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Author Topic: CB100/125 Big Bore Old Skool Cafe Road Racer Build  (Read 2686 times)

Offline kittykatjaz

  • Posts: 29
CB100/125 Big Bore Old Skool Cafe Road Racer Build
« on: Apr 15, 2017, 21:58:33 »
Hi Everyone,

What better way to introduce myself than with my little cafe racer build. I have been into bikes since a kid and always loved the GP bikes of the late 60's and 70's. Even owned and raced a few.

After years of wanting to I am undertaking a custom build of what was a basket case CB100 frame with CB125 engine I picked up a few months back. The bike is an old bucket racer with an engine  modded with a 62mm piston, XL head, custom crank and cam. Unfortunately the big end is blown and the engine incomplete.

The goal is to build a custom bike that is compliant with NSW AU registration without needing engineering by leaving the frame and running structure as original as possible and doing all the ancillaries within the Australian Design Rules to the year the bike was built.

I plan on making as much of the gear as possible using aluminium. It is either 5052 sheet, 6061 plate, 7075 round. So far I have made the seat/tail piece, combined rear guard and electrical tray which is hidden under the tail piece, fuel tank, rear sets and various other bits. I am just starting on rebuilding the engine.

The wheels I will rebuild using alloy valanced rims with stainless spokes.

I don't expect a powerhouse of a machine, I have a first gen CBR900 for that. This is a fun toy for scooting around the local area :)

Jaz
 

Offline kittykatjaz

  • Posts: 29
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #1 on: Apr 15, 2017, 22:08:01 »
Here are some pics of the fuel tank construction. The fuel tank cap is a 2" Monza from the UK and tap is from an RGV250. It took a few extra welds to get pressure tight.

Offline kittykatjaz

  • Posts: 29
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #2 on: Apr 15, 2017, 22:13:57 »
The seat electrical tray and rear guard were made from the same material as the tank.

Offline kittykatjaz

  • Posts: 29
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #3 on: Apr 15, 2017, 22:27:04 »
Figuring out the rear sets was a tough one. I wanted to the mountings up high away from the centre stand mount instead of low like many of the others that have been done on the CB125. The pegs have to be folding for the use of a kick starter. The pegs and top supports are made from 7075 alloy which has a very high tensile strength. There is a lot of thinking required to make the first set of folding foot pegs that work well. I was surprised at level of geometry required.

I still have to make the gear lever and associated linkages and will wait until the engine is in the frame to do this.

Offline stroker crazy

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  • Posts: 3712
  • crazy as a fox
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #4 on: Apr 15, 2017, 22:57:26 »
Welcome aboard kittykatjaz!

Brilliant start to your build thread; tank and seat etc. look real good and the footpegs leave me speechless.

Can't wait to see what you do with the motor!

Crazy
“Ride like the Wind” W.H.

Offline canyoncarver

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  • Posts: 3062
  • 'hacking is learning'
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #5 on: Apr 15, 2017, 23:07:49 »
Really nice fab and welding work.  Looks like a fun build. 
--
YZF750/1000R The Fly
KZ 750 Twin
ZRX 1100
The Shovelhead springer chopper
A bunch of KZ's...some Suzukis', and a disassembled CB550
--

Offline kittykatjaz

  • Posts: 29
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #6 on: Jul 01, 2017, 08:09:07 »
The little tiddler is starting to take shape now. The engine is assembled, wheels done, controls connected and I am about half way through making the new alloy front guard. Everything that has been fabricated has been done in my little workshop and it has been an enjoyable experience. Once the front guard is finished I will start on the exhaust.

Offline kittykatjaz

  • Posts: 29
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #7 on: Jul 01, 2017, 08:25:12 »
The engine took a bit of work to get together. I had to buy a couple of parts engines to get all the missing bits of the gearbox, kick starter and all sorts of other parts. Then clean it all up and determine what to rebuild or replace. I replaced the big end and con rod. The crank halves were scored so I machined them and fitted thrust washers. The crank has been lightened somewhat when compared to an original. New 62mm piston kit sent from the UK which will make the engine close to 150cc. New timing chain and guides, new genuine seals, main bearings and lap the valves. Once all prepared then assembled. The head is ported though I have no idea what grind is on the cam. It could be standard but it looks like it has been welded and ground. Guess I will find out when it is started.

I fitted a new Mikuni VM28 flat slide carb. I also have a Dyna S ignition to go in.

Offline Luugo86

  • Posts: 642
  • '73 CB350, '78 XS650 Cafe Killer
    • ToadStool Cycle Co.
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #8 on: Jul 01, 2017, 08:26:20 »
Those are some TiG-Tastic welds. Well done man. May I ask what guage sheet steel you used to form the petrol tank and seat ?
Live to Die, Die to Live

Offline kittykatjaz

  • Posts: 29
Re: CB100/125 Big Bore Old Skool Cafe Road Racer Build
« Reply #9 on: Jul 01, 2017, 08:29:49 »
Those are some TiG-Tastic welds. Well done man. May I ask what guage sheet steel you used to form the petrol tank and seat ?
Thanks.

The alloy is 1.6mm thick 5052 grade.