Author Topic: K100 build- making it up as I go  (Read 57695 times)

Offline jc55

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K100 build- making it up as I go
« on: July 04, 2016, 10:10:18 PM »
Hello, Guys. Thought I'd try and contribute since I've gathered so much valuable info here. I picked up a dealership serviced bike last week that had traveled around the country, but has been sitting for the last 5 to 6 years. This one has about 31,000 miles.

The fuel pump was locked up, fuel lines brittle, so I cleaned the fuel tank, ordered a new kit from Euro motoElectrics, and am replacing all of the fuel lines. I've stripped the outside of the fuel tank chemically, removed all fairings, entire ABS system, and alarm.

I've scoured the internet looking at every alternative to cutting out the downward slant of the frame tubes under the seat, and in my humble opinion, there is only one for the look I'm trying to achieve. I just hope that I can pull it off. I'm making the tank angle and rear upsweep of the frame, the same angle.

I'll weld the rear of the frame at this new angle after a single pie cut but BEFORE cutting off the rear hoop. Hopefully my pictures come up.

  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #1 on: July 05, 2016, 06:48:06 PM »
Today, I finished up the welds on the kick up portion of the frame.

I broke out the JD2 tubing bender that I haven't used since 2006, and had to get reacquainted with it. I made a 180 degree bend with my 1" die, then realized that the radius is much too small for the rear of the K100 frame. I dug deep and somehow managed to make one piece, first try, starting from 2 different ends with 4 bends total. I think it ended up being two 70 degree bends, and two 3 degree bends. I wanted to follow the rough shape of the rear of the tank.

I TIG welded the rear bar, checking and rechecking angles and position 4,782 times, it seems. I positioned the end of the bar so that it sits just a hair past the rear edge of the brake rotor.

The next challenge will be building the rear tail and seat pan, which should take a while. I don't have an English wheel but I have a few ideas.

Renthal ultra low bars and non ABS brake lines are in the mail. Thanks for looking!

  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline Martin

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Re: K100 build- making it up as I go
« Reply #2 on: July 06, 2016, 02:55:09 AM »
You can always tweak the angle by lifting the front of the tank.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline jc55

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Re: K100 build- making it up as I go
« Reply #3 on: July 08, 2016, 11:22:59 AM »
Thanks Martin, that's a good point.
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline Chaos

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Re: K100 build- making it up as I go
« Reply #4 on: July 08, 2016, 12:47:07 PM »
the tank never seems to look right once the fairing is removed.  Nice job bobbing the frame.
  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
sold 6/23
2023 Ural 2WD sidecar (BMW's bastard step child)

Offline jc55

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Re: K100 build- making it up as I go
« Reply #5 on: July 08, 2016, 12:49:09 PM »
I'm considering building front fairing pieces from either fiberglass or steel because I kind of agree.
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #6 on: July 09, 2016, 07:45:51 PM »
I've been trying to figure out specific mounting points and such and how everything will tie together. I made new shock mounting tabs and TIG welded them in. I decided to fab a bolt-in lower panel for the tail section. I made this panel out of 18 gauge for rigidity.

Next, I'm trying to lay out the tail and seat area. I don't have an English wheel so I experimented with a leather bag full of pea gravel. It seems somewhat doable so I may try a leather and sand. Worse case, I may go get an Eastwood or harbor freight English wheel, or find an old gas tank.
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #7 on: July 11, 2016, 09:29:22 PM »
Not much progress, but I did buy a $250 harbor freight English wheel. The same beat up panel in the previous post ended up looking like this after 20 minutes on the English wheel. Off to learn a new skill...
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline TrueAce

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Re: K100 build- making it up as I go
« Reply #8 on: July 11, 2016, 10:14:30 PM »
That's some impressive work there to most of us home garage types! Keep up the pics. What do you do for a real job?
  • Florida
  • '85 K100GS, '85 K100RSSC,', '94 K1100RS,'10 S1000rr,'14 Ural Sidecar, '15 R Nine T

Offline TrueAce

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Re: K100 build- making it up as I go
« Reply #9 on: July 11, 2016, 10:23:24 PM »
+10
  • Florida
  • '85 K100GS, '85 K100RSSC,', '94 K1100RS,'10 S1000rr,'14 Ural Sidecar, '15 R Nine T

Offline jc55

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Re: K100 build- making it up as I go
« Reply #10 on: July 12, 2016, 06:53:45 AM »
Thank you, TrueAce. Actually, anything I'm doing here can be easily done by anyone who uses Google. I'm just your average blue collar natural gas plant operator/electrician.

 It's always been a dream of mine to have a fully equipped hot rod shop so I've been buying tools all my life, and stumbled upon the opportunity to buy a really nice shop in a real economically depressed area. The Lord's been good to me and I'm blessed to be able to build everything from boats and model T's to my first motorcycle.

There's a lot of skill here and some really creative bikes that you all have.
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #11 on: July 18, 2016, 09:15:01 PM »
Well I finally had a day to work in the shop. Bike tails are so personal and 'artsy' that it's hard to know if you're nailing it or not. There is some awfully nice work out there.

I built a buck from plywood, hopefully getting the shape right. Like I said, it's just so tough because there's no real formula.

I hit that dog gone piece of metal for 6 straight hours today. I did the math...over 100,000 times! I used a piece of thick leather I had over a bag of store bought play sand. I then cleaned it up on the English Wheel, tapped some more, repeat as necessary.

I made a home made dolly for light shaping. There's a lot more work to be done, like welding in an entire rear strip. Duh, I should have used my shrinker.

Here's what I came up with so far...
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #12 on: July 19, 2016, 09:50:01 PM »
Today I had a couple of hours so I spot welded mild steel rod all the way around the tail from the inside. I welded up the back radius slits over a half round wooden buck so the the rear would be perfectly round. I'll use USC All metal or lead in this rod to create a natural looking radius all the way around.

  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #13 on: July 20, 2016, 07:20:14 PM »
Today I had a few minutes for some more design stage work. I sat on the bike and it felt just a bit cramped. I decided to take the angle of the tank and match the tail for aesthetics. I left 3/8" of a lip after the cut. I used a pair of glass cutting pliers (an absolute essential metal working tool in any shop) to gently work the edge as pictured.

Obviously, this changes the shape by widening it. I placed it in the shrinker and now we have a really nice professional looking lip. This beats a welded edge. Makes me wonder if I should've done that all the way around the bottom.

There's a couple of extra mock up pics for ideas.

Thanks for looking!
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #14 on: July 24, 2016, 09:06:16 PM »
Spent some more time on the English wheel and used a contour gauge to get the last of any irregularities worked out. I've seen some really non symmetrical work coming out of pro shops online, so hoping for the best.

 Before moving on, I had to figure out mounting. I want everything to be modular and easy to remove. I used some existing hardware for the rear mount and hemmed the edges of the strap for rigidity.

Now I can continue metal work from tail to tank and start thinking about getting a custom seat made.


  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline Vespa no more

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Re: K100 build- making it up as I go
« Reply #15 on: July 25, 2016, 11:02:03 PM »
Looking good. Well done

Nice to see the panel work done in metal not fibreglass - quite a different aesthetic.

Questions:
what tubing do you recommend for the frame? Impressive tube bender.
I assume you've annealed the aluminum (if it is) before the hammer work. Is there a particular gauge / thickness of sheet you are using?

I do like the derelict look seen on some cars - without the excessive hot-rodding: understated but quality.

there are a lot of cafe racers appearing but it's the ones that look a little aged are my preference.

But each to their own.

Keep the pics coming
  • Wollongong NSW AUSTRALIA
  • K100RT 1984, K1100RT 1993, Vespa VNB125 1963 :)

Offline jc55

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Re: K100 build- making it up as I go
« Reply #16 on: July 25, 2016, 11:23:34 PM »
Thank you Vespa, I appreciate the compliments.  The tail was made from 20 gauge mild steel, not aluminum. It is indeed amazing how much it can stretch without becoming brittle and thin. I made sure I did most of the metal work before welding so as not to harden the piece. I also used my TIG instead of my MIG due to the softer slower heat. I don't believe I work hardened it over the leather bag, although metal over metal most likely would have. Still learning shrinking and stretching.

My tubing choices were limited because I really couldn't get my hands on the exact size of the larger tubing. The wall thickness of the 1" tubing I had laying around was .095" I believe. It's not really load bearing and I did not remove the rear cross member. It was a decent slip fit.

Please give constructive comments on the following design...I'm still unsure myself...And I'm gonna start back up in the morning
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #17 on: July 26, 2016, 04:42:19 PM »
Since I didn't get any critiques, I decided to commit to my original design. I made the seat mounting surface the same angle as the valve cover on the engine, for aesthetics.  There was a lot of shrinking, stretching, edge rolling with my Niagara edge roller, seamer use, dolly and hammer and a little English wheeling on the side panels.

I bought this bike because I've always wanted to do a bunch of metal work on a bike.  I notice that a lot of bikes end their side panels abruptly before the tank, and I wanted to tackle that issue.

I made a front mount which clears the fuse box and cpu under the seat in case I want to keep those. I really want to build a bike that I can ride, so I haven't made up my mind on a lot of particulars.

Here are some pics. I butt welded and ground the left side panel into the tail. I'll blend the tail beaded edge to match the forward bead on the side panel. As it stands, yes, they are different.
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline jc55

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Re: K100 build- making it up as I go
« Reply #18 on: July 27, 2016, 04:59:21 PM »
Well, this was supposed to be a winter project but it's kind of clipping along. I added another support and started on the fiberglass seat pan. I've rebuilt a couple of boats lately so I had a roll of 1708 biax and some Fiberlay polyester resin. Everything starts with a poster board pattern, for me anyways. I used 4 layers of 1708. If you are a fiberglass amateur, You really shouldn't exceed 4 layers in one lay up. 2 would be better.  The cure puts out an immense amount of heat. I wanted a chemical bond on all layers so I did it all at once.

After it cooled down, I trimmed the shape on the band saw, placed back on the bike, used a file to follow the contour of the tail, then used the D/A sander for a final contour while in place. The whole thing takes about an hour or so.

I'll have to figure out how I want to attach the fiberglass seat pan so that it's removable.  I do have some ideas. Glassing in some stainless clips on the back maybe. Will have to trailer the whole bike and find a seat upholsterer who can put up with me, lol. 

Here are today's pics....
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline rbm

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Re: K100 build- making it up as I go
« Reply #19 on: July 27, 2016, 06:43:39 PM »
Excellent work on your build.  You got skills in many areas.  Just a heads up though to make sure you can remove the tank with the seat and tail in place.  That lip on the seat pan will prevent the tank from lifting unless you have a release mechanism for the pan or the tail.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline jc55

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Re: K100 build- making it up as I go
« Reply #20 on: July 28, 2016, 12:19:34 AM »
Thank you RBM, that means a lot. Especially coming from you. I can only hope that I can be in your good graces come "gauge time"  :2thumbup:

I'll design the seat so that it is removable on it's own. After that, both the tank and the tail will be removable independently.
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline Markus77

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Re: K100 build- making it up as I go
« Reply #21 on: July 29, 2016, 07:14:41 AM »
Looking forward to watching this project progress - I think it's going to be great - really impressive work with the tail piece!
  • Toronto
  • '94 K75RT

Offline sj2000

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Re: K100 build- making it up as I go
« Reply #22 on: July 29, 2016, 10:23:36 AM »
Nice work, I wish I had all the tools that you have.
  • Parker, USA
  • 1985 K100

Offline jc55

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Re: K100 build- making it up as I go
« Reply #23 on: July 29, 2016, 05:57:34 PM »
Thanks Guys. I was actually very unhappy with the tail. It's been keeping me up lately, lol. It's just a hair too long and it's too flat on the upper leading edge.

Today I pounded on it for another 3 hours on the leather bag, and ran it through the English wheel. I'm a lot happier. It's such high stakes to get this far then start beating on it again. Hopefully I'll quit posting tail pics and get on with it. I checked on some Amish upholsterer today, so we'll see about getting the seat done.

Ordered some clip ons also, so it's either those or the Renthal ultra lows.
  • Carrollton, Ohio
  • '90 K100LT '77 Gl1000

Offline TrueAce

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Re: K100 build- making it up as I go
« Reply #24 on: July 29, 2016, 06:18:42 PM »
You have the most professional build for a cafe K, equal to the K1 build by our amigo in Mexico City. The quick-release seat is very important I am still working on seat retention/release on my K scrambler. So many different ideas for K's, you have to do another, right?
 Thanks for taking time to share pics of your work.
  • Florida
  • '85 K100GS, '85 K100RSSC,', '94 K1100RS,'10 S1000rr,'14 Ural Sidecar, '15 R Nine T

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