BMW K bikes (Bricks)

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1Back to top Go down   Why one-time use bolts on clutch? Empty Why one-time use bolts on clutch? on Fri Aug 16, 2013 5:02 pm

jjefferies

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I've been searching for the logic behind the one time use only policy on the clutch bolts. Best answer for one time use only any bolt that I've found is from a (Gasp) Harley forum
. The correct term for so-called stretch bolts is "torque-to-yield" bolts. The rotor bolts on my bike have six radial lines indicating that the bolt is a grade 8. A grade 8 bolt that has been properly torqued (never over-torqued) may be used over and over provided it hasn't encountered any fatigue damage, or otherwise obvious visual damage.
....
Any bolt that has a direct torque specification of so many inch pounds or foot pounds is not a torque-to-yield bolt. Torque-to-yield bolts will always have a torque specification of a relatively low torque value followed by some number of degrees of additional rotation. Once a torque-to-yield bolt has been tightened past its elastic deformation state (usually at or near the initial torque value) it should not be reused. This is because the bolt has been permanently deformed once it is torqued beyond its elastic limits.

A standard grade 8 bolt is never torqued beyond its elastic limits in normal use.
But are my K75 clutch bolts "torque to yield" as described above or is there some other mysterious BMW rationale? Curious minds and all. I'm off to buy more bolts.

    

2Back to top Go down   Why one-time use bolts on clutch? Empty They are not on Fri Aug 16, 2013 6:03 pm

ibjman

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They are not torque to yield, but they are known to be "fragile" & subject to breaking off.

Please note that they need new washers as well.

Last, be very careful in torqueing these. Only go to the bottom end figure of the torque spec-----(not just a little more) some have been known to break even at the low spec. These aren't known to come loose either, so the lowest allowable torque is the best plan.
 I'm not sure about buying "generic" bolts at the local store. The OEM ones certainly are not a deal breaker cost wise. Also, I think the BMW washers are special in some way, but I'm not certain.
Regards, Ibj...

    

3Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Fri Aug 16, 2013 8:25 pm

RicK G

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I get rid of those stretch bolts as soon as they come out either in one piece or bits with the head drilled off.
My opinion is that they are not needed in that situation and I use a bolt that I managed to source but I need to cut them down by 8mm. They are a metric 8.8 which is the equivilant to a grade 5 and have a hex head not that rediculous shallow socket head which rounds out as soon as it sees the allen key.
I have had no problems at all with them and I can use them over and over if the need arises.
I also know of a few people who are BMW trained and either use the OEM bolts again or the hex bolts I use and AFAIK none have had problems with breakages.
My honest opinion is that they are designed to get money from the people who let the BMW stealers neglect and abuse their bikes while performing services "by the book" Ha Ha!
Yes I am cynical but if there is one thing I have learned over the years is that I have not been anywhere cynical enough.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

4Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Fri Aug 16, 2013 8:44 pm

jjefferies

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Ah well, Interesting. Just got back from Bowlin's, specialist in fasteners bowlinbolts.com, over in Berkeley. Learned a bit. Seems that 7,9, 11 mm bolts are the bad boys of the fastener industry. They're the oddballs and outside of OEM suppliers come in only the simplist heads/shapes. And reputedly are  fav's mostly with the automotive industry in speciality applications (like the clutch on K bikes). I took a sample bolt off my bike and they were able to match it exactly only to a hex head. Seems the BMW bolt is a std 8.8 not one of the torque and stretch variety cited above but with the allen head. At $.50 each I got six hex heads and checked them out on the clutch when I got home. See no reason why they won't work. Plain old socket fits over them perfectly and they don't stick up any more than the BMW allen head variety. And I can use the BMW washers as well.As an aside, I checked the 35lb pile of BMW bolts that my friend gifted me and couldn't find any other 7mm bolts.

Now here's another odd question. The bolts (BMW and the new 8.8 hex heads) are steel. They screw into an aluminum clutch housing. But I've not seen any warnings to use an anti-seizing compound when putting them in. Did I just miss that or is there a reason they wouldn't want to use an anti-seizing compound?

thanks guys.

    

5Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Fri Aug 16, 2013 8:59 pm

RicK G

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I use the loctite anitsieze on all the steel bolts that go into alloy, seems to cover almost all the bolts on a K, and use shake proof washers like the OEM (1/4 in do the job they usually leave enough clearance to go on a 7mm bolt).
I don't understand why the shallow head bolts as there is plenty of room for the normal depth head.
I am glad that a bolt specialist has said to you that they are a normak grade 5 bolt as I always suspected they were and I also have a friend here that is very knolledgable on bolts and he has experssed the same opinion.
The head bolts are the stretch variety and I fully intend to replace them with grade 8 full depth socket head bolts when I have the head of next time and that isnt far down the road as the little darling is using oil now.
The bike has been badly neglected as the major dealer in Sydney did all the work on it for the last 100,000km.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

6Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 3:58 am

Guest

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The local BM shop says that BMW told them the black coating on the bolts is some sort of torque assist coating and is stripped from the bolts when they are removed. He also says he just uses the old bolts Smile

The head bolts in my R1100 are torque to yeild. You do them up to X Ft Lbs and then an additional 90 degree turn. It is done as part of the first service for the bike and if they are replaced I guess.

    

7Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 5:36 am

MikeP

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Any time they're disturbed, such as re-setting the end float of the rocker shafts - worth doing when the valves are adjusted once it's done a few miles.

    

8Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 6:12 am

charlie99

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rick and I discussed this when pulling  some engines apart recently

I guess its the old, "keep the customer coming back "....with exclusive product and installation instructions ...
worthy to scare off the amateur sufficiently from doing his own work . value added work tasks ...? I suggest so ...a good doctrine to establish and practice ...erm for the bmw dealer .

I see no reason why standard bolts could not be used on that clutch basket  ...its not like its under extreme stress or anything ...all that stuff is done on the spring and friction plates huh ?


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OWhy one-time use bolts on clutch? Au-log10

"redframe" rs "bitsa"  with many contributions from the k100 community ,,with many thanks
    

9Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 6:30 am

MikeP

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@charlie99 wrote: ...its not like its under extreme stress or anything ...all that stuff is done on the spring and friction plates huh ?
Seriously?

    

10Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 6:39 am

charlie99

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well it does already have locating pins etc ...so its just holding the change in mass- revs  (as gear changes are happening ) by sheer strength is it not ? I recon 6 x 7 mm bolts would be admirably suitable and probably over designed.

cant think of ANYBODY ever experiencing a failure in that region EVER .... more likely stripping the heads rather than anything else .
there are millions of vws on the planet with similar setup ...and they don't fail ...period .


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OWhy one-time use bolts on clutch? Au-log10

"redframe" rs "bitsa"  with many contributions from the k100 community ,,with many thanks
    

11Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 7:29 am

RicK G

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This is always going to be a contentous issue but I firmly believe that "if" the clutch bolts are what BMW claim then there is no purpose served by using those type of bolt there.
I would not recommend grade 8 (10.10) because they are not as strong laterally as the grade 5 (8.Cool.
The locating dowels are hardened steel and between them and 6 x 7mm grade 5 bolts there is no way that they would sheer and they are quite strong enough to hold the plates together. I have yet to hear a satisfactory explanation as to why BMW ever used them.
The head bolts are a different game. Robin I don't want you to take this personally but if the head bolts are to be replaced and not retensioned why do they not replace them at the first service rather than just retorque them.
I have seen the stretch bolts let go when reused on a 6 cylinder ford engine but they take a hell of a stretch, 35ft/lb then 270° rotation. Both times they have let go was some time down the track, around 30 000km.

Next time I do a cylinder head on a K I intend to get grade 8 bolts from the bolt shop and pull them down to 60ft/lb and retension at 1000km.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

12Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 7:35 am

MikeP

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@RicK G wrote: Robin I don't want you to take this personally but if the head bolts are to be replaced and not retensioned why do they not replace them at the first service rather than just retorque them.
The R11XX head studs don't have to be replaced each time they are disturbed, just torqued and slackened, then turned by the required degree.

    

13Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 7:52 am

RicK G

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Yeah thats fair enough Mike I was going on what Robin was saying and he was going on what he was told.
I consider that the object of taking the bolts to a small tension then x deg turn takes the head gasget to the required thickness to work correctly rather that a higher torque setting which depending on who and how that could vary widely.
When I was doing my fitting apprenticeship and thats a long time now we were shown how lubricating the thread and even under the bolt head would change the actual pressure holding the 2 surfaces together.
Dry thread on a 1/2 UNF bolt at 60ft/lb was about 1 ton then using neversieze it went to 4 ton then under the head went to near 5 ton but very rarely do you see a manual tell to lube the threads before you tension.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

14Back to top Go down   Why one-time use bolts on clutch? Empty Re: Why one-time use bolts on clutch? on Sat Aug 17, 2013 8:07 am

Guest

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@RicK G wrote:Robin I don't want you to take this personally but if the head bolts are to be replaced and not retensioned why do they not replace them at the first service rather than just retorque them.
That's just what I got from the BMW manual I downloaded thanks to Klompy's 'Need a Manual' Thread and a Chris Harris utube video on doing heads on an oil head Smile

I ordered a Haynes manual from the UK but ebay closed that sale and advised people not to send funds. Too late for me, already sent $60 but will wait to see if a manual arrives before taking action with paypal late next week. What a hassle Sad  Should have just suck to motorworks/bins/etc.

    

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