1979 BMW R100RS complete redo: "Shiny Crumpet"

I have mainly been a lurker on this forum, but have enjoyed practically every Cafe Racer Thread on here. Some of the builds are way beyond my expertise, but I figure it is time to post my build on a previously Cafe'd 79 BMW R100RS. From the factory, the RS would have had a large fairing section and be set up perfectly for touring. My bike, purchased from ebay UK, had already gone through a pretty extensive transformation to cafe racer. It had, and still has, very few BMW body parts. A picture, then a better explanation:

This is one of the pics on ebay:


Tank is a Terry Baker tank, rear cowl and fender is caferace.com, front forks are from a later /7, 81-84, handlebars are multi adjustable, but the wheels are stock color. Yes, folks, the wheels were gold from the factory. I loved the way this bike looked right off. Unfortunately, execution was not as good as you might believe. The tank is NOT for a BMW. Actually, it was not secured in any way. It sat on a foam roll on the backbone of the frame and was generally smashed forward by the seat. When you rode, it rattled and hit the steering stock. It was a mess!!



Too bad, because it is beautiful. I later gave it some polishing, and it only got better and better as I polished it.

My guess now is that the bike was built a few years ago, probably 5 or more, and then driven, hard, and put away wet, alot. It had many nice parts, but every seal was tired, and every surface was gross. Front forks were leaking, rear main seal was leaking, final drive leaked from every orifice. Push rod tubes leaked, meaning everything below them was coated with a combination of road grime and oil. Nothing was dry. You could glance at the bike as you passed by it in the garage and you would get dirty.

Anything not well coated or made of stainless was rusty. Actually, the headers are stainless, and they were super corroded also due to the heat cycles. Shocks = ugly, Exhaust cans = Unsaveable. Thankfully, frame and subframe looked good and had most of their original paint intact.

With most, but not all, of the complaining complete, the good things: Started well, has plenty of power, doesn't smoke, and has good tires.

I have a decently extensive tear down thread already in advrider, but am starting to get where I will want the expertise and honesty and opinions about where to go with the body work and paint. I am 50% through this project already, and am going to post condensed versions of the teardown here. Advrider is full of BMW guys with beautiful bikes, and I am afraid my build is just not conventional enough to get much interest.

Let the build begin!!

Pre-Teardown:



And with a few deletions and additions:

Start of the condensed teardown

I won't start with 20 detailed pictures of how it looked, I will just get right into the work. The battery was located on top of the transmission, where the stock airbox used to be, so I made and welded on some bracket to the rear subframe and mounted the odyssey battery under the cowl. I know that many people do not like the location under the cowl, but the odyssey is pretty light. This required removal of the aftermarket aluminum fender. Later, I cut and polished the fender and used it as a small deflector between the rear wheel and the engine.

Battery location before:


New Tabs and shortened battery box:



Be kind about the welds. I am using a flux core MIG welder, 110V, through a 2000W transformer. As I am in Italy working for the Military, I spend too much time using a transformer in my garage to run my tools. I am still amazed that the welder will work with the transformer. My air compressor certainly doesn't like it!!

I also started ordering parts and cleaning parts. As mentioned above, nothing was able to be handled. The front engine cover was painted black, so I spent some time with aircraft stripper and red scotchbright. Crappy job. If I knew the blaster I know now, I would never have done that job by hand.





Cleaning up starter cover:



And failed to clean up the exhaust. The rust was too bad.



Remember the "gas tank mounting system"?

Swingarms and exhaust headers

Let's talk swingarms:

Originally, on my 79, it used the a dual sided swingarm with a necked down portion on the driveshaft side. In 81, BMW changed the design, and significantly increased the size of the driveshaft tube. This made a large improvement to the handling by reducing the amount that the swingarm flexed during cornering. Thus, the wheel stayed more in line with the bike. It is easy to see the difference:



I bought a later style swingarm and driveshaft from ebay, and am fitting them to my bike. The driveshaft is also different. Maybe not better, but different, in that it uses a spring to create a "cush" effect rather than the original straight driveshaft. It will be interesting to see if I can feel the difference. I did notice during my riding after purchase that the bike was much more sensitive to rev matching and the rear wheel locking up during clutch transitions that any other bike I had written.

The exhaust pipes needed attention. Alot of attention. With sandpaper and steel wool and a buffing wheel. But multiple grade sanding and lots of buffing finally yielded great results.

After and Before:


and with new cans from dimecity, the exhaust looks brand new:

Awesome, man. I am on board.

I'll be watching this one having built 3 Cafe Racer Airheads in the past [ 2 x R80, 1 x R100 ].
The problem I faced, was that there's no a lot you can do to make them different ! Apart from the details of course.

Never understood the gnashing of teeth when you suggest putting a 4 kgs battery under the seat bump. Unless you weigh under 60 kgs - it makes no bloody difference at all ! Most of your own body weight is way above the COG to start with. I used a Triumph Metisse tank on 2 of mine and various Duke 750SS ans AJS 7R seats. Alloy rimmed wheels / stainless spokes, etc.,etc.

I left the main UK BMW club as their holyer than thou attitude to anything other than a stock Beemer made me want to puke.

My final Airhead fling will be a Max Deubel sitter sidecar homage.

There's something "right" about an Airhead Cafe Racer - power to you.

Slippery Slope

At this point, I fell into a hole and started taking leaky things apart. And I still haven't recovered.

First, the leaky final drive:



Inside of rear wheel:


This led to the removal and complete teardown in order to replace the main seal:



Then I removed the transmission. This was mainly to repair a broken flange at the outlet of the transmission. The bike had some signs of a hard fall at some points, like a bent peg, and I believe the jolt put a lot of stress on the end cover of the transmission and cracked it in multiple spots. I explored repairing the cover, but one of the inside bearing races was also cracked, which precluded repairs.



I bought a used cover on ebay and also checked the bearing inside. They were tight, so I just replaced all of the seals in the transmission.



While the transmission was out, I removed the clutch assembly and flywheel to investigate a nasty amount of oil inside the bellhousing. I have many theories of it's origins, but I cleaned it up and replaced every seal just to be safe. Many have commented that it was the nastiest they had ever seen one of these engines.





I wasn't near out of the hole yet though. It had just begun.

Beach, if your builds are posted here, I am sure I have read them, but I don't remember any with that many mods. Pics?

I agree though that they are hard to mod but I also think they are easy to mod. Practically all the parts from 70-84 fit on every bike, including the tank, seats, fenders, etc. Ofcourse they are not all just straight fits, but I love all the different tanks you can use with no mods. The other huge benefit is the availability of parts. They may be expensive, but you can order EVERYTHING. My past ownership of old Yamahas made me think that most old bikes were destined for used parts.

BTW, I think I lost most of the BMW guys when I mentioned a blue frame. You can have it any color you like as long as it is black. They are AWESOME for technical questions though. Those guys have seen everything because most are real riders.

Gotta have a picture. How bout a helper?

A boxer to help with your boxer?

Front fender

One more post for the day. As mentioned before, the forks on this bike are later type, 81-84, and have dual Brembo calipers rather than ATE. My bike also has the handlebar mounted master cylinder. The PO had obviously changed the fork lowers but not used a later style fork brace. The holes for the brace are a different orientation on the earlier style, so the fender ended up having a huge gap in the front.


I fixed this by picking up a later brace and a matched fender from an 83 RSon ebay. I still haven't cut down the fender, so I think it is too long, but the fit is perfect.



You might also notice that I removed the paint from the front forks. I want them to match the polished shocks.

veloracermike said:

A boxer to help with your boxer?

Click to expand...

He would be much more help if he wasn't trying to either lick my face off or lean on me with all his weight!! But he's the best. His name is Doc Brown. Probably doesn't surprise you that the cat's name is Marty.

xavier296 said:

Beach, if your builds are posted here, I am sure I have read them, but I don't remember any with that many mods. Pics?

I agree though that they are hard to mod but I also think they are easy to mod. Practically all the parts from 70-84 fit on every bike, including the tank, seats, fenders, etc. Ofcourse they are not all just straight fits, but I love all the different tanks you can use with no mods. The other huge benefit is the availability of parts. They may be expensive, but you can order EVERYTHING. My past ownership of old Yamahas made me think that most old bikes were destined for used parts.

BTW, I think I lost most of the BMW guys when I mentioned a blue frame. You can have it any color you like as long as it is black. They are AWESOME for technical questions though. Those guys have seen everything because most are real riders.

Gotta have a picture. How bout a helper?

Click to expand...

Xavier, they were all built in pre- Forum , pre-Internet days - however I'll see if I can find some old pix in the loft !

NIce work.

Teardown

I had originally hoped that I could add all of the new parts, change the seals, then drive the old girl for awhile before I did the full strip down and clean up. This didn't happen though, as the inevitable waiting for parts leads to boredom, and with a half apart bike just sitting there, it is too easy to want to bring her all the way down.



See? You would want to finish it up also, so about an hour later, she was here:



With the engine on the ground, I then removed the two engine studs and pulled the frame off the motor.

I am getting a pretty significant amount of items powdercoated, so I started working on fixing or modifying those parts which needed it. The centerstand is a huge wear item obviously, as it touched the ground constantly and takes the weight of the bike. Mine was super thin and dented on one side and had a hole on the other.

The good side:


So, with my limited MIG experience, I added metal. Alot of metal. And then ground it down to follow the curve. It isn't pretty, but you will not be able to see it and the bike should come up on to the stand much better now.



I also added a cut off wrench as the little extension to push down the center stand prior to putting it up. The stock ones are notorious for breaking off. If this one breaks, it will be the weld and not the wrench. I tried to bend the wrench alittle with a large wrench and lots of heat, and it didn't budge even a mm. I guess drop forged old wrenches are pretty tough.

It looks like I added way too much weld, but I just welded over the original weld for the stock pushdown.



So, with a little more cleanup of holes and scratches and unneeded tabs (I spent hours on the frame with a file and sandpaper. Fun work), parts go to powdercoater (some to be powdered, some to be polished, some to be zinced):




When I dropped this batch off, I picked up the first batch of black. This is rear subframe, battery box, swingarm, and a couple other brackets.

With the motor out, I did some soda blasting:



It was my intention to just clean up the block itself, and found that while the soda blasting doesn't make the block "perfect," it does make a huge improvement and also helps get rid of the problem that my hands get dirty when I even look at the engine. Ohh, shiny:



It did not, however, magically make my hacked up charging system look any better. The stator is rough, while I was surprised to find the rotor looks new.




I also removed the cylinders. They are being looked at, along with the heads/valves, by a local shop.





There isn't going to be anything about this bike that I haven't had my fingers in. Should make maintenance tasks easier later!

X-296 I would grind the 5/16" wrench so it would open a beer bottle? At the picture of the stator you have a small banner in the background, Cavalino ramparte. Do you have one?
Cheers, 50gary

Back from powdercoat

I love the beer opener idea, but I already got the center stand back from powdercoat. It might work anyway, I'll go check.

So, lots of parts back from the powder coating shop, including frame and wheels. The blue of the frame and wheels just can't decide what color it is. The flash makes it look very light, while it is actually pretty dark. They had 3 blue colors in stock, and this one matched perfectly to my idea. It was the same color as on a set of running shoes I have.

His rack fits completely in the oven. It can hold an entire car frame.





Valve covers:



Frame:


A bunch of zinced parts, both shiny and black zinc:

Engine shop

When I went with my friend Ciro to the engine shop to check the heads and bores, he showed me his bikes there getting built.

All the way down Norton Commando 750:


One of Two Benelli Tornado 650s:



Other random Italian bikes in the shop:




Not great news from the engine guy though. Heads need all new guides and two new valves. Pistons need new rings. 42k miles on the speedo. Maybe that is about right.

The valve guides notoriously go bad on the bimmers, but the new ones they put in are much better quality. You'll be glad you did it. Love the blue.

I LOVE what you're doing! I've always wanted to do a Beemer, yours will serve as a great example!

Nice BMW love the tank, you had posted on my build you were thinking about doing your frame sliver. I came across this bike on the fourm. Thought I'd pass it to you.
http://www.dotheton.com/forum/index.php?topic=13652.0