I have a ’78 R100/7. It’s my first BMW. It broke down a few weeks ago and I never got it started again. The problem is I have no spark. The local shop is no help unless you bring the bike in and I don’t trust them. I don’t think it would be a coil because there’s no spark on either side.
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.
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).
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:
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.
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.
The main seal at the back of the R100 motor is large (more than three inches on the outside diameter) and narrow, making installation a challenge without the proper tool. When removing the transmission for a main shaft circlip upgrade, I noticed that the main seal that I’d installed with a drift and hammer was leaking between the engine case and the OD of the seal. More than likely this was do to bending the seal body with the drift, since it’s almost impossible to keep the seal square to the bore all the way around using that method. While I was at Ted Porter’s BMW shop I noticed a main seal installation tool laying on his bench, and asked if I could copy some dimensions from it. Ted readily agreed, and even offered to read the dimensions off as I wrote them down. Unfortunately, his eyeballs are as bad as mine, and it took both of us to read the caliper! Regardless, on my return home I sat down at the computer and knocked out a drawing, simplified from the driver on Ted’s bench to make fabrication in my small shop a bit easier. You can jump to a larger version by clicking on the thumbnail.
Everyone has things they swear by, and sealants for engines seems to be one of them. Back in my Norton days I gave up on Hylomar because I found it would only remain leak free for a few thousand miles. One of my buddies mentioned that his Yamaha dealer used some stuff called Yamabond to keep the oil in his two stroke dirt bike, and I figured if it could keep that motor dry it was worth a try for the Nortons. It was, and it worked very well. When I started working on Airhead BMWs it was only natural to continue using Yamabond (now a days called Three Bond 1209), and it continued to work well. Right up until the day I pulled a cylinder for a compression bump upgrade and found ThreeBond almost blocking the oil passages leading up to the valve gear. Clearly I’d used way too much of a good thing and almost caused me a bunch of trouble in the process. So when the Gurus on the Airheads mailing list recommended Hylomar because if too much was used the extra would float harmlessly away in the oil, it made sense and I started using it again. Of course my old tube from the 1980’s was dry, but since those days Permatex started carrying it and a quick trip down to Kragen’s and I was back in business. However, it seems Permatex is no longer distributing Hylomar, and while my tube should last me another ten years, there are other Gurus that contend, as I had found with the Nortons, that the Hylomar would not provide a good cylinder base seal over the long run. And these guys recommend the Permatex equivalent of ThreeBond 1209, a silicon based sealant.
One of these Gurus is Ted Porter, principal of The Beemer Shop in Scotts Valley, California. I visited Ted one misty January afternoon to drop off a transmission for a mainshaft circlip installation, and during the course of our conversation I mentioned the Airheads sealant thread. He offered to show me how he uses the silicon based sealants.Continue readingMore Tag
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!
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.
(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.