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"K12S/KR" Technical Q&A K1200S/R Technical Questions/Answers

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Old 11-13-2012, 06:11 PM
rlecates2's Avatar
rlecates2 rlecates2 is offline
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K12R Driveshaft From K13R

Talked to a number of people, posted on several forums, and wasn't able to find a whole lot of information about the driveshaft differences between the K12 and K13. In hopes of finding a solution to the "CLUNK" when shifting gears (especially from N to 1st) someone suggested looking at the K13R driveshaft. My concerns go beyond just the feeling I'm hammering the transmission and everything else in the final drive every shift. I'm also concerned with longevity. I'm using my K12R for communting to the tune of approx. 20K miles / year. Since 7.4.12 when I brought her home and 11.4.12 I've put on over 6k miles. I really don't want to suffer the headache some have had with their final drive hub, nor the expense. So, if I can do something now to prevent such troubles later, then I feel that is money and time well invested. I'm close to having to replace the clutch, but after speaking with Marty Roach at length during the cycle show, there is another whole set of troubles to deal with. Which transmission shaft?... which basket?... and the clutch hub "may or may not fit" either way depending on if the clutch/hub shipped is new or old stock. So, seriously considering a slipper hub, barnett plates, and either a K1300 basket or possibly one machined of higher quality... but that's another story.

After some digging I was able to find that the K13 shaft is actually engineered with 2 stage damper system "to reduce the load change reactions that are created during acceleration and deceleration." Heres a clip from the BMW Training information bulletin released on 02/03/2009.

So... I first checked on a K13R shaft from MAXBMW. The mothership wants over $1000 for a driveshaft. WTF???? Seriously??? Who comes up with this? I went to ebay and found one available from a bike with just over 4K miles for $80. K13R shaft at the top... stock K12R shaft at the bottom.

Took some measurements and they are identical in length and spline. The U-joints on the K13R piece aren't nearly as 'floppy' as the stock I removed from my cycle. I expect that's mostly from the nearly 12K difference in miles.

Some additional pics...

It also appears the K13R shaft is serviceable in terms of the damper system. The stock shaft has a machined rolled edge that prevents any maintenance. The K13R has a large c-clip just under the sleeve edge. Maybe even tune-able? For less aggressive riding and more shock absorption perhaps softer polyurethane elements could be used? Just guessing here.

What came out of my K12R

The K13R shaft that went back in...

I've ridden for a few days now and have to say there is definately a noticeable difference. The best way I can describe it is that the shift before felt like a hammer strike... and now it's a much less subdued rubber mallet strike. This HAS to be better for the driveline... and even the transmission too. Also, the shifting seems better... not great... but better. I don't know if it has to do with how hard it was shifting in to the previous gear and required more force to shift to the next??? I'm sure RFW will have some explanation as to why that's a ludicrous idea... so I'm interested in hearing that.

But this isn't a perceived difference. If BMW saw a need to make this 'enhancement' to the K13R then there must have been issue with the previous arrangement. This also leads me to believe that's why there were a number of changes noted in the same Training Information Bulletin regarding the clutch:

"Clutch, Gearbox and Final drive: The clutch on the new K1300 models have ben upgraded with revised friction material and a stronger spring plate, however the effort to operate the clutch has been reduce by the use of a larger 34mm actuation piston in the slave cylinder.

The gearbox has been modified to provide smoother more precise shifting characteristics. The changes include having the gear dogs undercut, there by providing a greater surface area for engagement. The shift forks now use 3-points of contact compare to 2 that were used in the K 1200 models, and the gearshift lever now rides on a ball bearing."

So that's that for now. I'm going to continue to research options in regards to the clutch and all the components that make up such. BMW OEM clutch/hub for $700+ seems awfully steep. For a few hundred more STM has their slipper clutch hub available. I'm also speaking with a member from another forum who is already in talks with a machine shop to make a better basket. Don't know just yet which way to go so any input there would be appreciated. Some have suggested a K13 clutch replacement to include the hub/plates ($737), basket ($874), slave cylinder ($170), and oil pump sprocket ($103). Hell... at $1,884 for OEM parts to replace what BMW has essentially said was poor engineering on their part by producing the upgrades/enhancements... whatever you want to call it... why shouldn't I look at alternatives?

Anyway... I guess that's enough... for now.
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Old 11-14-2012, 10:47 PM
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Re: K12R Driveshaft From K13R

Glad it worked out!
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Old 01-01-2013, 06:03 PM
gimpy9195 gimpy9195 is offline
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Re: K12R Driveshaft From K13R

great write up and loved reading the research.
2013 K13S Silver Bullet
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Old 01-01-2013, 09:59 PM
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Re: K12R Driveshaft From K13R

Persistence pays off!
Ain't woke
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Old 10-22-2014, 06:09 PM
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Re: K12R Driveshaft From K13R

reviving this thread because this looks to be the answer I was searching for. Just ordered a K13S driveshaft on ebay. Any tips you can share on installing it, now that (I presume) you've completed the installation?
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Old 10-22-2014, 07:56 PM
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Re: K12R Driveshaft From K13R

Stig, since the OP Rich not post from 2013 would be convenient if you sent him a PM...
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Old 10-22-2014, 11:31 PM
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Beech Beech is offline
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Re: K12R Driveshaft From K13R

Easy to install, bike on center stand, remove paralever in back, lower final drive enough so the shaft slips off the final drive, pull the rubber boot up front back so you can see and put in a screwdriver to hold up the front spline while going back in now pull out the drive shaft from the tube. Reverse things to install but be sure to use some moly lube on all the splines front and back. Doing this job tomorrow on my bike as part of a two year maintenance cycle (re lube the splines).
Beech Arriba, Abajo, Al Centro, Adentro
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Old 03-28-2015, 10:48 PM
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Bill Curlee Bill Curlee is offline
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Re: K12R Driveshaft From K13R

Still looking for the K1300 driv shaft.

2002 K1200RS BURNED UP 08 Jul 13
2007 K1200R Purchased 11 Nov13
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Old 03-09-2017, 03:57 AM
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Re: K12R Driveshaft From K13R

Good thread and has helped validate this as a doable and worthwhile mod.

Thanks Beech. Paraphrasing..
  • Bike on center stand
  • Remove paralever in back.
  • Lower final drive enough so the shaft slips off the final drive.
  • Pull the rubber boot up front back so you can see.
  • Insert a screwdriver to hold up the front spline while going back in.
  • Remove the drive shaft from the tube.
  • Clean the splines and apply fresh moly.
  • Reinstallation is reverse.
Does anyone know yet if the 1300 shaft is serviceable in any way otherwise? There's that circlip that suggests it might be.

Combining this mod, a fuel controller (done) and the gearchange lever bearing mod, I'm hoping to gain some improvement in rideability.
Cheers, Steve

1982 R100RS.
2006 K1200R
Melbourne, Oz.
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Old 03-09-2017, 04:10 AM
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Re: K12R Driveshaft From K13R

I can proudly say...... Told you so!!

Happy days.
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Old 03-09-2017, 04:56 AM
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Re: K12R Driveshaft From K13R

No disbelief here Patrique. Just multipiont confirmation needed before spending the bux.

The models after 3/2006 seem to have some improvements added here and there, so worth being careful.
Cheers, Steve

1982 R100RS.
2006 K1200R
Melbourne, Oz.
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Old 03-30-2017, 07:03 PM
pgetty pgetty is offline
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Re: K12R Driveshaft From K13R

With stock K12S try to synchronize 2nd to 1st downshift at around 10mph...nothing helps from the start on these bikes, per dealer. Besides 1300 driveshaft I upgraded shifter, clutch, modified basket, and finally changed to 10-40W Amsoil. Reduced heavy jarring to a light clunk, but probably spent too much money for a $6,000 bike.
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