snowbum – Page 3 – Airheads Beemer Club

Lubing Steering Head Bearings

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.

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Front Forks – Alignment, Braces, Cleaning, etc.

PRELIMINARY & INTRODUCTORY INFORMATION:

Because the rear tire wear condition has such a MAJOR effect on handling, I recommend the steering be cleaned, lubricated, and adjusted, only at tire change time, after a new rear tire is installed, and perhaps 100 miles or so is on it.

Be extremely cautious about using BMW parts books sketches; same for Haynes and Clymers manuals. Various parts may be shown on any particular sketch or drawing that are only used on some models or some years, and, in some instances, are no longer used at all. The order of assembly, or placement, may not be as on the sketches.

You may want to read/review the following article by Brook Reams, it is lengthy, but has many photos in it that I do not supply in my article; and Brook has a somewhat different approach here and there. Review his article, you may want to do that more than once ….and maybe once more after reading my article.
http://brook.reams.me/bmw-motorcyle-rebuilds/1973-bmw-r755-rebuild-project/31-bmw-r755-install-and-align-front-forks/

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Front Fork Oil

Discussion of Oil types and characteristics.

The following article SHOULD BE USED WITH: http://bmwmotorcycletech.info/viscosity.htm. That article has information that REALLY SHOULD BE READ…either NOW, or, after reading the below article!

I prefer Spectro’s fork oils and suspension fluids. They are of good quality, have low stiction, wide temperature range (excellent viscosity index), & the viscosities can be depended upon. Due to how specified, & lack of stiction fighters in some oils used commonly in our front forks & other characteristics, you are better off with a real fork oil like Spectro’s ….especially the full synthetic or part synthetic fork oil. For fork oils & suspension fluids, the various manufacturer’s do not agree on measuring viscosity; sometimes they don’t do more than give some sort of approximate SAE grade value. Viscosity measurements & temperatures are vastly more accurate between manufacturer’s for engine & gear oils; not so, apparently, for many suspension & fork oils. Because of these various things, and other reasons I won’t bother to get into, I highly recommend you stay with one manufacturer, this is particularly so if you are trying different viscosity grades.

I have not yet done extremely long period testing to find out what oils, or ingredients (esp. mineral vs synthetic), are causing the deterioration of the ‘bumpers’ at the bottom of the forks. Until someone does such a test, or an accelerated test (increasing the temperature?), it is best to simply change the fork oil at reasonable intervals.

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Transmission Input Spline Cleaning, Lubrication, Hints

Applicability: All BMW Airhead models; with some useful information for any splines-driven dry-plate clutch.

Why do it: (1) Smoother shifting; (2) Avoid wearing out expensive parts with expensive labor to repair damage; (3) Avoid suddenly spline failure

When to do it: Depends on year model and conditions you ride in, but probably every 12000 to 35000 miles.

What are you going to do: Unfasten the transmission, move it slightly backwards, clean and lubricate the transmission input shaft splines, and then reinstall transmission. You will probably do other work at the same time, described in the text that follows.

NOTE: While an adequate job can be done by just moving the transmission backwards, a 100% job means removing the transmission from the motorcycle. THAT can be put off until you have another reason for removing the transmission.

Required Skill level: Lower intermediate or better

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Spline lubricants

Airheads need scheduled lubrication on transmission input shaft splines (never grease the clutch disc splines themselves); and, rear wheel cup splines and associated rear drive output splines on the twin-rear-shock models.

Numerous lubricants have been tried in many different climatic and riding conditions, over many years. Some newer lubricants are still being tested. There does not seem to be any magic, perfect lubricant for these places. BMW has specified quite a few lubricants over the years, such as Staburags, Optimoly, ETC. The author has never believed these lubricants were as good as some others, at the times BMW had those recommendations. The author, and others, have done long-term testing on various lubricants. This article you are reading no longer lists these lubricants, nor recommended lubricants, as the latest information will be found HERE:
http://bmwmotorcycletech.info/chemicalsetc.htm where the author keeps the information up-to-date. The spline lubricant information is at item #6A in that article.

Later model (exact year and models are unclear, probably late 1980’s) transmission input splines are SUPPOSEDLY nickel-plated and do not require cleaning and relubrication quite as often, but 30,000 miles seems the practical LIMIT, and for earlier ones perhaps 20,000 is the limit. Best you do it before these mileages, at least once, and then, upon inspection, adjust the interval for the next clean/lube. Once a spline shows rusting, you are LOSING METAL! The transmission input splines are fine-pitch and not very deep….you do NOT want them to fail!

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Clutch – Maintenance

Warning! Warning!! WARNING!!!
Under no circumstance should the flywheel or clutch carrier on any model be removed without first blocking the crankshaft from moving forward!! http://bmwmotorcycletech.info/flywheelremovalwarning.htm

You must block the crankshaft! Do not take a chance on serious damage to the engine!

Many have removed & replaced an Airhead flywheel or clutch carrier without blocking the crankshaft with no problems. My advice, very strongly given here, is to take a minor amount of time & make & use at least my simple crankshaft blocking tool. If you do not use some sort of crankshaft blocking tool, & your crankshaft should happen to move forward enough (does not take much pressure nor does it have to move far!) to have one or both of the thrust washers fall off their pins, you could cause very serious damage as you attach & bolt-up the flywheel or clutch carrier. Even if you do not cause serious damage, if the forward thrust washer drops, you may be unable to get it back on its pins without a very considerable amount of work. Do not take a chance!

Since it is a must, in my opinion, to mechanically block the crankshaft from moving forward at any time during the process of removing or replacing a flywheel (or clutch carrier as it is called on 1981+ including some 1980 models), you need to know how to best do that.

This can be done in several ways. I recommend you do not use ‘a towel’ between the front cover & the alternator rotor, as is sometimes done. I recommend a simple & neat method …just make a tool out of a piece of Allen wrench material, weld a disc (fender washer) on one end, making the length such that the Allen end fits into the alternator bolt, & the disc end presses against the inside of the outer timing chest cover. Usually 3/4 inch overall. The length should be such that there will be some light pressure applied by the cover to the tool, the cover being screwed back towards the engine lightly (but not touching the engine case). The tool should be just long enough that the cover can not be fit fully home all the way. Obviously you don’t want to tighten the outer cover very much & you do not need to!

A further treatment of how to make this tool, & a photo of it, is in http://bmwmotorcycletech.info/tools.htm , as item #8A. Note that making the tool requires a very small amount of welding. If you do not have a welder, or do not wish to have the tool made that way, you can just use a piece of allen wrench. The tools article also has photos of the clutch disassembly & assembly tools …you may need three if you have an early model; although three common bolts work well.

At this point I strongly suggest you go look at: http://bmwmotorcycletech.info/flywheelremovalwarning.htm

Whatever tool you use, be sure it cannot rotate such as to loosen its pressure on the inside of the outer cover if you rotate the flywheel in either direction. The advantage of my tool is that it is unlikely to allow the alternator bolt to loosen if the tool is made and installed correctly, as you rotate the flywheel. Be sure the tool is not ‘captured’ by raised grooves on the inside of the cover, etc. Think!

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Alcohol-Proof Float Kit

The MAIN advantage of these kits is that you will likely never have to replace floats. That does NOT apply to the float needles, of which there were two basic types. The VITON tipped ones have the same easy-to-lose fine wire clip as on the stock carburetors. That clip insures positive float needle operation when the needle should be leaving the needle seat and allowing fuel to flow into the bowl.

If the original floats (which DO AGE) are already really bad, and/or the float needle is already bad, things will certainly improve with PROPER installation of these PRICEY kits! Installation is, however, somewhat tricky. IN MY OPINION, installation of these kits when the old parts were worn, often considerably, is the HONEST & TRUE reason that SOME find improvements with fuel mileage after installing the kits.

Adjustment of these dual-independent float kits is more involved than with the stock floats. These kits can cause $$$$ problems, so, please read all of this article.

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Synchronizing Carburetors

The following information specifically applies to carbureted twin cylinder two-valve BMWs, of the type known as “Airheads”, as manufactured 12/1969->1995+. Some of the information may be applicable to many other motorcycles, and even injected models, and to even single cylinder and two stroke engines. The method is applicable to BMW models before the above dates, and while the shorting method works for ALL, you CAN use the vacuum methods for those earlier models with, or install, vacuum ports.The author has used these methods on a wide variety of engines. The author is NOT responsible for any electrical shocks, nor other consequences, for any ineptness on your part in failing to understand and perform procedures properly and safely.

Quite a few decades ago many mechanics used a device called a Uni-Syn to balance carburetors. It was usable on almost any carburetor, and it was usable on most injected models (rare, then). Sometimes a minor modification was needed to allow the Uni-Syn to properly mate with the input area. The Uni-Syn was a specially machined or cast metal plate, rubber on one side to allow some pressure-sealing against the air intake side of the carburetor or injector, and an ADJUSTABLE venturi built into the plate, and attached to the venturi was a glass or plastic tube that had a floating ball in it. Properly used, this device would take accurate relative readings of the airflow through a carburetor or injection intake; then the device was transferred to the other carburetor (usable on engines with many carburetors too). I do not know if they are still available, I have one, and treasure it, as an antique! Treasuring some old tool does NOT mean I use it nowadays!

I do not! I have not seen one used, except in my own shop for some sports cars or 4 or 6 cylinder motorcycles, since the mid-1970’s, except to demonstrate its use. Mechanics had a lot of pride on their ability, without instruments, to listen to the engine; adjusting the idle mixture screw for a smooth idle, then setting idle rpm, and going back and forth until they ended up with the proper idle rpm and idle mixture adjustment. Some very experienced mechanics would even take bets on being able to synchronize a BMW Airhead engine without any special tools….and often made up stories about what they were doing….which, in truth was simply listening to the transmission internals rattling around at idle rpm (which they do, when the oil is hot). The throttle cables were synchronized by eyeball on lifting at the same time, and sometimes by transmission rattle. These methods are not good with multiple cylinder engines such as a V-6 or V-8 or inline 4, particularly those engines with more than two carburetors. The method is tricky to do with a BMW airhead boxer engine, and I do NOT recommend it. It is also NOT EVER as accurate as the vacuum nor shorting methods.

The primary method on the /2 bikes was to adjust the carburetor throttle stops for equal engine speed with first one plug cap, then the other, removed; you alternated between cylinders firing and not firing, back and forth. This was USUALLY safe on those magneto equipped /2 bikes because the magneto incorporated a safety gap, if the plug cap was pulled off the spark plug, the spark could jump across the safety gap. UNfortunately, sometimes the metal cap shell would give you an electric shock. This ‘lifting the cap’ method is still used today on the /2 bikes; although the shorting method is MUCH better.

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Carburetors

Some time ago a very embarrassed Airhead owner contacted me about how to ‘fix’ his carburetors. He has Bing CV carbs, and replaced the diaphragms, floats, etc. himself. Frankly, he is a bit ham-fisted. He also hates to ask for advice. He proceeded to nearly destroy his carburetors. The many e-mails with him prompted this article. There is a LOT of information in this article, and lots more on the author’s website. Carburetor work is not very difficult, easy to learn, and once you have worked on your carburetors, perhaps at such at an Airhead TechDay, you will wonder what all the fuss was about and you will find that it is easy the second time, and you might hardly need to refer to this article …or one of my others on carburetors…again.

I have my own ideas about when one should consider working on your Bing CV carburetors (and fuel tank and petcocks!):

YEARLY: depending on mileage and use: clean/dump float bowl contents, check corner bowl jet to be sure it is clear/open, possibly replace float bowl gasket if poor; empty gas tank, remove petcock(s), clean tank, dry it, clean petcock screen(s), possibly service petcocks internally if they are getting quite stiff to turn; or, if leaking. Inspect fuel hoses. I consider these things part of carburetor servicing. Failure to service the fuel tank will eventually be costly.

5,000 mile intervals: synchronize the carburetors, but ONLY AFTER the valve adjustment and ignition timing adjustments are checked FIRST.

30,000 mile intervals: replace float assembly (if original one piece assembly). Always also replace the float needle and clean out the central jet assembly. Replacing the float assembly is UNlikely if you have the alcohol-proof separate floats that Bing now offers. However, if you have those, be sure to replace the float needle and

{mprestriction ids=”4,5,6,8,9,10,11,12″} check the adjustment of the flimsy brass floats bridge, info on the Snowbum website in its own article on these independent float kits:
http://bmwmotorcycletech.info/bingindependent.htm

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Carburetor Rebuild Tips

“”My Bing rebuild kit arrived and I am having trouble removing the old slide needles from my 83 R100RT. Any advice on this and other Bing carb rebuild tips?””

There are two basic types of needle mountings. One type uses a captive hidden clip, and the other type has a screw that has to be loosened.

If you have to, use a pair of pliers and protect the needles with something like thin leather at the pliers jaws. BUT you might be able to remove the needles with clean and dry fingers or try soft thin leather gloves or kitchen plastic gloves. ROTATE the needle 90 degrees as you pull slightly downward, then repeat, until needle is removed. When replacing the needles, the same 90 degree rotation, with small upward pressure, is needed for each notch of needle adjustment/replacement. When done replacing the needles to what you think is the ‘correct notch’, be SURE the needles stick out of the bottom of the slides exactly the same amount…use a vernier caliper. I like to record that value. Mention of needle position is very commonly done by ‘notch’ number. The uppermost notch on the needle is

#1, and as the needle is adjusted to be higher and higher in the slide, the numbers increase, per notch, to #4.

Some needles, probably from about 1985, were made out of aluminum and the needle grooves (notches) tend to wear rather quickly. If the wear is high, that will allow the needle to be in the wrong position vertically; it can move up and down a LOT. All needles, aluminum or steel, will also wear on their sides, as does the associated needle jet. The needles are purposely free to move a bit angularly sideways, so normal vibration wears them, and their associated jet. Always replace needle and jet together when overhauling.

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