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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Engine, frame, and other numbers/characters. How to read and interpret them. How does BMW identify the year of your motorcycle, etc. Serial numbers. VIN (Vehicle Identification ‘Numbers’) & other identifications. How to identify your motorcycle and major assemblies.

This article contains a large amount of information regarding vehicle numbers and identifications, most especially for BMW Airhead motorcycles, but much of this information also applies to other motorcycles, and even your automobile, truck, etc. Information may seem confusing at first. You are advised to slowly read this entire article, and then re-read; and then look at the numbers on your own bike(s), car, truck, etc.

You may be interested in the information in: https://bmwmotorcycletech.info/models.htm and https://bmwmotorcycletech.info/transmission.htm. Those two articles have some further identification information.

There is a LOT of wordy reading here …but, it can be important!

NON-USA-SHIPPED-BIKES:
BMW may use different frame and motorcycle identification systems for non-U.S.A. motorcycles. There may be a letter or two letters, followed by a serial number. There may be a serial number followed by one extra number, and then the type of motorcycle.  Seven (7) digits are used for the serial number. I do not know what the letters nor the 8th digit means, it could be a check-digit. The VIN system of 17 characters may be absent, in favor of just the Serial Number, with possibly a very small BMW roundel stamping and a letter or two or other number or two. This has especially been seen in later Airheads for ECE shipments. In general, the 17 character VIN system was introduced in approximately 1980-1981.

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Serial/frame identification numbers, year, code, power output, from the earliest BMW motorcycles to mid-1990’s

NOTES:

(1) This article’s information was gathered from quite a number of sources, places and publications; but especially from several old factory (German literature) publications. It is believed mostly, but not absolutely correct. BMW factory literature varies in production numbers and serial numbers for quite a few models. BMW has, at times, confused…and mixed-up…their own figures. This has been particularly so when BMW has used both reserved serial numbers range for a model; and, serial numbers for actual production. BMW vehicle numbers are the serialized number of the frame or engine or both, the more modern versions of which can be 6 or 7 digits, and can be seen on the engine, and/or frame. After ~1980, the numbers are usually the last 7 digits in the new 17 character VIN numbering system, but this is not universal for all Country’s shipped-to. From 1984, BMW stopped stamping serial numbers into the area next to the engine oil dipstick. There is a LOT more to all this. See (5) below; and, see my companion article: https://bmwmotorcycletech.info/IDnumbrs.htm.

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