Airhead "Tips and Tricks"

[Plaka]

Originally Posted by Les_Garten

How often do you have to un-button the driveshaft?

It's a cost versus benefit analysis

or

cost versus risk analysis

It's it's $6 versus catastrophe and you do it every 10-20 years I'm not sure I appreciate the argument for re-using the old bolts.

One of the risks of these bolts letting go has to be death as well. I never tempt fate with Clutch Bolts or flywheel bolts either.

I'd say every 3 years is good and if you can go longer, then better. The wear item is the boot rather than the tranny or driveshaft. You disconnect the driveshaft to put in the new boot. A cracked boot is bad news because it admits water to the shaft which mixes with the oil and makes a mess of the bearings. This is one area I like to leave kinda dusty and greasy. Keeps the UV off (we got ferocious UV around here). if it does get cleaned I soak it down with that 300 stuff so it gets back to dusty and greasy pretty quickly.

[Plaka]

Originally Posted by supershaft

In my experience, the bottom line is that IF those bolts are properly torqued, new or good used, it makes no difference, those bolts do not need loctite. They never come loose if they are properly torqued with no loctite. They don't need to be periodically checked IF they are properly torqued. If they are in good shape, they don't need to be replaced.

Cost versus risk analysis? There is virtually no risk in my experience IF they are properly torqued. It makes no difference if the bolt is used or not as long as it is in good shape. A new bolt might be a bad one? Maybe the risk is less with used and tested bolts? Personally, I wouldn't worry about it that much. As a professional BMW motorcycle mechanic and almost life time airhead rider, I have literally hundreds and hundreds of drive shaft bolt installations under my belt. As far as I know I have never had one come loose and I never use loctite. I never check them. I torqued down the used bolts holding my driveshaft on right now around 70,000 miles ago. No loctite and I am not going to 'check' them. "Checking" them is for people that didn't torque them down right to start with. Same with using loctite IMO. NO need for it if the job is done right. I have seen a lot of drivehaft bolts come loose but all them were not tightened enough. Maybe a few too much? End of story IMO.

The engineering of the joint is a particular torque applied to a particular bolt that is intended to distort and provide a locking action. The bolts are not re-used because they can only meet the specification once.

You can deny any bit of engineering on the machine that you want. You say you have had no problems. great, you have one data point. The people that engineered that joint have thousands of data points and more testing than you will ever do riding. personally I'm going to go with what they came up with. I know they've changed the joint and I also know they didn't do it for production economy reasons---they had a problem. it wasn't a big enough proplem to do a recall, but they did spec the newer bolts for service on the older machines. The torque specs have a tolerance. From the factory, some bolters fer at one end of the tolerance, some at the other. The variation tends to be sinusoidal. it may be that only fasteners at one extreme of the tolerance had problems. on solution is to tighten the tolerance. But this is costly. Another is to change the fastening system to be more reliable across the tolerance range. I suspect this is what they did. The fastener will distort enough throughout the tolerance range to give acceptable locking.

You can set up one bike and reuse your fasteners and have absolutely no problems. You can also buy one lottery ticket and win the lottery. it's a statistical game either way and you really don't know what the statistics are. BMW does know. If there is a problem they hear about it.

BTW, you mention you have seen a lot of drive shaft bolts come loose because they weren't tightened enough. Were you there when they were tightened? How do you know they weren't tightened enough? (aside from simply assuming it---ie, some seriously circular logic). What is inarguable is that you have seen loose drive shaft bolts. (I ain't gonna call you a liar). it could very well be that they were tightened just fine...but they were re-used. Do you really know the history that caused the problem?

You can say you are a professional mechanic but if you don't follow a spec on something like this you aren't one I would patronize. You might be re-using conrod bolts too. if I want an engineer I hire one. i expect a mechanic to be exactly that even though many (like many machinists) feel they need to play engineer for...I dunno what? Status? In my experience both machinists and mechanics often know things the engineers don't simply because a lot of engineers are clueless about either discipline. But it cuts both ways and when things go wrong it isn't because engineers are trying to be machinists or mechanics.

There are a number of critical fasteners on my bike I have Re-engineered. I changed the material to stainless. It has less strength than 8.8 and has a habit of galling so it usually gets antisieze. My brake caliper bolts are an example. These suckers come in and out every time I take a wheel off. I decrease the torque because of the lubrication and check them a lot. I'm taking the risk on myself. So far they have not loosened between checks. When tight they are in pure shear and a pair of them is plenty for the forces the brake pots can exert. So I don't worry---but they are right out in the breeze and easy to check.

[Beemerboff]

http://ken-co.com/permatex/threadlock-blue.pdf

This data sheet confirms no torque compensation is required with this product, but Loctite make a huge range of products and the assumption I made that no compensation is needed with any product in any every application is probably much harder to prove, and more than likely incorrect.


But generally on a motorcycle forum we are discussing medium/high strength fasteners in a limited range of sizes, and a limited range of thread locking products.

And the statement seems to hold in these circumstances.

We are often given a torque range of around +- 5%, so if you have any concerns it would seem prudent to go for the bottom end of the recommended scale, or if you have only a single figure just leave the torque 5% under, but with the factor of safety commonly used with mass produced fasteners in non critical situations it isnt going to make a lot of difference if you dont.

But, as Henkel said, if you want to change things with the flywheel or conrod bolts just make certain you know what you are doing.

The last two sets of drive shaft bolts I bought came with a hard red compound on the threads, so if you are buying current factory stock you are going to have to clean it off if you dont want locking compound.

[Plaka]

Originally Posted by Beemerboff

http://ken-co.com/permatex/threadlock-blue.pdf

Originally Posted by Beemerboff

This data sheet confirms no torque compensation is required with this product, but Loctite make a huge range of products and the assumption I made that no compensation is needed with any product in any every application is probably much harder to prove, and more than likely incorrect.


But generally on a motorcycle forum we are discussing medium/high strength fasteners in a limited range of sizes, and a limited range of thread locking products.

And the statement seems to hold in these circumstances.

We are often given a torque range of around +- 5%, so if you have any concerns it would seem prudent to go for the bottom end of the recommended scale, or if you have only a single figure just leave the torque 5% under, but with the factor of safety commonly used with mass produced fasteners in non critical situations it isnt going to make a lot of difference if you dont.

But, as Henkel said, if you want to change things with the flywheel or conrod bolts just make certain you know what you are doing.

The last two sets of drive shaft bolts I bought came with a hard red compound on the threads, so if you are buying current factory stock you are going to have to clean it off if you dont want locking compound.

I would imagine we are spitting hares and the torque difference lies within the tolerance range as you suggest.

The four new bolts I have are clean and dry but I bought them about 3 years ago from Capitol Cycle (USA).

It could be that the newer bolts have threadlocker (or a calibrated lubricant) because of some requirement of the newer bikes. If it does no harm on the older bikes then the older part will be dropped in favor of the newer. Less parts to stock and they won't change the part number. Or it could be an ongoing effort to address an old problem. I'm not in a loop to know if a service bulletin has been released on it. (although I could make some inquiries and in light of what you just said, probably will). Certainly wouldn't hurt anything to install the new ones I have dry per spec and then hit them with some green locktight.

The only places I find (on an airhead) where the torque values change in a big way, and were the greatest care must be taken with threadlockers, is on just about any steel insert in a plastic part. On both my instrument pod and fairing there are cracks around the steel inserts. I patch them as best possible with epoxy and the like but those inserts are just begging to strip out of the plastic. So the bolts run into them get tightened most very gently and I use the very low strenth locktite to keep them from loosening. I use some silicone dielectric grease on the instrument pod gasket because I'm not really tightening the screws enough anymore to get proper gasket compression. The grease keeps water out. Those pods are unholy expensive and I've used up most of the plastic magic I know to reinforce the cracks around the inserts.

I do BTW re-use some of the one-shot bolts for other things. Those conrod bolts are very nice for bracketry and whatnot. I'm working on some mirror brackets and I'm going to try to incorporate a pair, mostly because they look cool and I need a bolt that initially clamps and then get's it head and nut ground off leaving behind a brazed in post.

[supershaft]

Originally Posted by Plaka

The engineering of the joint is a particular torque applied to a particular bolt that is intended to distort and provide a locking action. The bolts are not re-used because they can only meet the specification once.

You can deny any bit of engineering on the machine that you want. You say you have had no problems. great, you have one data point. The people that engineered that joint have thousands of data points and more testing than you will ever do riding. personally I'm going to go with what they came up with. I know they've changed the joint and I also know they didn't do it for production economy reasons---they had a problem. it wasn't a big enough proplem to do a recall, but they did spec the newer bolts for service on the older machines. The torque specs have a tolerance. From the factory, some bolters fer at one end of the tolerance, some at the other. The variation tends to be sinusoidal. it may be that only fasteners at one extreme of the tolerance had problems. on solution is to tighten the tolerance. But this is costly. Another is to change the fastening system to be more reliable across the tolerance range. I suspect this is what they did. The fastener will distort enough throughout the tolerance range to give acceptable locking.

You can set up one bike and reuse your fasteners and have absolutely no problems. You can also buy one lottery ticket and win the lottery. it's a statistical game either way and you really don't know what the statistics are. BMW does know. If there is a problem they hear about it.

BTW, you mention you have seen a lot of drive shaft bolts come loose because they weren't tightened enough. Were you there when they were tightened? How do you know they weren't tightened enough? (aside from simply assuming it---ie, some seriously circular logic). What is inarguable is that you have seen loose drive shaft bolts. (I ain't gonna call you a liar). it could very well be that they were tightened just fine...but they were re-used. Do you really know the history that caused the problem?

You can say you are a professional mechanic but if you don't follow a spec on something like this you aren't one I would patronize. You might be re-using conrod bolts too. if I want an engineer I hire one. i expect a mechanic to be exactly that even though many (like many machinists) feel they need to play engineer for...I dunno what? Status? In my experience both machinists and mechanics often know things the engineers don't simply because a lot of engineers are clueless about either discipline. But it cuts both ways and when things go wrong it isn't because engineers are trying to be machinists or mechanics.

There are a number of critical fasteners on my bike I have Re-engineered. I changed the material to stainless. It has less strength than 8.8 and has a habit of galling so it usually gets antisieze. My brake caliper bolts are an example. These suckers come in and out every time I take a wheel off. I decrease the torque because of the lubrication and check them a lot. I'm taking the risk on myself. So far they have not loosened between checks. When tight they are in pure shear and a pair of them is plenty for the forces the brake pots can exert. So I don't worry---but they are right out in the breeze and easy to check.

For starters, the bolt washer WAS a problem but loctite OR new bolts isn't going to help that issue either.

How do I know that the bolts weren't tightened enough when they came loose. Because I have never seen one come loose when I knew it was tightened right. Deduction. Plus it's not just my experience I am relying on but a number of other professionals.

Any professional that plays by the book 100% of the time is not being professional. The book is a great source of info but it is far from perfect. BMW is not a religion. Even religious zealots pick and choose what parts of the bible they are going to follow. A good mechanical zealot SHOULD do the same thing out of any manual. That is unless he finds one written by god. Personally, I will replace those bolts any time someone insists. Sometimes the used bolts need replacing anyway for being damaged. Other than that, all it is going to do is increase their bill but BMW knows that!

[Wirespokes]

Originally Posted by supershaft

For starters, the bolt washer WAS a problem but loctite OR new bolts isn't going to help that issue either.

How do I know that the bolts weren't tightened enough when they came loose. Because I have never seen one come loose when I knew it was tightened right. Deduction. Plus it's not just my experience I am relying on but a number of other professionals.

Any professional that plays by the book 100% of the time is not being professional. The book is a great source of info but it is far from perfect. BMW is not a religion. Even religious zealots pick and choose what parts of the bible they are going to follow. A good mechanical zealot SHOULD do the same thing out of any manual. That is unless he finds one written by god. Personally, I will replace those bolts any time someone insists. Sometimes the used bolts need replacing anyway for being damaged. Other than that, all it is going to do is increase their bill but BMW knows that!

I agree with SS - The bolts don't need replacing if they're not stretched and in good shape, and they don't need loctite if torqued properly.

Simple as that!

I haven't had any come loose - and that's even from before the days I was able to torque them and found out the specified torque was more than I previously thought. Up till then I used a long ten mm box wrench and applied enough force to feel really tight to me. But the specified torque was even higher than what seemed reasonable to me. Maybe it made a difference the threads weren't totally clean - in which case, any oil will reduce the required torque value. So maybe I was getting them to the proper torque.

But the point is that they don't come loose when properly torqued.

And to aid understanding here - the reason for replacing bolts is that either the head can shear off or the threads stretch. Frankly, I've never even heard of a head shearing off, so that's not an issue. And the threads stretching? That's easy enough to check - if the bolt threads in by hand, it's not stretched.

[Les_Garten]

Originally Posted by Plaka

All fasteners that are intended to lock by deformation are specd' one time use only.

I pretty much agree with you here except for the ALL comment.

That goes against what ARP told me about the fancy Rod Bolts I bought from them for my Porsche 930.

They can be torqued by Ft Pounds or a stretch spec.

They also advise unlimited torque cycles.

I guess they are made so well and so over spec'd they can advise this.

Just thought I would advise this before some folks jumped on the ALL statement.

I still stand by my Cost vs Catastrophe analysis.

Now maybe we need ARP drive shaft bolts...

[disston]

I use Blue Locktight on old bolts because I'm cheap. May not be perfect but it's a damn site better than the washers BMW gave me originally that I had to pick out of the rubber boot. Other than the time several washers broke and two bolts were loose I've never had the short bolts with Locktight and no washer come loose. I replace the bolts every other time if I think of it.

[Plaka]

Originally Posted by Les_Garten

I pretty much agree with you here except for the ALL comment.

That goes against what ARP told me about the fancy Rod Bolts I bought from them for my Porsche 930.

They can be torqued by Ft Pounds or a stretch spec.

They also advise unlimited torque cycles.

I guess they are made so well and so over spec'd they can advise this.

Just thought I would advise this before some folks jumped on the ALL statement.

I still stand by my Cost vs Catastrophe analysis.

Now maybe we need ARP drive shaft bolts...

Point taken. I suppose it is possible to come up with a combination of alloy and geometry that would do it.

[Kt-88]

This is getting silly. If it's a matter of a n00b to the marque such as myself looking for airhead tips and tricks, here's what I got from this discussion: make sure whatever you have in there is torqued and isn't coming out. Not much of a dark secret, but I'll take it.

Assaulting each other's keyboard egos is silly. The other annoying part of this is that it clouds my ability to believe the information given here. If your facts are different than those posted before, I'm a lot more inclined to believe you if you simply post them and don't worry about their defense.

Anyway. Thanks (from a n00b) for taking the time to share your information.

[Plaka]

Originally Posted by Kt-88

This is getting silly. If it's a matter of a n00b to the marque such as myself looking for airhead tips and tricks, here's what I got from this discussion: make sure whatever you have in there is torqued and isn't coming out. Not much of a dark secret, but I'll take it.

Assaulting each others keyboard egos is silly. The other annoying part of this is that it clouds my ability to believe the information given here. If your facts are different than those posted before, I'm a lot more inclined to believe you if you simply post them and don't worry about their defense.

Anyway. Thanks (from a n00b) for taking the time to share your information.

Well I'm sorry to have started a minor sht storm and I regret it. I probably shouldn't have but I got a long memory and..well..nevermind.

But I'd take a little more a2ay from it that what you claim. Opinions differ and it can be very useful to know what different positions are. Snowbums site is one of the two most G-d awful sites I have seen in 20 years on the net, but he knows more than a little, even if you have to fight through his style to get to it. This is not unusual and I often have to remind myself of it---people with annoying styles can have valuable contributions. Engineers really hate to be wrong so figure BMW is playing the most conservative hand. You wanna play that hand do it like they say. (just beware of some of the truly outdated stuff, esp. w/ respect to lubricants).

A good read is To Engineer is Human....

http://www.amazon.com/To-Engineer-Is...ineer+is+human

Outside of that you have your usual thundering gurus and their various opinions. Here I tend to consider how people arrive at their opinions. I'm looking for some intelligence as well as a familiarity with a scientific discipline. The latter invariably accompanies a familiarity with experimental design and methods, formal logic, some stats, etc. This puts many at a disadvantage. They can be damn fine wrenches but poor with words or even understanding why the things that work for them work. This doesn't mean they should be ignored, but I do look for corroboration of their ideas elsewhere.

What I've taken away from this piece of the thread is not only some other opinions on the matter that I wasn't aware of, but also the knowledge that I could, in a pinch, do things otherwise and get away with it, at least for a time. I have no intention of changing my methods in general; I play that conservative hand.

As a side matter, I didn't know about locktites(TM) resistance to hot oil before I looked into some of the other properties.

Insomuch as I have spare boots, and clamps, I also always keep 4 new bolts on hand and replace them when used.

(I've also never taken a bike I own to a mechanic, any mechanic. A tranny or a rear drive yeah, but the whole bike, no way)

[kbasa]

Alright campes. Lets all go back to our corners and think about unicorns and rainbows for a little bit.

Thanks.

Dave

[brittrunyon]

WHAT HAPPENED TO THE "TIPS & TRICKS' THREAD?

WHO GIVES A F#%* ABOUT ENGINEERS?

oops sorry, i guess engineers need love too....................................

[johnalex]

Paul,
If you were to replace the forks on your GS what route would you take?

Originally Posted by adkthunderdog

I am new to the ADV forum but not to airheads, I've paid my bills working on them full time since October 1984. I was BMW certified from then to 1999. I still keep up on the new stuff too. If I can be of any help, I probably have seen or fixed it. I'm currently building a Eastern woods R100GS, light, minimalist, more off road than on. I have been riding this beast off road for 2 years. (see my profile picture) Hello again to all, Paul

[Plaka]

Originally Posted by kbasa

Alright campes. Lets all go back to our corners and think about unicorns and rainbows for a little bit.

Thanks.

Dave

You're reading my mind. But after a couple hours of unicorns and rainbows last night I don't feel too good this morning .

Ah, to have some youth left to misspend...