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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: rbm on January 09, 2016, 10:04:21 PM
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Helping a friend today to do maintenance on his '84 K100. The bike has probably been an RT with crashbars in a previous life; it's now naked. The frame is attached to the block at the front using crashbar bolts. These are #6 and #7 in the diagram below:
(http://www.realoem.com/bmw/images/diag_4c7.png)
What socket type and size loosens/tightens these bolts. It is not hex. It appears to be double-square.
Any good McGiver suggestions for torquing if the correct tool is not to hand??
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They are probably Torquez sockets you can get a starter set pretty cheaply from any good auto store, keep the receipt in case I'm wrong. I thought I was wrong once but I was mistaken. :clap:
Regards Martin.
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Any good McGiver suggestions for torquing if the correct tool is not to hand??
Bolt & nut in place of part #8 ... ?
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I'm not familiar with that part, but from the diagram it appears to receive a threaded insert.
If you get some threaded rod or a same-size bolt and a few nuts you may be able to lock some nuts onto the stud and turn the part in question. You may be able to use a torque wrench for that - but then you will need to release the nuts and stud without moving the part. See below...
Is there room to get a vise-grip on it? Sometimes you can wrap a part of an old inner tube and get enough pressure with the vise grips to turn it without damaging the surface - or hold it still while you extract something from it.
That's all the MacGyver I've got in me today...
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Had a look at my Torquez sockets they are 6 sided, I would go with Scuds suggestion threaded rod and two nuts. Screw in the rod then screw on the two nuts and tighten first nut down onto the bolt. Then while holding a spanner on the first nut tighten the second nut down onto the first. You then undo using the first nut. Failing that it should be possible to get an eccentric stud extractor onto the head of the bolt.
Regards Martin
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Just tried my eccentric stud remover on the same bolt on my 75s and there is just enough room for it to work. the bolt on the 75s is just a smooth allen bolt and it gets a grip on it. So your bolt should be no problem, if you are not going to remount the crash bars I would replace with normal allen bolts. Picture of stud remover attached.
Regards Martin
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FYI, my 250SGS has metric square head bolts on the cylinder head. Sears has metric 8-point sockets, but I'm not remembering what sizes. IIRC, not too far from you?
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When I put the crash bars on my RT I used a 12 point 1/2" drive socket. 7/8" fits a bit loose, but works. I am guessing the correct metric size is 22mm.
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I just did an Internet search for "double square socket" and there look to be plenty of options.
Have you seen "The Google"? :hehehe
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I don't understand the double square. My bolts have 12 point heads, probably 22mm. Are there two different heads available for these bolts?
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Thanks for all the suggestions and information.
In Canada, we don't have as much choice as in the US. If I searched, I probably could find a local supplier for these special tools.
Our constraints are weather and good will. At the moment, winter up here has abated but I'm not too sure how long that will last so I want to get this service finished before the temperature drops too much.Also, my friend has the bike is on my lift in his friend's garage so there might be urgency to get this job over with soon. It's not my bike so my friend needs to work that out with his buddy.
I'll try out the 22mm-7/8" 12-point socket idea.
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Photos of bolt and standard 7/8" 1/2" drive socket. I have inserted the bolt through the socket's square drive hole to better show the fit of the head points in the socket.
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FYI, my 250SGS has metric square head bolts on the cylinder head. Sears has metric 8-point sockets, but I'm not remembering what sizes. IIRC, not too far from you?
Square head bolts are what 12 point sockets were originally designed for. Square heads with four points engage every third point in a 12 point socket while hex head bolts engage every second point in a 12 point socket. A 12 point socket is sort of a "universal" pattern that works with hex and square head bolts. The downside is that they can't transfer as much torque as a six point socket. That is why impact driver sockets are always 6 point.
These 8 point sockets look to be generic Torx sockets, and won't work because of different geometry of the points, not to mention the wrong number of points.
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Clear explanation and useful photos, Gryph. :2thumbup:
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Cheers Jim. Thank you for the excellent explanation.
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My pleasure, Rob! BTW, think there might be any interest in getting the Motobrickers from the GTA together for lunch some time this winter? Might be fun to share what we're up to with our winter projects.
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BTW, think there might be any interest in getting the Motobrickers from the GTA together for lunch some time this winter?
My shop is always available for after lunch chews. There's a good F&C place close by.