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78 r80/7 drive shaft bolts wrench

yankeeone

New member
Hi a few years ago I rehabbed a 86 r80, I am now doing a 78, when I did the drive shaft bolts last time I made the wrench and torqued them down , now I cant remember what to set the torque wrench to with the added length of the little wrench ala snowbaulm.Anyone know?
 
Hi a few years ago I rehabbed a 86 r80, I am now doing a 78, when I did the drive shaft bolts last time I made the wrench and torqued them down , now I cant remember what to set the torque wrench to with the added length of the little wrench ala snowbaulm.Anyone know?

You need a 10mm 12pt wrench on one end that will fit your torque wrench on the other end. Attach the wrench so it is at a 90 degree angle to the handle of the torque wrench, thus minimally lengthioning the effective torque arm. Then use the specified torque for the bolts.
 
I think Snowbum has a section on special tools.

Also, check this: http://www.northwoodsairheads.com/Tools.html

About half way down the page, there is a pic of what you want to buy or make.

*************************
If you don't have one of the special tools, you can make one; buy something that works......or, use the 10/12 mm dual box-end wrench in the standard BMW tool kit, and give the wrench what we call a 'good grunt'. That Good Grunt works fine with the stock length 10mm/12mm dual box end wrench.
Some have used that wrench and a 3/8" square drive torque wrench, calculating the lowering of the setting due to the wrench length. I have that calculation method in my torque wrench articles.
The torque you want on the bolts is 29 footpounds, if using a torque measurement. If your bolts came with split lockwashers, remove them, do NOT! reuse them, do NOT replace them. Get the new SHORTER bolts. HEED MY WORDS!!
Put ONE small drop of Loctite BLUE on the clean threads before torquing.
The original factory tool is pictured in my tools article. It is nothing more than a square drive of a socket with an added slit, to which a 10 mm offset box portion (they cut the other end off!) was brazed or welded (have seen them pressed too) into the square drive slit.
Three photos of the factory tool are located, and described, etc., in section 4 of my tools article...that means it is about 2/3 of the way down the tools article page.
The article is number 65 on my website.
http://bmwmotorcycletech.info/tools.htm
snowbum
 
Thanks for the help, on the last bike I rehabbed, I made a copy the factory wrench, I just couldn't remember the calculations for torque, when I checked the last bike 86 r80, the bolts were loose, and I replaced them, on this bike I put the wrench to them and they are tight, so I am going to leave them.
The Max BMW parts shows the long bolts with washers, have they changed there minds? The bike has 65 thou on it so it should be ok?
 
Thanks for the help, on the last bike I rehabbed, I made a copy the factory wrench, I just couldn't remember the calculations for torque, when I checked the last bike 86 r80, the bolts were loose, and I replaced them, on this bike I put the wrench to them and they are tight, so I am going to leave them.
The Max BMW parts shows the long bolts with washers, have they changed there minds? The bike has 65 thou on it so it should be ok?

Max (Rusty) encouraged me to purchase the shorter bolts without washers, and as Snowbum suggested, DO NOT use the washers. Apparently they can break, and when that happens, the bolt goes loose. I actually had that happen on my R50/2 when I was on a trip. Happened exactly in front of the US Capitol building. I managed to nurse the bike over into the middle park, and practically tore the whole back end off to fix, right there on a 100 Deg. day. Got the new bolts up the road (had a friend on a Moto guzzi go get them for me) and installed by 2:00 PM that day. Got home back to NE Ohio that evening!

Also, I was told that the torque wrench routine was not really necessary. Snowbum's "good grunt" would work fine with blue Loctite.
 
Also, I was told that the torque wrench routine was not really necessary. Snowbum's "good grunt" would work fine with blue Loctite.

Torque wrenches are never "necessary" if you have a well calibrated grunt. If peoples' grunts were generally well calibrated, you would not find so many stripped out threads on motorcycles. Lots of untrained wrenchers tighten it "all the way plus a quarter-turn". Tell a seasoned M/C mechanic, a retired librarian, and a pro football player working on his first motorcycle to give it "a good grunt". Tabulate removal torque. Give each a torque wrench and a spec. Repeat and compare. Providing torque specs (either force or angular) is the only reliable way that a technical writer can communicate how tight a fastener is supposed to be. Sure, torque specs in manuals can be wrong and they should be tested against reality and a "common torque" chart. Conversions (torques listed both in N-m and ft.-lbs.) are always suspect for conversion errors. I normally use the writer's native dimensions or check the math.

I have done driveshaft bolts by feel as well when I had to (or didn't know better) and never had one let go. However, with fasteners this critical I choose to use the tool and the spec whenever possible. It is my observation that seasoned mechanics use torque wrenches more often than rank amateurs. As I have gained experience, I find myself using them more often rather than less. Certainly I have a better calibrated "grunt" than I used to have, but I also have more knowledge, judgement, technical literature, and tools.
 
Torque wrenches are never "necessary" if you have a well calibrated grunt. If peoples' grunts were generally well calibrated, you would not find so many stripped out threads on motorcycles. ..........
I think this is where a lot of us rural mechanics get in trouble as metric threads are generally much finer than our past experience with US Coarse threads. We get by with metric threads into steel, but fine threads into softer materials seem to generate a lot of forum thread-strip questions.
 
I ordered new short bolts, when I put the rear drive back on , do I just use dry gasket?

Where are you talking about using dry gasket? On the driveshaft boot? I can't think of anywhere else to use any gasket type material. I must be missing something here. Personally, on the driveshaft boot, I would use a real thin film of black silicon sealer available from any auto parts store.

On the bolts, per above, use blue Loctite to secure them. Make sure they are first clean and free from oil.
 
I, too, was confused about sealant, but he did say his "rear drive", so this must have been more than just the four bolts at the back of the transmission. There are four bolts where the rear drive bolts on...hmmmm....
 
Clarify -- the new bolts will go on the drive shaft to transmission , inside of the rubber boot. The gasket is where the rear drive bolts to the swing arm.
 
Clarify -- the new bolts will go on the drive shaft to transmission , inside of the rubber boot. The gasket is where the rear drive bolts to the swing arm.

Ok! Gotcha. I did't know that you had removed the rear drive to do this.

I may get some flak for this, but I would use a very thin film of silicon seal on the swingarm-to-rear drive gasket as well. I have seen that stuff seal water pumps in cars with NO gaskets. It was especially developed for metal to metal seal with no gaskets to take up space. When properly installed, the silicon material will work wonders!
 
Rear drive gasket

There is no requirement for sealant on this gasket and I can understand why. The rear drive has to be connected to the swing arm so that, when the axle is inserted, it slides in with a minimum amount of friction.
The correct way to align everything is to bolt up the rear drive without tightening the nuts. Then you insert the axle. This aligns the drive unit so that the axle slides in smoothly. Then you tighten the nuts. So if you add sealant then you're pushing the drive unit towards the rear, thus screwing up the alignment on a different plane. Believe me when I say that I've seen some shade tree mechanics put globs of silicon seal on the gasket to the point that you have to drive out the axle with a hammer! This leads me to the rule of thumb, that if you ever work on a bike that has red, high temp silicon seal oozing out of every mating surface, then you know that someone who doesn't know squat about mechanics has been working on the bike.
 
There is no requirement for sealant on this gasket and I can understand why. The rear drive has to be connected to the swing arm so that, when the axle is inserted, it slides in with a minimum amount of friction.
The correct way to align everything is to bolt up the rear drive without tightening the nuts. Then you insert the axle. This aligns the drive unit so that the axle slides in smoothly. Then you tighten the nuts. So if you add sealant then you're pushing the drive unit towards the rear, thus screwing up the alignment on a different plane. Believe me when I say that I've seen some shade tree mechanics put globs of silicon seal on the gasket to the point that you have to drive out the axle with a hammer! This leads me to the rule of thumb, that if you ever work on a bike that has red, high temp silicon seal oozing out of every mating surface, then you know that someone who doesn't know squat about mechanics has been working on the bike.

The whole purpose of a gasket to begin with is to compensate for two mating surfaces that are not perfectly matched, due to machining imperfections. Also, over the 35+ years, I am sure that the gasket material hasn't been perfect either, and had a "tolerance" as to its thickness and compressabiity.

When properly used, the silicon sealer would at most add a thickness of .0005 (probably not even that as it would fill gaps, and squeeze out everywhere else which wouldn't affect alignment at all. I am sure the "tolerances" on the swingarm and on the rear drive machining wasn't that close. Add in the gasket material, and the tolerance "stack" becomes more. Silicon will not affect this at all. When used properly, there would be very little squeezed out, and that would be nearly imperceptible, if at all.

Also, considering the fact that the other side of the swingarm is a squeeze bolt I can guarantee that if you ever had a problem inserting an axle, it wasn't because of .0005 thick of silicon.
 
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