Oil Coolers

Why an oil cooler?

Air cooled motorcycles can run quite hot in some situations. This includes large amounts of throttle power for long periods of time; pulling a trailer or sidecar where a lot of engine power is needed; extremely bad traffic conditions; use of fairings in general (particularly fairing lower center pieces that are not ventilated). Engine cooling is obviously worse in quite hot weather. Your BMW Airhead engine has more than enough cylinder fins & head fins to dissipate enough engine heat in most circumstances, including some fairly extensive stop & go traffic, & modest speeds pulling a trailer or sidecar. But, there are limits.

For proper engine operation, lubrication, protection, etc., engine oil should operate in a reasonable temperature range after the engine has warmed up; not too cold, not too hot. The oil also needs proper viscosity over its expected temperature range in the engine. Usually, a multi-grade oil such as 20W50 is used in our Airheads. Quality 20W50 motorcycle oil is far better than the old single grades type of oils, & is quite adequate for most conditions, but a thinner oil might be wise if temperatures are at or below freezing; perhaps a 10W40. 10W50 and 15W50 oils are also available.

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Oil and Filter Changes, Procedures, Technical Information, and the $2000 O-Ring

Your /5 and later BMW Airhead motorcycle has a well-deserved reputation for reliability and exceptionally long life.  Regular oil and filter changes based on both time and mileage are necessary.  Use of a quality oil and quality oil filter is highly recommended.  There have been quite a few different filter numbers, filter styles, and methods of fitting them and associated parts such as O-rings, gaskets, shims, and oil cooler attachments, over the years of Airhead production.  This article will attempt to cover all versions,  models,  situations.  HOWEVER, the Author’s website has several articles, number 49 through 51D, THAT SHOULD BE READ; these cover things in more depth; things you REALLY NEED to know.  Please be sure to read all those articles.

Failure to follow recommended procedures, particularly on /7 and later models, or any model with an oil cooler, can result in $$$ repairs. There is a critical white round large rubber O-ring used on the outer cover on models with oil coolers, and also used on later models without coolers. That O-ring must be in good condition, and under proper mechanical mounting pressure, in the proper way. A failure here can result in an engine rebuild costing at least $2000; and if the crankshaft failed, perhaps over $3500. Reading articles 49-51D on the author’s website AND the entire article you are reading will make you an INFORMED owner, highly unlikely to make an expensive mistake…or allow someone else to make such a mistake.    

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Double Row Timing Chains for Dummies

YOU CAN DO IT. You will want to replace everything. Don’t do a rinky dink job that will need to be redone sooner rather than later. Replace the chain $35, crankshaft nose bearing $10 and sprocket $65. Also replace the tensioner $10 and spring $2, and all gaskets and seals $17. These are 2003 prices. I got everything from Motobins and Eurotech. I found that the most worn piece was the crankshaft sprocket. The chain and bearing actually do not wear that much, but that sprocket is half the size of the cam sprocket and made of some soft stuff. The teeth get narrow and pointy. The gap between the teeth gets really wide as the sprocket wears. That’s where most of the slop in the old chain comes from.

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Cylinders, case stud threads, heads, top-end, intake spigots, break-in procedures

If you are installing a camshaft and/or followers, READ http://bmwmotorcycletech.info/cams.htm regarding assembly pre-lubrication.

You may think that pulling off a jug is major surgery & frightening to contemplate. Once you do it, perhaps at a TechDay; or, from the information in this article, you should no longer have much apprehension about doing it yourself.

CAUTION-1:  Every year comes questions about removing a head, perhaps for a simple de-coking (and not pushrod tube seals), & whether it is possible or not….to keep the cylinder sealed at the bottom. In order to do this, you would have to very securely wrap bungees …or via some other means, …around the cylinder fins, across the motor, & all-around the motor. Or some such. You would have to keep the cylinders from moving off the base area in the slightest. This method has been done when I only needed to work on the heads & was being done ‘in the field’, such as at a Rally, or a TechDay, & no O-rings and no piston ring compressor were on hand, etc.  But,  in order to do it, the bungees must be super-tight & evenly surrounding the cylinder, fore & aft. I recommend you not try it. Chances are high that you will not be fully successful & your cylinders will leak oil.

CAUTION-2:  Never reuse a head gasket unless it is a real emergency. While it is possible to leave the two head-to-barrel nuts in place (the ones located at 12:00 and 6:00), & to reuse the gasket by never separating the head from the barrel, this is a poor idea. It MIGHT result in distortion of the assembly. I have not seen that distortion, if the assembly is done fairly quickly, within minutes. Pure speculation anyway. These 2 head nuts (located at 12:00 & 6:00) are supposed to be the first to be loosened, the last to be tightened (in the usual cross-staging).  

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Cylinders (iron, steel, Nikasil, Galnikal). Boring, honing, cylinder shims, plates, gaskets, o-rings.

BMW has used both Galnikal & Nikasil in describing their late cylinders, & never explained the difference. BMW used at least two companies in producing these cylinders for them. They are basically the same process.  Nikasil is a registered trademark of Mahle Gesellshaft (yes, the piston and filter makers). Coated cylinders are done via a plasma process, in Stuttgart, & is a blend of nickel & silicon carbide. Galnikal is a trademarked name for the process used by Kolben Schmidt, which is a major German foundry & castings maker. They also make pistons. If you have Kolben Schmidt cylinders, or other products, they use a symbol which is a letter “K” on top of a letter “S”, and it looks like this:

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Changing a Timing Chain

Getting started: I, having done this a number of times, budget about three to four hours to do this task. I’ve done it in two hours with everything going well. Sometimes you find the exhaust nuts are frozen on. Sometimes the universe is just not going to let you get that keeper/clip on the timing chain until you have REALLY demonstrated you want it. And so on. First time? Four hours: minimum. I would place this in the “advanced intermediate” catagory of dificulty.

Change oil if it is nearing that time. Turn engine to Top-Dead-Center. You have to clear away obstructing parts first: namely the front wheel, fender and exhasut system. Drop the exhaust pipes and headers, pull the front wheel and remove the fender/lower sliders, after draining fork oil (now might be a great time to do fork seals too…). It helps to have the bike on the center stand and a couple of 2X4s to get the front end up. Now remove the tank, disconnect the battery ground cable, loosen the carbs and remove the air cleaner assembly. Remove the starter motor cover, this is the cast aluminium piece on top of the engine block, you may have to undo the coils and move them out of the way to accomplish this.

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Camshafts, broken cam tips, cam sprockets, lifters (followers), alternator & cam seals, crank nose bearing, etc. Sports-cams installations. Assembly lubricants.

STOCK, original equipment camshafts:

For the stock cams, at .0787″ valve lift (2 mm), the timings are as follows, keep in mind that two types of these cams installation available, the 3° advanced one & the not advanced one.

R50/5, R60/5, and R60/6 to 1975:
BMW issued a SI on that camshaft, saying that some published information was NOT correct. BMW said the correct figures are:
Intake Opens TDC; Intake Closes 40° ABDC; Exhaust Opens 40° BBDC; Ex Closes was illegible, but I am sure it said 40° BTDC. If you were to look up the sprocket and camshaft in the present parts fiche, it would be 11-31-1-250-253, sprocket.
284° camshaft, used UP TO 09/1975, 11-31-1-259-262.

UNfortunately, BMW is confusing itself. You will find that other manuals say Intake Opens 40°ATDC….all the numbers are 40°; that includes the intake opening at 40° ATDC.

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