K12 clutch master for K13? - K-Bikes.com - Excellence in Motion
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post #1 of 12 (permalink) Old Dec 23rd, 2019, 7:53 pm Thread Starter
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K12 clutch master for K13?

Hello all:

As stated elsewhere my 2010 K1300GT with 30,000 miles (which may have a Barnett clutch if I believe the PO) makes an awful KLUNK going into first gear from neutral, warm or cold, unless already rolling.

There seem to be two schools of thought about the KLUNK. One school (John Sykes) holds the KLUNK results from inadequate oil clutch plate oiling and promotes mods to increase oil supply to the plates; the other holds that the plates are "stuck" together by the oil.

I don't like KLUNK so I start in first gear, and try with varying results to get into neutral as I roll to a stop. But I'd rather not sit there for a long red light with a deathgrip on the clutch lever. I may be doomed either way.

"I read on the internet" that the K12 clutch master has a larger diameter than that used on the K13. Other things being equal, a larger master cylinder would push more fluid down to the clutch slave, allowing for better clutch plate separation and hopefully less KLUNK. It will also increase the effort required to squeeze the lever to the bar; I'm willing to live with that if it cuts the KLUNK and/or makes finding neutral easier as I roll to a stop.

Has anyone tried fitting a K12 m/c on a K13, and if so how did it work?

Happy Holidays from (sometimes) sunny Honolulu, Hawaii!

Last edited by Honolulu; Dec 23rd, 2019 at 7:59 pm.
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post #2 of 12 (permalink) Old Dec 24th, 2019, 4:22 am
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As a new owner to slant 4’s I’m watching all these threads with much interest. I’ve had a 1200RS brick for nearly 18 years and the shifts, including into 1st are perfect. Totally silent. I am very keen to do whatever it takes to make the 1300 the same, but for now it’s starting in 1st to avoid the clunk. I was hoping the Barnett clutch pack was the answer but it seems this may not be the case. Surely there is enough historical evidence from other (Japanese) wet clutches to know whether the problem is too little or too much oil or simply not enough throw to seperate the plates properly. I like your thinking on the 1200 MC but would you also need the 1200 slave if that too is bigger (dunno) as your idea is to seperate the plates further. It’s all well and good to have a bigger MC that pushes more fluid but does it not need a slave with a bigger throw?

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Last edited by flyingkiwi; Dec 24th, 2019 at 4:29 am.
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post #3 of 12 (permalink) Old Dec 25th, 2019, 6:41 pm
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K12 clunks too. Try holding the lever in in N then count to 4, then change to 1st.
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post #4 of 12 (permalink) Old Dec 27th, 2019, 11:11 am
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https://theriderspace.com/forum/tech...ssues-resolved
Here are three relevant items for the K clutch. Many were lost with the failed IBmw.com loss.
First is a long talk on Youtube, second is the british fellow who does lots of clutches, not all bmw. The third is a poster who sent his clutch to England to the guy and his thoughts.
You can not completely discount the Barnett clutch pack as the poster who has a problem did not install it him self.

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post #5 of 12 (permalink) Old Dec 30th, 2019, 6:32 pm Thread Starter
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Thanks Beech. According to the dealer my 2010 K13GT has all the appropriate parts UNLESS the PO mucked with it to install the Barnett clutch.

That the separation between individual clutch plates is a fraction of a millimeter seems to offer that more push rod throw (a smaller diameter slave cylinder or larger master cylinder) might allow greater clutch plate separation, hence the inquiry about the supposedly smaller diameter K12 slave cylinder. It could work, if the plates actually separate. Since BMW didn't do that, maybe it's not the path to follow and there has to be a travel limit inherent to the K13 clutch pack but I don't know what it is.

I closely followed John Sykes' and Patrique Hofmann's clutch discussions on i-bmwr and as linked above. Both offer that insufficient oil between clutch plates causes the KLUNK.

Alternatively it was recently offered that the KLUNK is caused by too much oil between the plates, and viscous shear forces between plates do not allow them to rotate independently when shifting, and the solution was (partly and maybe only for the N-1 shift) to hold the clutch lever for several seconds prior to moving the shift lever. That certainly doesn't work for me!

I recently met a long-time BMW tech (a Kiwi, actually) who recommended to use 5W JASO-rated oil. That would seem plausible, agrees with BMW's revised oil recommendation and is the least expensive option at this point; I'll do that soon.

It's occurred to me during a moment of lucidity or idiocy (which, remains to be seen) that the witness marks on the clutch basket suggest the plates may wear into grooves which inhibit separation. No one has mentioned this yet so likely it's not an issue (?).

Last edited by Honolulu; Dec 30th, 2019 at 7:58 pm.
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post #6 of 12 (permalink) Old Dec 30th, 2019, 7:26 pm
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You should be using 5W40 oil.

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post #7 of 12 (permalink) Old Jan 1st, 2020, 3:27 am Thread Starter
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Roger that, will change oil to 5W-49 soon and see if it presents any differently. My expectation is that it won't, but that's the path of least cost and resistance.
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post #8 of 12 (permalink) Old Jan 1st, 2020, 5:54 pm
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Originally Posted by Honolulu View Post
It's occurred to me during a moment of lucidity or idiocy (which, remains to be seen) that the witness marks on the clutch basket suggest the plates may wear into grooves which inhibit separation. No one has mentioned this yet so likely it's not an issue (?).
This was an issue with my 1200S, the basket material was soft and was worn. This caused the plates to hang up, and was easily felt when starting in first with a bit of forward movement upon hitting the starter.

When I got in there the first friction plate was completely worn, but the others were fine.
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post #9 of 12 (permalink) Old Jan 2nd, 2020, 12:53 pm Thread Starter
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And so what did you do? BMW only sells the plates as a package, not inexpensively.
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post #10 of 12 (permalink) Old Jan 2nd, 2020, 11:31 pm
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Dressed the worn basket with a file to smooth, and installed the Barnett plates. There was some rattle in neutral since the basket was no longer as snug, but the Barnetts worked well.
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