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Cafe-Fighter? any interest in this BMW build

13K views 78 replies 20 participants last post by  Diggler440 
#1 ·
Update: 8/20/2014 took it on the first ride to the gas station and I mad it about 2 miles before the carnage happened. It came home on a tow truck but the place I coasted into made for some nice pictures











The carnage was the driveshaft bolts were loose (one of the few things I never disassembled and therefore never checked). The driveshaft came loose at about 60 mph and destroyed the flange on the transmission the boot clamps to. I will need a new rear trans case, FML















I began building this Airhead a while ago. it is a 1981 R100RT with 8" out of the tail and numerous other modifications. I type slow and I have copious pics of the build thus far

Any interest?

I went from this:






to this:







to this:





 
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18
#7 ·
The world can never have enough chopped up bmw's...
Post on man...
 
#9 ·
Here is the cliff notes:

I was given an 1981 R100RT that was severely neglected and pretty rough. The layer of of oxidization ad rust were pretty deep so I dont feel sad at all for what I did to it in this thread. It was given to me by a friend of my parents, at first I just left it to sit in a corner of the garage wondering what I was going to do with it. I could not sell it as that was part of the "gift conditions" so it sat and sat and sat. I rode it once up the driveway after I got it. It ran which is about all I can say that is nice. The brakes were bad, both masters leaked fluid as fast as you could add it. The exhaust was falling apart, it was ugly, and there is a ton of slop in the rear end as the splines are toast.

So a little about me, I come from a 2 wheeled family my dad puts more miles on his Tiger than I do in my daily cage. My mom has a Triumph Legend side-hack that she motors about.

I think there might have been a very brief time in my late teens that some sort of gyro balanced motor transportation was not in my life (but that time was long ago and is fuzzy to say the least).

So in 2011 I was working managing an automotive shop where I had been for 13 years. I hated my job, I had been hired to change oil and sweep floors but throughout the years I somehow ended up in the office writing work orders and running the shop. I was much happier back in my bay doing diagnosis and building cool stuff, (which I am aggressively mediocre at ). The shop fixed your everyday mundane vehicle issues but we also built hotrods, mostly Model A's but there were many others to mix it up. Prior to being the head lackey I had a good gig I was an ASE master with L1, X1, and (the newer) A9 certs. I did all the custom fab work and a few of our cars ended up in magazines ( American Rodder inside cover and a nice write up).

Did I mention I hated my job? Not just hated it but loathed every minute I spent there. I would come home a ball of stress turning me into a shitty father and a shitty husband. So I decided to drastically change careers, which I did. When I quit I hated working on things with motors just as an extension of of unhappiness in my career. I brought my tools and equipment home and packed them into my garage not even so much as changing oil for quite a while.

It took months but in May 2012 I saw that poor old RT sitting in the corner and a lightbulb went off. I was working nightshift in my new career and I had a ton of time to myself, so rather than drink and watch netflix I put it on the lift and started this journey. I quickly remembered what I loved about building mechanical stuff and I could do it in a leisurely manner and whilst drinking beer.

I tend to lean toward sportbikes (my elderly Kawi is in some of the pictures) so this hack I am shooting for a cafe-esque look but with some modern influences. If you can picture an Airhead, a Norton Manx, and a Triumph Speed Triple getting wasted and having an inter-species orgy, the illegitimate bastard that came of that union is what I am looking to create.

So with that said welcome to my therapy.
 
#10 ·
So here is where it all started I got the bike up on the lift and started looking. I knew that I wanted to go cafe-ish but I also knew I needed to strip the poor old beast prior to any hacking


















So now the big pieces start to come off starting at the back and moving forward










Once the fairing was off I put the tail back on to look. Now I am old enough to have had Sir Mix-a-Lot on cassette (now on my iPod) and while I agree with his proclamation of love for large round backsides this was too much Ghetto Booty, that ass is huge. Red beans and rice dont miss her...




I knew I was going to bob that tail when I started so I needed to get down to the seatpan








After putting the seatpan back on I measured that I could lop 8 inches out of the middle to get the look I desired but because I was bobbing the seat I had to bob the frame too









 
#11 ·
Now that the frame was bobbed I could get to the tail and seatpan. I have to mention that before the big snowball I was going to use the factory seat hinges and mounting so it would still lift and pivot as it was designed to do.

rusty and dirty





needs some patchin



Here to being 8 inches short (I'm irish yall, I'm used to it)













the tail is now ready to be cut to match the seatpan








Oh TIG welder how I love thee







and here is the tail mounted up looking much better than the ghetto bootied start












But I still have the rusty seatpan to deal with, in the below photos I joined the sections, patched the rusty hole, and installed new metric Nutserts to attach the tail















Done and painted


 
#12 ·
I wanted the tail to have a cleaner look so I stared at it for a while, had a couple beers and got this bright idea to pinch the subframe supports inward to the battery box mount leaving room on the outside to lay down the shocks I figured I would just make some new shock mounts and leave the subframe pretty much factory (with the exception of the pinched support bars)









With this idea the snowball began to roll I ordered a pair of external reservoir off ebay that were just a bit longer than the factory ones. but once I got them I found that my idea of pinching the subframe supports didnt pencil out like I thought,so the cutting and chopping began in earnest. I distinctly remember putting the recip saw to the subframe mounting tab and asking myself if I was making a good decision so I had a beer and ignored the stupid naysaying voice.



enough dumpage for now, to be continued......
 
#13 ·
This is where the whole project changed, I had purchased the longer shocks and had found they would not work with the pinched subframe support idea. So I got out the recip saw and cut of the subframe mounting tabs. Once the tabs were cut off I had some rather ugly growths that needed to be smoothed












Now to build a new subframe, I used threaded rod bolted through the battery box holes in order to be able to adjust the seatpan and tail to the correct height and angle prior to tacking together a subframe. It worked pretty well and I used a 3rd bolt on the tire to get the rear at the correct height.







And now the shock mounts need built so I had a beer and l stared for a while. My first thought was to make the shock mounts support the seat. so I mocked up a bracket from card board.









And I got ready to make some cuts






Flame cutting is ok but I really need a plasma torch









Since I had flamecut ala freehand the brackets they needed some work to look respectable so I clamped them together for some judicious grinding and shaping







After shaping them I have 4 brackets that look exactly like each other and match the template I had made





 
#14 ·
Now to drill the holes the shocks will bolt through


[/URL



Everyone has a supervisor and mine says he is not convinced that the shock mounts I am making will look good. He said some other stuff too but it was mostly about Batman and Lightning McQueen.


[URL=https://imageshack.com/i/nrdscf0598qj]



Once I got the hole drilled and the mounts bolted to the shock I had to form the mounts to match the curvature of the frame.








And this is where I end up not happy I really should have listened to my supervisor as he has an eye for aesthetics. With the mounts formed and the tail in place on top of them it looked clunky and like an afterthought. The mounts did not flow with the shape of the tail or the frame. So I sat in my rocking chair, had a beer, and cried while staring at the damn thing. My supervisor would have my ass if I screwed this up, so I continued to cipher until I had a better idea.








Ok I got done with my man tears and asked myself what kind of look I liked in bikes that I could apply here. And the answer I came up with was a Ducati steel trellis frame. While that is not what I built, I wanted something that would be simple, lithe and strong. I didnt tell the supervisor but I started to build shock mount pockets that I figured I would weld to the frame with triangulated tubes.

As always I made a pattern and beer helped me get started




The old shock mounts were good for something





Once I had the rough cut I shaped them the same way I did the old shock mounts and got ready to tack it together








I started my tacks at the top of the semi-circle and closed it up with the vice before I finished welding








 
#15 ·
With the shock pockets done I began to build the seat mount, I used M/S tubing, chamfered the edges in the lathe and istalled nutserts in the end to hang..... .....stuff













I welded a spreader support onto the frame and tacked together the seat mount in the vise








Then I tacked the frame to the spreader







I cut two small spacers and clamped the shock pockets to the seat frame and tacked it into place.







This looks a little better the Supervisor will be pleased





I used pieces of the old subframe to make the triangulated shock pocket braces that will bear the brunt of the working load against the frame. I also added a second set of triangulated braces to the spreader between the two shock pockets. I moved the location of the shock pockets to lower the rear 1.75 inches for the short and wide look (kinda like me).














When I finished the seat rested on the factory rubber buttons on top of the seat frame. This look both myself and the supervisor are more pleased with.






Because I lowered the rear I also needed to lower the front the same amount to keep the correct geometry and look. So some shiny new parts were ordered. I am really trying to build everything I can on this, but for $120.00 the San Jose triple clamp was well worth the money spent. Besides a machinist I am not








Next up.... exhaust



To be continued
 
#18 ·
I was getting to the point in his project where I needed to drop some cash (that I did not have BTW) because I started pricing DOM tubing and just could not pry it out of my wallet.

I saw these in the far back reaches of my shop and they had been taking up room forever. I tried to Craigslist them for 50.00 each but there was not even one response, Both were 1 5/8 tubes 1 set was new for small block chevy truck and the other set was used but still in excellent shape for a 2nd gen 455 Pontiac F-body. All those sexy mandrel bends....





All those seck-say mandrel bends in a pile I could pick from







I cut off the factory pipes 2 inches in front of the nuts and started on the left side first. I routed it to the right side and left room to get the oil filter out.










At this point the pipes are within 1/2 inch of each other 26.5 and 27 inches




Now I start adding on, raising the level as I plan to go under the swingarm and behind the transmission






Now that I am at the "bend in the road" so to speak I get input from my supervisor who confirms my doubts about the right side pipe being too low and not looking just right. However in the spirit of creative influence he says to continue and I can fix the pipe later










Now I have to go under the trans and the ultimate goal is to exit under the tail with no mufflers. Would you believe me if I said "loud pipe save lives", I thought not. I cannot even believe I typed that lame ass screaming eagle horse shit. I dont want mufflers because it will efff with the look and flow of the bike. I will lose some ( a lot) of low end but I am not building this for the Iron-Butt or Paris to Dakar. Besides, I can make some of it up in rear-end gearing


Not only do I have to make a 90 degree bend but I have to megre 2 into 1 to balance the system but I also want to have the look of dual pipes. So I start by building a 2 into 2 "X" pipe with a small choked area about 2 1/8 inches ID

gotta have a merge collector to that and I had four laying about I cut from the headers. So I put them in the band saw








I got 2 90's and expanded the ends so I could use band clamps to seal them and tacked them into the merge I also used a piece of 2 inch stainless as a form so the outlet would be round






The finished product looking is very merge-y








It goes under the transmission or it gets the hose again


 
#19 ·
I know I am skipping around here but I could not build the rest of the exhaust because I had no idea what the shift linkage looked like (because it was not built yet) and because the exhaust was going to be routed under tail I needed to get to work




What bike is complete without rearsets anyway?

I love the rearsets Boxermetal puts out but they were not the look I wanted, much too clean and too nice. I like the look of rubber and steel pegs which say "when you drag me you will be in huge trouble" so I set about to build my own.

I unbolted the stock peg and stared at them I looked at where the Boxermetal rearsets normally mount and had an idea-rrrrrr, if I take the stock pegs and mount them where rearsets usually bolt up......

...so I got to work

Left peg first as it has the shifter. I cut the support and set it to the side








I then mocked it up to the upper hole in the rear peg support



Then I had to make a shouldered boss for the shifter to ride so I used a bolt (that was hard as Hades BTW) and put it in the lathe. I turned thread on both ends ad machined a section for the shift lever to ride










After I machined it I threaded into the peg on one side and nutted to the frame on the other and the shift lever pivots in the middle










On the passenger side I had to cut the squiggly piece out between the peg and the mount hole to get the correct height then weld it back together





 
#20 ·
Now I have to find a way to support them and since they are mounted near the old passnger pegs that seems like a good idea. So I cut up the old passenger pegs to join with the new rearsets.











I love molten metal








The finished product






bolted up and looking like I wanted








Got linkage (even if temporary)





Das Boot








The next chapter is the brake pedal and linkage
 
#21 ·
Yeah rear brakes since I built the rearsets I needed to move the rear brake controls so they are reachable. You can see how far away from the new location the stock lever is








So I removed the arm and cut off the portion of the lever that actuates the master just below the pivot bolt





Then I drilled and tapped what was left of the brake lever in order to bolt a "bellcrank" to that will be actuated by the pedal






I then found a "splined piece" (I dont dare say what it was) that captures the head of the pivot bolt and formed a bellcrank that would bolt to the stock lever that is drilled and tapped.







Ok do you remember the support I cut from the left footpeg behind the shift lever and the squiggly piece I cut from the right footpeg? Well in the interest of recycling and reusing, I saw the shape of what I wanted in these two "leftovers". So I did what any self respecting tinkerer would do and I welded them together and bored out the end that attached to the "splined piece", pressed in a 17mm hex and welded that into the arm.









I welded the Bellcrank to the "splined piece" and checked to make sure that when the two pieces were put together there was enough bite on the splines so that it wouldn't round out or break under heavy stomping.





I drilled a small hole in the head of the pivot bolt and tapped it with a bottom tap to retain the lever. Seems safe enough as there is no lateral moment with the bolt tightened.






The last part I needed a actual pedal piece, so I cut off the factory foot-trap; drilled it and tapped the lever so it would bolt on. And Viola, brake pedal with a stock brake light switch and actuating arm.









Next is exhaust , really , no joke
 
#22 ·
Now it is time to make the exhaust come out from under the trans and up the other side under the seat. So I have to make a ( kinda sorta) mirror image of the merge collector i just built.

I selected two 90s from the pile and spaced them apart just a little so i could expand them and slip a band clamp between them.









The flat plate my ground clamp is on, is tacked to both pipes to prevent movement i will cut it out when i am done building the merge





Here is that same piece of stainless pipe I am using as a form to keep the inlet round





Once i finished this half i welded both halves together to make this monstrosity








And here it is in place the shift linkage clears it although I might put a heat shield on the trans side and one on the leg side (something with lightening holes I think)



 
#23 ·
Since I am finally done I can start to route the pipes up under the seat to finish this portion off



















So here is where it exits











So there you have it, plenty of room for the tire and shocks and it should not singe my butt either.Pipes dont store heat the way an underseat muffler does.
 
#24 ·
Great build but even more impressive is the effort put into documenting this thing! Must be a hassle to take a pic after
every step. Repped!
 
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#25 ·
Thanks, I document it not just to be a post whore but to remind myself just what I did and how I did it.

That way, on my next project I won't do a cookie cutter replica, fresh new ideas and shit mang!

And, yes there already is a "next project" in the works, however it is classified right now :yamaha::Evil_smile:


There is a bunch more pictures I have not yet posted, I am just slow
 
#26 ·
Looking good so far! You can run baffles in your exhaust pipes, just gut a couple of the emgo universal mufflers off ebay. The baffles and packing from those are easily removed (one bolt holds them in), and then can be welded or bolted into your exhaust pipes.

Slightly baffled exhaust, super clean look.
 
#27 ·
Yeah I know about the internal baffles and dpending on how it runs I might make my own. The splines in the rear end are shot anyway so I am looking for an R65 rear end with a little steeper gearing.

At the moment I just want it to run and I'm close to that
 
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