. When riding, I can definitely feel a difference in the Comfort, Normal and Sport settings - the suspension gets a little tighter. As I said above the preload adjustment when adding luggage or a passenger is obvious with the height change.

If you have the GS911 device you can read out any error codes that are generated by electrical faults such as I had.

Good luck
 
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I wish things were as simple as @lhendrick makes it seem. Unfortunately, there are multiple types of rear shock for the 2006+ K1200GT and K1300GT.

I have a "late 2007" K1200GT and made the mistake of buying a rear shock from a 2008 K1200GT. The 2008 rear shock and my 2007 rear shock were not compatible. If I had kept the 2008 rear shock, the ESA damping would have worked, but not the preload.

My 2007 rear shock uses a potentiometer, the newer 2008 rear shock uses Hall Effect for the preload position sensor. The on-board computer (ZFE?) on my 2007 will not operate the ESA preload for a 2008 rear shock.

Newer on-board computers (ZFE?) know about the older shocks, so I could have bought a new on-board computer and used it with either the 2008 shock or a 2007 shock.

The final result was that I sold the 2008 rear shock, and had my existing 2007 rear shock rebuilt by Race Tech. See this thread:

http://www.k-bikes.com/forums/30-southern-california/37873-best-rear-shock-installer-la-phoenix-area.html

Here is another thread that discusses the shock replacement issue. See my posts #23 and especially post #38:

http://www.i-bmw.com/showthread.php?t=15296

P.S. There may be more than two types of rear shocks. I also remember the dealer mentioned yet another part number for the 2006 ESA rear shock.

In my opinion, @lhendrick may have been lucky.
 

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Discussion Starter #9
Luck or talent - it all helps sometimes. ;-)

Greg
Oh, it's definitely talent. I was talented enough to buy a 2008 !! Ha Ha! Seriously, I spent a lot of time reading all the posts I could including those referred to by XMagnaRider. I was sure the replacement would work and just had to wait for the right one to show up for sale at a good price. Of course it could have been non-operative for lots of reasons. Buyer beware.

BTW: I needed a new ZFE last year (cold solder joints on the circuit board caused instrument panel drop outs), BMW wanted $850 or so plus labor/codong, so once again I went to ebay and bought a used one off a wreck (same part number) for $55. It worked fine, required no programming by the dealer even though they swore to me it would not work. GS911 shows its there and doing its job with no faults.

When the actual shock absorber component fails or just gets boring I may have it replaced with a compatible Wilber shock and retain the ESA function. I did this on my R12GSA and it works great.

Make your own luck, or as my Daddy used to say, "Fortune is infatuated with the efficient"
 
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Ah I have had the pleasure of some bulging caps on a (non-BMW) circuit board. My solder iron skills aren't that good but it was a freebie so it didn't hurt a bit to toss the piece-a-crap in the dumpster.
 

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Discussion Starter #11
Ah I have had the pleasure of some bulging caps on a (non-BMW) circuit board. My solder iron skills aren't that good but it was a freebie so it didn't hurt a bit to toss the piece-a-crap in the dumpster.
I was actually able to work on the circuit board to address the "cold solder" joints by applying a soldering iron to the 40 or so pins that make up one of the huge connectors. Unfortunately the board later started acting up again, possibly because of my limited soldering skills, so I had to buy another board used.
 
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