Lubing Steering Head Bearings on BMW Airhead Motorcycles
Cleaning and lubrication of the steering head bearings should be done at a scheduled mileage/time but most let it go until the steering has a ‘notch’ felt in the straight ahead position. This procedure was developed specifically for a 1983/1984 R100RT, but is similar for all Airheads. I advise you to read this procedure through before beginning. Cleaning and regreasing MAY WELL eliminate “notchy-ness” that SEEMS to indicate need for new bearings and outer races. It is best, but not mandatory, to do this procedure after installing new balanced tires, as road crown and tire squaring wear, and balance, might have an adverse effect on trying to make final on-the-road adjustments. This is not hardly just for the front tire….most riders do not know that a squared-off REAR tire is THE most common cause of wobble and weaving from the tires. The author has usually, but not always, done this procedure to his own bikes after installation of a new front tire, but when the wheel is off the motorcycle. If your REAR tire is not squared-off considerably, it will be OK for the final procedure, which are riding tests to get the preload adjustment ‘just right’. It is possible to do this procedure with the front wheel in place, usually that means having the front wheel hanging over the edge of a curb, or the centerstand is in use and on a piece of wood, so the front end can be dropped a couple of inches.
Cleaning and lubrication of steering bearings is not at all difficult, but if a bearing is found truly bad, replacing them is more labor intensive, as part of any fairing must be removed, and possibly brake piping, cables, etc. Contrary to some popular belief, our BMW steering head bearings of the tapered ‘Timken’ style may well last over 200,000 miles. If the bearings/races/shells are in good condition and properly greased and adjusted, the steering will be light, smooth, without any straight ahead notch. You likely will not find out if the bearings are really bad, that is, in need of replacement, UNTIL you first try cleaning and greasing. In a SHOP situation, the bearings are not cleaned and lubricated and then adjusted to see if any notch is gone. In a SHOP situation, labor is too costly for that. A shop can not take the time to clean and regrease, and then find out that the bearings really are bad, so a shop always replaces a notchy bearing. YOU, on the other hand, don’t need to do that…..and will often save a LOT of money, and a considerable amount of labor saving is possible.
The general/generic procedure in this Technical Tip is adaptable. The differences between Airheads is mostly minor, with some improvements after the /5 models in the parts and method used to adjust the bearing. The /5 can have the /6 and later type adjustment parts installed. The last of the Airheads, including such as the R100GS, etc., had more involved changes in the adjustments, using a sleeve tool (which you can make for pennies) method of adjusting the bearings, and removes most of the need for on-road testing and adjustment.
I recommend cleaning and relubrication every 50,000 miles or 4 years, whichever comes sooner. Non-faired models (especially if driven in the rain or extremely dusty conditions often) may require more frequent attention. Do not use greases containing moly compounds, they do not work well over time in THIS PARTICULAR application, and will actually start to exhibit notchiness rather soon, as the Moly will clump-up.
Tools: Nothing special, but you will want a 6 mm allen wrench in drive size to fit your torque wrench and you will want a modified 27 mm or 1-1/16″ socket. What you need is actually somewhat dependent on your particular model of Airhead, particularly the R100GS. The normal BMW bike toolkit will suffice for the rest. Read this entire article to see what YOUR particular bike will need.
LUBRICANTS:
Almost any thin-feeling, non-fibrous grease will probably be adequate. It is desirable to use a grease with good smearability, good water resistance, and especially low evaporation/hardening over time. I use Chevron NLG1 Ultra Duty EP, a red colored grease, available from a Chevron Distributor (most Chevron gas stations are NOT distributors, but you can ask if they have that grease). The last time I purchased some, it was available in NLG0,1, and 2. Do not use NLG0. The NLG1 or NLG2 are both OK, the NLG2 being a bit thicker. All are lithium based greases, with tackiness additives, etc. You can use this grease for many other places on your Airhead, INcluding transmission input splines (add moly), and it is very good for wheel bearings and the swing arm bearings. For the rear wheel cup splines (used on twin rear shock models), and transmission input splines or nearly any other splines application, I suggest mixing with about 30% moly (or Staburags or Optimol). If you wish to purchase a moly lubricant, the two I know best (besides military moly lubes which are fine) are Honda 60 paste (77 is fine), and Guard Dog GD525 (NOT GD570). Guard Dog lubricants are now difficult to find, as the Company seems to have disappeared.
Back to the steering head bearings specifically:
You don’t have to have a grease gun, but you MIGHT find it a bit easier to have a grease gun with a grease gun hose and a common grease gun type of fat needle type tip for the hose. Try to find the longer type needle. You may want to get a 90 degree adapter for that needle tip. I used to use a grease gun, now I use my fingers. Minor other items are listed within the procedure.
**In our society of sue-crazy individuals, the usual disclaimers apply and I take no responsibility for your work, nor for any ineptness on your part, such as failure to tighten things!…etc. Airhead Canon #8 (and others) applies!
DISASSEMBLY:
MODIFY this procedure for YOUR particular year and model!! This procedure as follows was done numerous times on a 1983 and a 1984 RT, and also an RS, and a ST and a /5 and /6……and you may find some modest differences on your bike. One of those differences is how the steering adjustment parts at the top look, and are adjusted. You may not have a damper, the wrench sizes may be different…all these things are mostly minor. You will need a simple sleeve for the adjustment for a R100GS type with the small hex top adjustment, and this sleeve can be made from a simple piece of common copper sleeve used in plumbing.
Remove the gas tank. Avoid scratching the paint, especially watch for interference with the opened seat, as on some bikes the left front edge of the metal seat pan is not nice to your tank paint during tank removal. With the tank removed, now is a great time for a full under-tank inspection. If you have an under-tank brake master cylinder, or an electronic ignition….why not service those items now ….a brake fluid change…replacing the heat sink paste…..and maybe clean and silicone grease the electrical connections, inspect the coil towers outsides and insides and the coil spark plug wires….etc.
Remove damper knob center screw, remove knob, spring, plastic spacer. Note that the damper knob is indexed to the shaft flat. You may not have these things.
Remove the small rectangular rubber plug at the fairing, rotate and remove the wire clips that keep the damper ends onto the ‘balls’, then remove the steering damper completely, noting that the large end fits forward/up.
Remove the dress cover at the handlebars. Remove the instrument pod assembly by first fully loosening the speedometer cable ‘nut’ at the cable/pod and pulling the speedometer cable off the pod; then loosening (only) the 3 each 10 mm headed bolts holding the pod to its bracket. Lift up and remove the instrument pod and remove the phillips type screw at the center of the pod’s electrical connector, and wiggle out the cable/connector. Set the pod aside where you won’t trip over it.
Using a substantial sized BRASS or dead blow hammer and the BMW tool kit 36 mm flat spanner called the Dog Bone wrench (suitably thinned slightly at the working end, if need be to fit between bars and top nut), and being careful not to damage the ignition module if you have one (or the ATE master cylinder if you have that), loosen for removal the 36 mm top stem CAPnut. Late models use 41 mm and there is a dogbone wrench with a 41 mm hex end. It is usually NOT necessary to remove the handlebars, nor even loosen them, for the steering bearings cleaning and greasing job.
If you have to or want to remove the front wheel, here are some suggestions: Insert a wood block or ?? spacer at the handlebar brake lever, securing it so the lever can’t be accidentally squeezed by some ‘friend’. Remove the front brake calipers, use baling wire or a bungee to hold them up so as to NOT be hanging from the brake cables. NEVER EVER hang a caliper, even momentarily,
by the hose!!! Do NOT disconnect the brake fluid lines!
It may be that with the motorcycle on a curb edge (or, center-stand on a piece of wood), so the front wheel can hang out well free of the ground, that the brake/wheel assembly need not be removed. The front wheel will only need to be dropped an inch or so. If your front wheel is WAY clear of the ground (say, over a curb), you might want to put some sort of support under the wheel, if it is to be left in place (see next paragraph). At this point, if you ARE removing the front wheel, do so.
Loosen the lower yoke (lower triple-tree casting) allen bolts, that provide the clamping pressure on the fork tubes. Block the front forks from dropping down, with wood or similar under the forks or tire as needed. Remember!….you are dropping the front forks only an inch or so, depending on model, and if faired, etc.
Remove, being careful with that hammer, the 36 mm hex tops from the top of each fork tube at the top of the upper triple clamp plate. They may be under some spring pressure. It is not necessary to remove their center allen head bolts, if you have such. Lift the handlebar assembly and tilt enough to clear the damper rod
in the stem. Fasten the handlebar assembly forward against the windscreen..or..??… using some padding and a long bungy cord wrapped around the windscreen or however you need to do this. Do not remove the fork springs. Now you can remove the adjustment nut using the BMW tool kit hook wrench; your model may be different. Remove the top dust shield. The later models, such as the R100GS use a different method of adjustment, but the basics here apply to all.
A pull from below on the forks may release them downward a tad (adjust wood block under tire as required). You may have to use a piece
of wood (NOT EVER METAL!!) on top of the steering stem, and a substantial sized hammer (I use a small hand-sledge), and give the wood a decent whack as the stem sometimes sticks into the top bearing. When the fork drops adjust the wood block under the fork/wheel to move the fork slightly up. This is necessary as the forks will have to be moved around a bit fore and aft during the cleaning and greasing operation [remember that]. The top inner bearing will be easily removable with your fingers. Wipe the captive inner race, which is in the steering head, and then inspect it with a strong light. If the race looks worn and has fingernail feelable irregularities (like depressed areas), then do not plan on cleaning and lubrication, instead plan on replacing the top and bottom bearings, completely. It is possible to wipe the lower outer race with a rag and inspect it too….I do the inspection with a dental mirror. There is usually enough clearance for a fingertip/fingernail feel of the outer race.
Assuming the race looks and feels OK (a slight discoloration at one or two places DOES NOT mean new bearings are needed), then continue on with the cleaning and lubrication.
This work can be done with even an RT fairing in place. EXTENSIVELY AND THOROUGHLY CLEAN THE LOWER BEARING/RACE AREA. Use lots of strips of lint free rags. I prefer old pieces of cotton bed sheets cut into strips about 2 inches by 12 inches, so as to wrap well around the bearing during the cleaning. Use a SMALL amount of a solvent such as kerosene or paint thinner on the rag pieces (not dripping wet). For the lower bearing area, clean as best you can the entire bearing, shell, and area surrounding. Then a final cleaning with a dry rag. Grease this lower bearing using the grease gun (and needle tip if you use that) as mentioned; or, just your fingers, which works quite well. You will need to use a finger with some pressure anyway to force the grease INTO the bearing; rotate as you go. Be generous with the grease, you can clean the area up after final reassembly. Move the forks around/wiggle, to enable full greasing. Rotate the bearing as you grease. Just keep forcing grease into the bearing, leaving a goodly excess.
You already have removed the TOP bearing, so clean it and the cup/shell/race area. Hand grease the top bearing, forcing grease throughout. The top is easy to do. If you want to, purchase a cone plastic device from an autoparts store, that helps force grease into the bearing.
REASSEMBLY AND ADJUSTMENT:
Before attaching wheel and brakes (if removed): put top bearing, shield cup, adjuster nut, etc., in place, lifting the fork upwards, then lightly tighten the adjuster nut, using the hook wrench (or, if a late model, the appropriate tool). The idea is to bring the entire fork back up into position and have light pressure on the actual adjuster. Attach the handlebar assembly. Be absolutely certain that the handlebar
assembly/top plate, fits properly at the stem area…..as the top cap plug may have a ‘shelf’ machined into it. Attach the two fork top 36 mm hex plugs with any washers. Doing this can take considerable grunt against spring pressure; it will help to use a screwdriver or? into the allen bolt recess to apply downward pressure. It also helps to be sure the wheel is off the ground and not resting on the wood block. DO NOT CROSSTHREAD! Be sure all is lined-up correctly and tighten the two 36 mm
hex plugs at the fork tubes to approximately a turn or less loose.
BE SURE that you DID loosen a couple of turns, each of the two lower triple clamp tube locking allen bolts.
Install the domed top cap nut or nut used on your model. Note!!!…as you tighten THIS top cap
nut later, it pulls on the entire lower assembly threads very slightly in such a way that the slight play in the threads is taken up, so the ADJUSTMENT WILL TIGHTEN. Thus, any adjustment you make means loosening the top CAP nut, making an adjustment below the top plate, then retightening the CAP nut, and THEN checking the effect. You CAN NOT feel-adjust the bearings adjustment, by moving the forks, withOUT the top cap nut being TIGHT. …and you have to have it loose, to MAKE any adjustment. When you THINK you have the adjustment about right (which will likely be looser than you think)….then tighten the TOP nut quite tightly, by hand, using the flat wrench, but NOT using the hammer, while moving the fork back and forth to take up any grease spacing, so to enable a test on the forks movement. Then very thoroughly tighten the top CAP nut (the specifications are 120-130 Nm which is 88-96 footpounds), and then if the forks are still OK, then tighten the lower triple clamp allen bolts. The stock /5 fork adjustment uses a small thin round steel rod that was part of the original stock tool kit, to hold one part of the adjustment (and there is a split knurled unit) while adjusting the other, and then you have the top cap too. The /6 parts can be fitted, to make it a bit simpler. The R100GS uses a sleeve to make the adjustment, via a top hex, and you can refer to a manual on what/how this is done.
You can twist the fork tubes in the triple clamps, which gives you nasty STICTION, if you try a lot of force in loosening or tightening the tube top caps or the center nut, and a reverse torque tool is a nice thing to use. My website has photos of such a tool (common large screwdriver is OK) in use, see
http://bmwmotorcycletech.info
I advise using my website description/method for a reverse torque tool tightening. It is a good idea even when loosening things in the beginning! YOU DO NOT WANT TO TWIST THE FORKS.
Here is the adjustment procedure, in depth:
The motorcycle should be on the center stand and the front wheel/forks assembled and not touching the ground. The first try at adjustment should be to the point that the front end exhibits, JUST BARELY, no perceptible drag; or, to the factory specified drag using the factory tool you won’t have anyway! The only friction should be from stem bearing grease, fork tubes rubber boots glued to the fairing, if you have those, and cables/wiring. The PROPER adjustment will be the point, with the TOPCENTER CAP very tight indeed (at or almost to normal), that the forks NOT QUITE fall by themselves to one side stop or the other, if fork movement is started by you by a quick nudging of a bar end. Just a bit of movement, even maybe a third or half or so of the possible movement amount the fork stops allow. I usually install the top CAPnut, tightly as I can with my hand and the flat wrench, and then a tad more with
the brass hammer before the test. You will notice that this capnut has a MAJOR effect on the adjustment nut setting, so loosen the capnut and readjust the adjustment nut…and repeat this…until conditions are correct. Very early models of Airheads are more touchy about how the adjustment works; very late models have a better adjustment method, and those in the middle, a /6 and later but not the R100GS, are in the middle group.
With the capnut tight from use of the brass or dead-blow hammer, if you turn the bars one way or the other from the straight ahead position, they should JUST barely fall, perhaps half way, to one side. At this point, turn the bars slowly from fully right to fully left. If you feel roughness or a center notch, you need new bearings and races. Have a fun day! Finding a bad bearing this way is very UNlikely, since you looked at and felt the outer races earlier in this procedure.
Inspect to be sure that wiring, cables, etc., do not interfere with front end movement. Assemble everything except the gas tank and steering damper. Leave the lower triple clamp allen screws loose, but tighten securely and tightly the two top triple plate [36/41 mm hextops]. Mind the caution on twisting the tubes in the triple clamps….that often happens when someone tightens the top center or tube nuts with the forks at a mechanical turning stop.
Now is the time to tighten the lower fork triple clamp allen bolts, and to do a THOROUGH CHECK-OVER, to be sure you have assembled everything and tightened everything, except any hydraulic damper and instrument pod and gas tank. If cleaning and re-coating the ignition module or cleaning connections or changing brake fluid, etc…. finish those jobs now.
****DO NOT FORGET TO TIGHTEN THE LOWER TRIPLE CLAMP ALLEN BOLTS!!!!!
Recheck that the steering feels as it did…just falling barely to perhaps half way either side if nudged that way, or, just a bit more. On the ST and GS, and other naked non-faired Airheads, you may want it to fall just about all the way, but barely. Assemble any damper, pod, gas tank. AGAIN check that all looks OK, no cables are interfering with steering, etc. If you have a fairing and are assembling the hydraulic damper, with those wire clip keepers, you will need patience, and likely a small inspection mirror. Grease those ball ends before assembling the damper. Put a tiny amount of contact cleaner or silicon spray onto the instrument pod electrical plug contacts, and don’t forget the screw that holds that plug in place (and do not over tighten it). AGAIN, recheck all those bolts, screws, etc. You DID tighten the lower triple clamps? Fork tops?
ROAD TESTS:::
Inflate tires properly. Remove saddlebags, and any rear trunk if not too much a bother. Road test, withOUT a passenger.
The first road test is for low speed weaving. For ALL tests, any damper MUST be turned off! You will likely want to do this initial road test at about 25 to 35 mph. If you go too fast you CAN NOT feel things properly! If your bearing adjustment is too tight, you will find the steering a bit heavy, a tendency to weave and not track smoothly. If you have this condition, remove the gas tank to protect it, loosen the top capnut and loosen the adjuster nut a SMALL amount, perhaps a FEW degrees. Re-tighten the top cap, put on the tank, do another test. YOU DO NOT HAVE TO LOOSEN THE LOWER TRIPLE CLAMP ALLEN BOLTS for such a minor tiny adjustment. If things feel correct 20 to 40 mph, try removing hands from the bars and giving one bar-end a medium light hit, at about 35 mph. Any tendency for an INcreasing oscillation back and forth is cause for investigating tire balance, tire condition, wheel bearings, etc. Any slight oscillation (also called a wobble) should be damped out easily by simple placement of the hands back on the bars. ..without trying to hold the steering from oscillating. If not as described, you have a problem! The IDEAL adjustment is just barely no weaving or heaviness feeling, or, the slightest heaviness/weaving.
IF, by any chance, you have a sidecar equipped Airhead, the best adjustment is rather considerably tighter, and is done by educated feel, road tests usually not needed. An Airhead to be used with a sidecar, but with it unattached, will definitely noticeably weave at low speeds.
High speed tests are not for the faint-of-heart. They are usually done by beginning at around 10 mph and increasing in stages to about 90. Every 10 mph, take hands off bars and tap them a tad, and check stability. NOTE that if you have a squared-off REAR tire, I recommend AGAINST such high speed tests.
Airheads, particularly the old ones with two sided swing arms, as this procedure addresses primarily, have an effect called, among other names, Rubber Cow [from the German word gummikah], or a hinged-in-the-middle feeling. This effect is a weaving feeling, often pronounced on the RT and RS models with bags and backrest/tour trunk, at around 80 mph and up, especially in downhill sweeping turns. This effect is primarily caused by wind effects on those accessories, and the not very stiff rear suspension and the rear subframe design. BMW improved this with the single sided swing arm and further improvement is possible with better shocks, springs, and modifications to stiffen the frame (the modifications of welding tubes to the swing arm are generally not of much use). Surprisingly, a good fork brace and ESPECIALLY a stiffer top steering plate (on the steel top plate models) can help. If your bike exhibits this feeling at speed, particularly downhill turns, it is probably not the steering head adjustment. Any tendency for high speed instabilities, particularly of the DIverging (increasing) oscillation type are greatly increased by weight located behind the rear axle, and even made worse by saddlebags and windscreens and fairings. A HUGE effect is seen with squared-off rear tires. For most, a serious diverging oscillation will make you want to stop at a church and pray. Take the hint and watch for improper motorcycle loading.
NOTE: in every instance of any 2 wheeler Airhead I have adjusted the steering on, the proper adjustment is hardly any noticeable weaving at LOW speeds….not high speeds…..and there has never been a high speed problem exhibited from that particular steering head adjustment. YMMV!
It is WAY better to have the forks very slightly too tight at the adjuster nut, putting up with a slight trace of low speed weaving, than too loose.
Once you have done this procedure and gotten the steering adjusted correctly, you likely will get it right the next time without having to do these road tests. I wish to emphasize that once you are close to the
proper adjustment, a very tiny change of only a few degrees on the adjustment nut will make a large change in effect.
A word of caution here about diverging fork oscillations (high speed diverging wobbles). Due to the interactions of gyroscopic and centripetal forces and other effects, the energy forces available at speed are fairly high. If a serious wobble begins, and forceful hands-on-bars pressure does not diminish or eliminate the wobble, you may well have a spectacular accident. If you have adjusted your forks EVEN NEAR correctly, any fork induced oscillation from being too loose, will be dampened easily. If your tires are road crowned, under inflated, way out of balance, squared-off, ETC., you can STILL have a serious oscillation problem. Approach road tests carefully, deliberately, in stages of increasing speed, and this will almost always eliminate serious problems.
Additional Notes:
The road test really is necessary, and I have always felt that the steering head is best set so that the smallest amount of slow speed weaving effect was JUST BARELY noticed. But, if one wants to set the bearing ‘officially’ , it is done with a torque wrench. There are a number of ways to go about this, but here are a couple of simple ones for the old Airheads. NOTE that the top cap nut must be fully tightened BEFORE you take these readings, as tightening that top locking cap nut tightens the lower adjustor against the bearings, taking up the actual play in the threads.
Acorn Top Cap final torque is 88-96 footpounds (120-130 Nm).
Method #1: Use a 36 mm socket and an INCH-pound torque wrench.
Method #2: Modify the wrench that came with your bike….this is the flat dogbone wrench that has the flat 36 mm end and the 27 mm welded box section. For those folks without this tool, the BMW part number is 71-11-1-230-684; updated to 71-11-1-237-857…..I have made note before about grinding the 36 mm end slightly thinner to allow it to fit between the handlebars and that top nut, without loosening the handlebars. The 27 mm end is an emergency swing arm nut (and some nuts on sides of headlight buckets) tool and not overly strong for swingarm nuts, so I never use that end. It also fits some ignition switch nuts. For a torque wrench adapter for the steering adjustment, you need to modify this flat wrench so that you can attach a torque wrench to it. This factory adjustment tool is a 36 mm flat box end wrench with the wrench coming backwards, and then folding upwards and back over the center of the 36 mm top cap nut. I doubt anyone is going to purchase that wrench. You can modify the tool tray dog bone 36/27 wrench, part numbers above, by drilling and then hand-filing a square drive hole in it. You could also just weld a square drive to it, but that takes up more room in your bike tool roll. You will need to REDUCE the torque wrench setting by a factor that has to be calculated from the working length of the torque wrench and the working length of your modified tool.
In all instances, be careful, as movement of cables and so on will influence the torque reading. The OFFICIAL adjustment for the preload on the bearing….the torque setting (this is NOT the top cap setting!) (wheel off ground, no cables, blah blah)….is 350 Ncm….which is about 31 INCH pounds…that is 2.58 FOOT pounds…so you can NOT do this with common torque wrenches used for the head nuts, etc. This is a
running torque value….that is, turn the forks to the left maybe 30 degrees or so, then use the torque wrench to start rotating the forks towards the center position. The running torque value is that value DURING movement. If you have all the cables, etc., attached, you will have to make an estimate of the higher value you will need to set to.
Still, no guarantees that the end result will be proper, so a road test is needed. I don’t bother with the torque readings. I do road testing.
NOTE!….For the drum brake front ends, the steering head is officially to be at 1.9 +-0.2 footpounds. For the single or dual disc brake front ends, the steering head is to be at 2.6 +-0.14 footpounds. These figures are from the BMW factory. Be my guest in trying to figure out why there are two specifications.
It IS possible to modify the dogbone wrench to enable an inch-pound wrench to be used. Yes, use above figures and multiply by 12.
I have tried using a torque wrench, and it does work out OK, but not as good as with road testing and adjustment from those road tests. I also have found that since the cables are almost certainly not going to be disconnected, nor wiring disconnected that all have an effect on the steering, that about 4 ftlbs was about correct. It is tricky.
Revised 05/21/2017
Robert J. Fleischer, aka SNOWBUM
https://bmwmotorcycletech.info
