Airhead "Tips and Tricks"

[Les_Garten]

Originally Posted by Jim K in PA

Thanks Patanga. Nicely presented.

Indeed, awesome site!

[DoktorT]

Originally Posted by patanga

Just loaded this tech tip on our web page. Thought you guys might be interested. The speedo cable boot is often neglected and is a common source of water contamination in to the gearbox. Easy enough to do for the experts but can be a pain for the less experienced. A quick & simple method. http://rter.co.nz/Airheads/airhead_t...ocableboot.pdf

So simple I must say, Genius.

[RonZacapa]

Having ridden airheads for the most part since the mid '80's my observation regarding the double reserve trick.
NOT A GOOD IDEA! when you are running at anything more than 3/4 throttle for any extended period of time. The two fuel taps are just big enough to allow for sufficient flow of fuel at high revs. My 1983 R100 had a 336 degree cam fitted with a decent pair of pipes. Used to go really well and 210-220 km/h on the clock was nothing unusual for it. Coming back from Cape St. Francis with a stiff South Easter pushing from behind I just had to see how fast she would go, the needle on the airhead does go past the 220 mark so I guess I was well onto 235 - 240 indicated when she decided to run the two floatbowls dry. Beeing a mechanically sensitive kind of fellow I decided to cruise a bit slower at the 200 km/h mark and all was good. This was with both fuel taps on.
Long Story Short: The double reserve trick is fine when you are ambling along and cruising at moderate speeds, when caning the beast switch to both taps and your airhead will thank you for it. After all it was designed that way. Other point of concern is that with one fuel tap on the "on side" cylinder will get most of the fuel flow with the opposing cylinder may be running lean at times.

[disston]

I see no point in a double reserve "trick". You have the same amount of fuel, you can only go the same amount of miles. I don't know about you but I am going to stop at the first station I see. I don't need to be told twice I'm almost out of fuel.

[Kai Ju]

The first time I tried it was also the last time. I had turned only the left side on and got 25 miles further just on that side so when it ran out and I switched the right side over I figured I was good for at least another 15-20. Not quite, I got to call my wife 5 miles later from the side of the freeway. Luckily I wasn't all that far from home and it was a Saturday, bad part was I had to get my wife out of bed..........

[gertiektn]

Great tips and tricks all the way. I am working on my 2nd R75/7 project.

I have discover this:

1. take time... if something is not going right.. go and have a beer.. think about it.
2. take lots of pictures... especially on the wiring stuff. (before you pull it apart) connect well.
3. I have found that disconnecting the drive shaft and pulling the engine mounts and sliding the engine a head makes it very easy to unplug the tranny and lube the spline, inspect for leaks and change the neutral electric sender. I think the brass senders are better then aluminum and are available at Hucky's

And lastly I know you all do this.. enjoy.

Jim, Ketchikan Alaska

[Plaka]

Originally Posted by gertiektn

Great tips and tricks all the way. I am working on my 2nd R75/7 project.

I have discover this:

1. take time... if something is not going right.. go and have a beer.. think about it.
2. take lots of pictures... especially on the wiring stuff. (before you pull it apart) connect well.
3. I have found that disconnecting the drive shaft and pulling the engine mounts and sliding the engine a head makes it very easy to unplug the tranny and lube the spline, inspect for leaks and change the neutral electric sender. I think the brass senders are better then aluminum and are available at Hucky's

And lastly I know you all do this.. enjoy.

Jim, Ketchikan Alaska

I'd add a cou8ple things to that:

Once you have a beer do not return to the project until the next day. i dunno about anybody else but I find one beer leads to another and next thing you know I feel all confident when I shouldn't...

A book of wire markers (hardware store or electric supply) is a lifetime supply and if you are digging into the wiring, esp. aftermarket wiring with weird color codes, they are priceless.

Disconnecting the driveshaft is a PITA. I only do it to change the boot. Plus, you have to use fresh bolts of the correct length every time. This adds to the cost of the project. I simply remove the 4 rear subframe bolts, remove the swingarm pivot pins and slide the tranny, subframe. rear wheel, etc. rearward as a unit. You only need about 2"-3" to service the splines. You may or may not have to unplug the rear subframe elec harness, if so, the plug is right by the battery.I got this method from a regular BMW mechanic who was accustomed to beating flat rate on most jobs. He knew the quick way to do things.

When you put it back, wipe the excess grease off the frame and subframe on the inside of the pivot pins. Pins get a wipe and then do a chassis greasing (pivot pins, foot controls, maybe sidestand) on assembly. I always pull the battery box when I do this job and clean up any corrosion and paint it if needed. It's a major corrosion point and yearly inspection is wise. Ditto the cross tube of the swingarm. (use stone gaurd here if you want to get fancy) Replace any hard rubber baby bumpers (I punch my own out of sheet stock. Cheap)

You do want a turned down socket for the swingarm pivot pin locknuts. Keeps them from getting beat up and lets you torque them properly. Like $9 on the net or make your own. (Squareing the open end of the socket is important). The stamped metal tool in the toolkit is BS.

[SERE Nate]

this is so helpful ^_^

[craydds]

Originally Posted by Plaka

Plus, you have to use fresh bolts of the correct length every time. This adds to the cost of the project.

The driveshaft bolts can be re-used, they do not have to be replaced each time. While it may be an okay idea to get new ones, it is optional.
edit: http://bmwmotorcycletech.info/drvshf...oolstorque.htm

[Plaka]

Originally Posted by craydds

The driveshaft bolts can be re-used, they do not have to be replaced each time. While it may be an okay idea to get new ones, it is optional.
edit: http://bmwmotorcycletech.info/drvshf...oolstorque.htm

Both the Haynes and Clymer manuals state that the bolts are the stretch type and must be replaced every time. The BMW factory manual says nothing but it also says to use the spring washers under the bolts. Insomuch as those spring washers (and the longer bolts used with them) have been superseded on all models (and you retrofit with the newer bolts on models w/ the spring washers) the BMW manual is out of date and cannot be relied on. I imagine the matter was covered in a service bulletin.

Snowbum chooses to reuse the bolts but also notice he advocates checking them all the time as well as using locktite. The bolts are supposed to be installed dry so the locktite will screw up the torque---probably worth ignoring if you are re-using the bolts. Checking them all the time (and if they come loose things can get pretty expensive) is a pain in the butt. You need to clean everything (like scrub with a toothbrush) before opening the boot and then they are kinda pesky to tourque. Why go through this? (Bob 9whom I like BTW) is something of a contrairian. He'll say to do something differently just for the sake of it. He's quite knowledable and in this case I agree with him 100%---if you chose to re-engineer that fastener you better check it a lot. Unfortunately Bob doesn't exactly mention what a "regular interval" is...and if he knew he would. 1000 mi? 2500mi? 5000 mi? This is the problem with pull-it-out-of-your-butt engineering, you start from scratch and only know where you are when things fail. You get to observe one bike for failures. BMW on the other hands gets to monitor hundreds of thousands of bikes for failures. They start out with their best educated guess like anyone else and then if things are failing they revise their solution to the problem. Every joint on every motorcycle didn't fail. But some did and this resulted in the change in the fastener spec. I like letting other people be the guinea pig when the consequences of failure are expensive and not covered by warranty.

The bolt is intended to deform a certain amount at the specified torque when installed the specified way. It works and doesn't come loose and doesn't require regular inspection. Why screw with it? (note: most of that deformation is in the threadform, the overall stratch of the bolt is very small.) BMW knows all about locktite and often supplies certain bolts with it pre-applied. If they liked that solution they probably would have gone with it. They don't like lawsuits, warrenty claims or any damage to their reputation. So they are conservative. maybe locktite subjected to heat and hot oil didn't seem so wise?

The bolts cost $1.07 ea (bobs BMW) which means that moving the engine forward and replacing the bolts is going to cost you $6.10 or so. It's a job that should only cost you .10 (for the lube). if you don't replace the bolts you A) incur risk that you wouldn't otherwise and B) incur more work on a regular basis to minimize that risk. Given B) how is moving the engine forward saving work and effort?

BTW, WTF is a "good grunt"?? Torque the damn things. If you can't do it right, (put a critical and difficult to inspect fastener on spec) don't do it.

[Beemerboff]

Totally wrong on Loctite screwing up the torque - Locktite is formulated so that the required torque stays the same.

Achieving that was the biggest problem the makers of Locktite faced when they originally formulated the product.

Unless otherwise advised, all torque figures are for clean and dry threads, so there is never any need to state that - it is only when you oil or lube them that it has to be stated.

IMHO if you cant afford or just cant bring yourself to fit new bolts each time I think you should seriously consider if you should be riding a bike at all, but I appreciate that not everyone will agree with this viewpoint

[disston]

Originally Posted by Beemerboff

Totally wrong on Loctite screwing up the torque - Locktite is formulated so that the required torque stays the same.

Achieving that was the biggest problem the makers of Locktite faced when they originally formulated the product.

Unless otherwise advised, all torque figures are for clean and dry threads, so there is never any need to state that - it is only when you oil or lube them that it has to be stated.

IMHO if you cant afford or just cant bring yourself to fit new bolts each time I think you should seriously consider if you should be riding a bike at all, but I appreciate that not everyone will agree with this viewpoint

Would you care to cite any sort of authority for this statement? Web page or something from anyone else. You are the first person I have heard say that Locktight was formulated to not screw with torque settings. I find it hard to believe for this reason. You may be right, I guess I would like that, but never having heard this before it's hard for me to believe.

[Plaka]

Originally Posted by Beemerboff

Totally wrong on Loctite screwing up the torque - Locktite is formulated so that the required torque stays the same./snip

well, Snowbum mentions it on the page already cited.I agree and also agree the effect is small.

if you look at the data sheet for 242 locktite (blue, medium strength) they list the product lubricity. Notice it is a negative number. That means it is decreasing friction ("K" is a coefficient of kinematic friction).

See: https://tds.us.henkel.com//NA/UT/HNAUTTDS.nsf/web/4F5DE4CF912A71D7882571870000D60D/$File/242-EN.pdf

Interestingly on the data sheet for the low strength purple, the K is listed as -10 to +10. There is also the statement:

"(In critical applications, it is necessary to determine the K values independently. Henkel corporation makes no warranty of specific performance on any individual fastener)"

http://www.loctite.sg/sea/content_da...18_222MSEN.pdf

In other words, figure out what it does to your fastening torques for yourself if it really matters. Makes sense to me because that stuff is usually used on very small fasteners and at those scales the magnitudes of friction effects is greater.

if you think about it, coming up with a fluid that has no lubricity on any fastener material at any size and at any torque is not possible. You would have to add an abrasive of some sort to reclaim the friction and the effect of it will not be linear across materials, sizes and torques.

Of note on those data sheets: locktite blue doesn't mind 257F engine oil. So now I know that one.

personally I use locktite green a lot, the penetrating stuff. You assemble dry and then apply it. Not that I care about the torque effects, it's just simpler and half the time I forget to put it on some fastener anyhow.


To come back to the OPs original ideas: My point about replacing the bolts was minor---you can blow $6 on a cheeseburger anytime. I do the transmission rearwards w/subframe routine because a factory trained and highly experienced mechanic does it that way. He has to make a living at it, and does. if there was something quicker and easier, he would know about it and do it that way instead. The quicker he is the more he makes.

Just thinking it through I'm not sure how far the engine can move forward before something hits. i'm seeing the top cover maybe coming off which means removing a coil. I dunno. I also imagine I'd have to make some sort of dolly (wheels on my jack go the wrong way). And then put a jack on the dolly to take the load off the engine bolts. Then the sidestand falls off (it goes on one engine bolt) and if the motor falls off the jack I just bought a bunch of engine parts...Um, think I'll stick to the way I've always done it.

But it's good to hear some other ideas. Even if I end up not liking them for some reason I do always think about them

[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.

[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.