Clutch cover screws - K-Bikes.com - Excellence in Motion
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post #1 of 11 (permalink) Old Dec 23rd, 2019, 10:52 pm Thread Starter
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Clutch cover screws

Slowly starting to learn my way around this bike and was curious to know if the aluminium clutch cover screws can be replaced with stainless and if so would the torque value remain the same. Why was aluminium used in the first place - was it for weight saving? I have read here (I think) of a member who replaced his with Ti but that is a little to spendy for me. F

2002 K1200RS Owned from new. Pacific Blue of course. Suspended on Ohlins. 183,000kmís
2016 K1300R Black, 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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post #2 of 11 (permalink) Old Dec 24th, 2019, 2:37 am
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The Aluminum screws have been replace by stainless steel, but record of that was probably lost when i-bmwr.org went down. Unless someone reads and re-posts their experience.

To what torque would an SS fastener be installed? You have to understand the function of torque in the original fasteners - it's to create a clamping force between the slave cylinder and engine case. The torque stretches the portion of the screw above that which is embedded. The clamp force depends on the torque value, cross sectional area (?) and the modulus of elasticity of the metal used, that is, how "stiff" it is in tension.

I'd expect stainless to be "stiffer" than aluminum though softer than steel, so that the aluminum fastener clamp value would be reached at a lower torque value if using stainless. The original fasteners had pretty light torque values, thus the stiffer stainless screws would have even smaller torque. If you calc this out (not saying I have) you may find yourself thinking that the torque value is barely over finger tight. Alleviate your concerns by using some thread locker, and if you rely on that product to keep the fastener from coming out, all the torque needs to do is keep the face of the slave cylinder snug enough against the case to that engine oil doesn't leak out.

We'd also love someone to take an old case and find out at what torque value a stainless screw will strip out. Any takers?
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post #3 of 11 (permalink) Old Dec 24th, 2019, 4:57 am Thread Starter
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Thanks for the reply Honolulu, and pretty much as I expected - a lower Nm given the softness of the aluminium over the stainless. However, the screws in mention are to attach the clutch cover to the engine, not the slave to the clutch cover. While the same math applies, Iím not a big believer in using loctite (other than internal engine parts) so will reduce the Nm by a small margin and see what happens. IMHO, the Nm is very low and most home torque wrenches are not professionally calibrated, (they can be a bit inaccurate to say the least) so even reducing the Nm to compensate for stainless is a stab in the dark to say the least.

2002 K1200RS Owned from new. Pacific Blue of course. Suspended on Ohlins. 183,000kmís
2016 K1300R Black, 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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post #4 of 11 (permalink) Old Jan 21st, 2020, 5:41 pm
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Aluminum and stainless steel can and do corrode when put together. The two differing metals set up a galvanic couple and corrode. Add in some moisture and the reaction happens faster. If you have a large catholic surface area, in this case aluminium, compared to the anodised surface, the stainless, it isnít so bad but seeing as how both surface areas are the same Iíd be going for the aluminium bolts.

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post #5 of 11 (permalink) Old Jan 21st, 2020, 11:58 pm
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Live large. Buy the OEM aluminum screws and follow the proper torque sequence. If you ever slide on the side you will be glad the aluminum screws are there as they get seriously scraped and sheared off. With steel you would damage the case threads possibly. I agree with you about not using Liquid thread fastener where it is not called for. If all torqued properly they will cause no problems. The stretch will take care of any possible flex, there are plenty of them. Besides, Red loctite 262 drys harder than aluminum and seriously mess with the female threading. Not saying you would use anything but blue 242 in aluminum. With the 90* turning in the procedure it is easy to come to the correct force on these bolts. Put the gasket on dry. If the original aluminum/silicone gasket is not bent I have reused them but the paper one seals just fine also.

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post #6 of 11 (permalink) Old Jan 22nd, 2020, 5:20 am Thread Starter
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Sure I hear you Beech and I respect your opinion, but are you telling me that the many owners who are regularly pulling their clutches to check wear and oil feed to the plates etc in pursuit of a fix are replacing the aluminium screws every time?

2002 K1200RS Owned from new. Pacific Blue of course. Suspended on Ohlins. 183,000kmís
2016 K1300R Black, 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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post #7 of 11 (permalink) Old Jan 22nd, 2020, 1:03 pm
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Well let's think about this. Unless you are going to take things apart and make changes to the K12 thrust shaft or drill holes in your basket no one is going to pull the cover and go yup, there is oil in there it must be flowing. A wear check happens when there are symptoms. Not often. I hate to toss this out, but, the engineers who put this thing together gave it some thought. They still use this system 15 years later (now) on bikes. I just wish someone would find a source for bulk purchase of 6M aluminum torx screws. Buy them by the box if you're into your bike every year or less. Your idea of a wear check has merit as you can clean between the pads of that last plate next to the basket thrust face. This build up is one cause of slipping and cutting into the aluminum pressure face there. Even that only needs to be done every few years. I had a master BMW tech tell me they expect a K bike clutch to last 35,000 miles. After that it was up to whatever. I got 112,000 out of mine and it had 20k more to go no problem, but would have benefited from a cleaning. I do mostly highway miles. A set of screws costs about 35$ US. Pesky but not even as much a the oil for a change. I think the gasket is about 42$ so that is the killer part with screws only 1.50$ each. I suspect bulk they would be less than 50 cents though. Next to K1200LT bikes this series K bike is the most expensive BMW to maintain. (well maybe the K1600 now). Not a cheap hobby. Keep in mind the hundreds of dollars you save whenever you do your own work.

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post #8 of 11 (permalink) Old Jan 22nd, 2020, 3:41 pm Thread Starter
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You put forward a compelling argument Beech, and I think the way to go is finding a better source of aluminium screws than the local BMW stealer. My 1300R is one of the last made with less than 6000kms on it, however I believe that as it has sat for extended periods the bottom plates are likely gummed up and would benefit from a good clean and inspection. Then there is the possibility I will swap out the pack for a Barnett set, possibly with an extra plate, machined down 50%. Currently the bike slams into 1st, regardless of how long I pull the clutch prior to engaging. Yes, I start in first, and stay in gear at lights etc, to avoid the damage but it still pisses me that this problem exists.
I want to clean and inspect the plates with a fresh oil change and ride it to see if that helps. Then I might want to go in again to change the pack. I spoke to another 1300 rider recently who said his bike is fine and engages 1st nicely although I have not witnessed this.

2002 K1200RS Owned from new. Pacific Blue of course. Suspended on Ohlins. 183,000kmís
2016 K1300R Black, 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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post #9 of 11 (permalink) Old Jan 22nd, 2020, 9:52 pm
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Okay here you go...

The four screws for the clutch slave are listed on realoem.com as 11147678478, ISA screw, M6X20. The screws holding the side cover to the engine case are seventeen 11137676132, ISA screw, M6X25 and three 11147678478, M6X20 which also hold the heat shield, for a total of 20 fasteners.

Grainger.com shows item 36RH95, A2 stainless (alloy type 304) M6x20, hex head, DIN 933, $25.37 for a pack of 50 (51 cents each), and item #6BB27, A2 stainless M6x25, hex head, DIN 933, $16.91 for a pack of 50 (34 cents each). Odd that a longer screw is cheaper...?

But a pack of 50 is only enough for two bikes. Want larger quantities, go to (for instance, no affiliation) fastenersuperstore where item 549597 is a carton of 2,000 M6-1.0 x 25 mm Machine Screws Torxģ Button Head 18-8 (A2) Stainless Steel screws will cost $206.28 or a measly 10.3 cents apiece. Note that 18-8 stainless is the same as Type 304.

Such costs illustrate what we already know: BMW parts prices are f'n outofthisworld, even for common industrial fasteners (Al vs SS aside).

Now if you're Down Under, shipping becomes an issue and another net search is in order.

Last edited by Honolulu; Jan 22nd, 2020 at 9:58 pm.
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post #10 of 11 (permalink) Old Jan 23rd, 2020, 4:44 am Thread Starter
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Thanks Honolulu, freight down here will be a deal breaker but I sure appreciate the time you put into sourcing screws for me. I sat down this evening to search aluminium screws and came up with Probolt, an international company with outlets in Australia. Sure there is Fleabay and Alibaba etc peddling their Chinese wares, but Probolt sell British made screws at a comparatively reasonable price. 1.78 (USD1.23) each including taxes is probably good buying here for aluminium. That works out at about 43.00 (USD30.00) for a set including the four slave screws. Think Iíll place an order for a set.

2002 K1200RS Owned from new. Pacific Blue of course. Suspended on Ohlins. 183,000kmís
2016 K1300R Black, 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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