The Airheads Beemer Club is a non-profit club reclaiming the 'Legendary Motorcycles of Germany'
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Topic-icon New Owner Primer: Tips to Get Your Airhead Back on the Road

3 months 3 weeks ago - 3 months 2 weeks ago #4696 by Wobbly
This thread is intended to be a guide to help new Airhead owners get their bike back on the road. (This one topic is our most frequently asked question, and really as a Club, our most important duty.) Obviously, it cannot cover every detail, nor can we cover every circumstance. In this thread we're trying to point out the top 80% of recurring issues found when Airheads are brought out of storage. New owners will still need a workshop manual to explain all the details. Hopefully after reading this, a new owner will have a better idea of where to start and a higher level of confidence they are proceeding in the correct direction.

This thread is NOT for conversation. Chatter will be eliminated. If you have a question, then ask it on the appropriate forum, NOT here. If you have a helpful suggestion, then by all means feel free to contribute.

New owners should refer back to this thread, because it will continue to grow and evolve for some time.

When trying to start a new-to-you engine, the old mechanic's adage still holds true... All you need is Fuel, Fire and Compression. Typically 1 of these 3 items is completely missing, and it is always best to focus your labors on the missing item. If you seem to have all 3, then the issue moves to the next level of discovery... Is the amount of fuel correct? Is the spark at the correct time? Is the compression on all cylinders over 100 PSI ?

About 80% of motorcycles were running when placed into storage. Typically, the owner had life issues and never rode again. Almost all batteries will need replacing, but the battery typically went bad because of storage, and generally is not the reason for storage. So focus on the root Cause and don't be mislead by Symptoms.

Due to Ethanol laden fuels, in about 90% of cases the carbs will require a general cleaning. This is easy, but time-consuming work and is well within the capability of the owner-mechanic. So carbs are always a great place to start.

Don't hide 'em, Ride 'em !!
Last edit: 3 months 2 weeks ago by Wobbly.

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3 months 3 weeks ago - 3 months 2 weeks ago #4697 by Wobbly

The Airhead fuel system is simple in design and straightforward in operation. However, there are several "rubber" parts that come in contact with fuel and therefore don't age well, and then there are several other parts that will simply need inspection. And then, owing to the presence of Ethanol in US fuels, varnish and corrosion can also be an issue. All this means it is impossible to predict all the issues that might be found. We can only offer a list of items to replace, check, and clean thoroughly.

NOTE: For those new to Bing carbs, the units may appear to be identical, but they are NOT. There are numerous parts that will fit either LH or RH carb, but if they are installed in the wrong carb will create problems almost impossible to diagnose. Therefore, we HIGHLY suggest disassembling one carb at a time to preclude the mixing of parts.

Suggested parts to replace:
• All new High Octane fuel. Never trust modern fuel over 8 weeks old.
• Both rubber intake hoses
• Both float chamber floats
• Both float needles
• Both float bowl gaskets
• Both low speed jets (The smallest brass jet, typically a #45.)
• All fuel lines

Suggested parts to check:
• Both diaphragms (Check for ANY holes or rips)
• Both idle mixture screws (and blow out their passages)
• Both float bowl "enrichening jets" (See note below)
• O-rings on each jet (These can dissolve if strong carb cleaning agents are used.)
• Fuel tank petcock operation (Fuel valve packings are replaceable.)

Suggested parts to clean:
• Both float bowls (See note below)

► Check the condition of the air filter because it's critical to good carburetion. Additionally, in older models with the air intake above the starter motor, critters often build nests inside the air box and this can be a very hard issue to diagnose.

► Particular attention needs to be paid to the hidden fuel "enrichening jet", because it is almost mandatory for cold starting an Airhead. Looking inside the float bowl, you'll see a round chamber in one corner. A tiny, nearly invisible orifice at the base connects the large and small chambers. If liquid cannot pass through that orifice, then cold starting becomes nearly impossible. If your Airhead starts on 1 cylinder, then check this orifice.

► It is highly suggested that a "Top Tier" fuel be used that has built-in 'cleaners'. These are necessary to rid the tank and petcocks of built-up scum and varnish left by old fuels. If you wish to use a liquid fuel cleaner, then I can highly suggest a product called StarTron, which is both a fuel stabilizer and cleaner.

Read about it:

Don't hide 'em, Ride 'em !!
Last edit: 3 months 2 weeks ago by Wobbly.

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3 months 3 weeks ago - 3 months 2 weeks ago #4699 by Wobbly
Always get the motorcycle running with the existing ignition system. Never install a new ignition system until the bike has run at least 100 miles with the existing system.

Points Type Ignitions
► For initial startup only, we can assume the bike was running when it was put into storage, and so minimal points cleaning is all that should be needed. Clean the points where they sit without making any adjustment. A doubled-over piece of 400-600 grit emery will do, then follow that with a piece of paper to blot off any remaining debris. Check the point gap.

► After the bike is running a full service can be carried out... replacement of the auto advance springs, lubrication of the ignition cam face and auto advance mechanism, adjusting the points gap, and finally setting the ignition timing.

BMW Electronic Ignitions
The stock BMW electronic ignition is fairly robust, but there are 2 maintenance steps that should be completed on any new-to-you Airhead.

► Behind the front cover, on the front of the crankshaft, the ignition triggering device is housed in what is called "the bean can". The electrical connection to the "can" is made by a short 6" wire and a 3-position connector. If that connector is white or ivory in color, then it must be replaced. Motorrad Elecktrik can supply a replacement wire/connector assembly which is not listed on their webpage. The complete bean can is removed from the engine, and the new connector assembly added while on the workbench.

► Poor heat conduction can make the electronic control unit (located under the fuel tank) overheat and burn out. The heat sink compound between the module and the heat sink simply needs to be renewed. On dual-shock models this is located on top of the brake fluid junction. On single-shock models this is located on the RH side, in the electronics area. Separate the 2 parts, clean off the old hardened thermal compound, and replace it with a modern, high grade compound, such as Arctic Silver 5 thermal paste.

Aftermarket EI
Generally, nothing needs to be done with aftermarket electronic ignition systems. They either work or they don't.

Parts to replace
We highly suggest the replacement of several ignition parts common to ALL Airheads because the cost is very low when compared to the amount of frustration they often cause.

Suggested parts to replace:
• Both spark plugs (NGK BP7ES work well in most models.)
• Both spark plug caps (NGK 5000 Ohm ("5KΩ") work great.)
• Both spark plug wires (Wires must be metal core type wires.)

Setting the ignition timing
When setting or checking the ignition timing, it is highly suggested that a timing strobe lamp be employed, and contrary to the original instructions, the ignition timing should be set at high RPM (4000 to 5000 RPM) using the "F" mark on the flywheel. So that the flywheel's high speed mark appears in the timing hole when the ignition advance will advance no further (aka "full advance"). Accurate ignition timing is ultimately responsible for lowering the combustion temperature and the overall smoothness of the engine at speed.

Don't hide 'em, Ride 'em !!
Last edit: 3 months 2 weeks ago by Wobbly.

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3 months 3 weeks ago - 3 months 2 weeks ago #4700 by Wobbly

The Airhead engine is extremely robust and asks nothing but use of high octane fuels, regular riding, and have a regular owner maintenance schedule. With moderate care these engines can easily do 250,000 miles between major overhauls.

Valve Adjustment
It is important to note that these engines were designed for "leaded" fuels. Since those fuels are no longer available, valve clearances on most Airheads tend to close up. If the valve clearance ever gets to be zero, not only can damage to the camshaft occur, but the engine will loose compression and run very poorly. Therefore, it is imperative that valve adjustments become a regular part of the owner maintenance schedule. How fast the clearances tighten up varies from machine to machine. Your motorcycle will teach you what it likes. Start with an "every 3000 mile" routine and adjust according to what you find your machine requires.

Therefore, on any Airhead that's new to you, the first order of maintenance is to adjust the valves... then just to make sure, a second time after completing the first 100 miles.

Compression on an engine coming out of storage will typically be low. In 98% of the cases the compression will rise back to normal levels once the bike is started and ridden. New owners should resist the urge to disassemble the engine until issues persist longer than 500 miles. Compression will continue to rise over the first 5,000 miles, with the bike giving the distinct impression that it is running better with every outing. Remember, improper valve adjustment is the number 1 cause of poor compression.

There may well be oil leaks and other issues, but if possible it is much wiser to delay repair until the following winter. Then, after thousands of miles, all the issues will be fully understood, and can be corrected during a single repair.

Push rod tube seals
At the base of each chrome push rod tube (PRT) is a black, rubber seal. These make an effective oil seal by applying a slight pressure between the PRT and the engine case. After many years the combined effect of oil, fuel, UV, and engine heat will cause these 4 seals to harden and then they begin to weep oil. The only fix is PRT seal replacement, which requires a top end disassembly.

On about 95% of the bikes taken out of storage these seals will show some degree of oil leakage. However, due to the cost of BMW parts, we suggest that it is more important to place mileage on the engine and determine the viability of all the top end parts so that a full top end repair can be completed during a single disassembly. In other words, for the first several thousand miles it's far less expensive to simply keep a watchful eye on the engine oil level.

Don't hide 'em, Ride 'em !!
Last edit: 3 months 2 weeks ago by Wobbly.

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3 months 3 weeks ago - 3 months 1 week ago #4701 by Wobbly

Lubrication of the various parts is important on an Airhead. However, due to advances in lubrication and mandates by the US EPA, lubrication oils have changed significantly since your Airhead was new. Oil weights and types that were once common are now considered "specialty oils" and it may take a lot of work to locate a source for the proper oils. This is especially true of engine oils.

The Engine
Without going into details (which are covered extensively elsewhere), your Airhead engine requires an API rated oil of SF, SG, or SF/SG. Modern car oils API rated SM and SN will not adequately lubricate the Airhead engine. Sectro, Valvoline, Castrol and others still make this type oil, but it will generally not be found at mass markets like Walmart. In most areas of the country and during most weather conditions you'll want to use 20/50 or 20W50 weight oil in the engine. (I found Valvoline 20W50 VR1 "racing oil" at my local auto parts dealer with the correct API specs.)

For initial cranking of an Airhead that's been in storage, or if you simply can't locate API SF/SG oil, then you can use 15W40 diesel engine oil, API rated CJ-4, CH-4, CJ-4 or similar. The four-stroke diesel oils contain the zinc compounds the Airhead engine requires. 15W40 diesel oil also makes a great "winter grade" oil when 20W50 might be too viscous.

What I suggest for an Airhead coming out of storage, is to crank the engine and take the first rides on the less expensive 15W40 diesel oil using the existing oil filter. Then after 200-300 miles you can drain the diesel oil and install the SF/SG 20W50 oil, along with a new engine oil filter.

(Note: Before changing the engine oil filter read and understand the information at the bottom of this page.)

Gearbox, driveshaft and final drive
These 3 oil reservoirs can benefit from advances in gear oil lubrication. While your original manual may suggest 90W gear lube, most gear lubes these days are multi-grade oils, such as 75/140, in either regular mineral based or full synthetic. Experiment and see what your machine likes. Most new gear oils far exceed the original BMW requirements.

Front forks (shocks)
No other oil is as important to good handling (and therefore your safety) or as over-looked as the front fork oil. Clean and equal amounts of fork oil help keep the bike going where you intend. Generally, any high grade of "fork oil" between 7 weight and 10 will work. And the oil weight can be varied within that range to obtain the ride characteristics you desire.

Rear shock(s)
The OEM rear shock(s) are sealed units and cannot be serviced. The maximum life of the rear shock(s) is 5-7 years.

Swing arm
The swing arm bearings are lubricated independently from each side. Access is gained by popping off the plastic cover caps. A special "needle nozzle" is required to get the grease onto the bearings. Grease is an important part of excluding water and dirt from the swing arm bearings.

Wheel bearings
At some point you will want to make sure the wheel bearings are properly lubricated. Wheel bearing maintenance isn't needed very often, but when overlooked can result in dangerous handling. So it's best to check and be safe.

Head post bearings
The forks turn on tapered roller bearings which need their lubricant replaced every 10 years or so. It is common to feel a grittiness or "hunting" within the steering bearings due to the presence of old, oxidized grease. If there is no rust on the bearings, then the old, solidified grease simply needs to be washed out and renewed. This can be done by dropping the front forks 6" and washing the bearings in place.

Proper steering directly depends upon the fork bearings having zero resistance to turning, while at the same time having zero "free play" in the bearings. It's a delicate adjustment that requires some pre-loading of the head post bearings and the proper water-resistant grease. Consult your shop manual.

Engine oil filter
There are several things you need to understand before attempting to change the Airhead engine oil filter. The 2 main ones are:
► Airhead engine oil filters take at least 3 different physical forms. They are not interchangeable, but to the untrained eye they can look nearly identical. You must use the filter that is correct for your model or engine damage can result. The biggest difference is that engines with an oil cooler use a different filter from the non-cooler models.

Secondly, for /6 and later machines the fitting of the white o-ring is critical to engine lubrication. This o-ring has been called the "$2000 o-ring" and it's proper fitting should be thoroughly researched BEFORE attempting to change the engine oil filter. If you are not sure of how this o-ring fit is properly measured and installed, then it is much safer for the engine NOT to change the oil filter until you do understand it.

Read about it: (Snowbum's article on the white o-ring)

Don't hide 'em, Ride 'em !!
Last edit: 3 months 1 week ago by Wobbly.

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3 months 3 weeks ago - 3 months 2 weeks ago #4711 by Wobbly

Wheels, tires and brakes are items which need a thorough safety check before you hit the road on your new-to-you Airhead.

Due to their multiple failure modes, tires older than 5 years generally shouldn't be trusted. Since the mid-1970's tires sold in the US have a molded-in date code, which typically consists of the last 2 digits of the year. This code typically appears on only one sidewall. For example, if you see "98", that tire was made in 1998.

There are many great tires available for these vintage rim sizes. The least expensive, most basic tire I advise using on Airheads is the Bridgestone S11 "Spitfire". There are also great European tires from Michelin, Continental, Metzler, and Heidenaur.

► It is also good to note that modern tires need about 6psi higher inflation than the pressures listed in most of the original owners and shop manuals. I'm running 36psi front, and 34psi rear on an R100 RS.

Inner tubes
If you replace an old tire, then replace the old inner tube. Inner tubes with patches should always be replaced. Inner tubes move inside the tire during use, so a light coating of talc can act as a "lubricant".

Mechanical drum brakes
These brakes typically collect a minor coating of rust, which makes them extra "grabby". No disassembly is generally needed, just apply them over and over within the first several miles of riding to knock off the rust and bring them back to life. Some minor adjustment may be required since the rust accelerates wear during that period.

Hydraulic disc brakes
Hydraulic disc brakes do not age well and can require quite extensive work to restore them to a safe working condition. For your safety, full attention should be given to the complete hydraulic system before the bike is ridden.

• BMW advises annual brake fluid replacement, because due to water absorption, the useful life of DOT4 brake fluid is very short. Therefore you'll need to do a complete brake fluid flush and replacement before any riding. On a /6 or /7 bike with the brake master cylinder under the fuel tank, this action can be quite labor intensive.

NOTE: DOT4 brake fluid is highly corrosive and will eat the paint off any surface it remains on. It is always best to end every hydraulic brake repair session with a gentle washing using hot, soapy water. This is especially true of fuel tanks, fairings, and frames.

• OEM flexible brake hoses are known to fail internally and completely block the flow of brake fluid. It is highly advisable to replace all OEM flexible hoses with "stainless steel" versions at your first opportunity. These are available from multiple sources. One trusted source is Speigler. These new style brake hoses will almost double your braking efficiency.

• Brake pads have evolved significantly in the last 20 years. It is highly advisable to replace any older pads with modern brake pads from EBC. Again, improved braking is a good thing.

Wheel bearings
Lubrication of the wheel bearings was covered under Lubrication.

Read about it:

Don't hide 'em, Ride 'em !!
Last edit: 3 months 2 weeks ago by Wobbly.

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