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Here is my latest project:    For the frame, I chose the XL100.   It has the wheelbase of 48", which is the size similar to a Dream CB50r.   Also, it has rear seat tubes that I can weld on a pair of rearset brackets.   The CB100 tubes are a bit further inboard and higher.  This frame has a larger seat frame, including a rear hoop, to attach a full cafe seat.  The swingarm is 2" longer for better handling.   I can bolt a cb125 motor into it.    Finally, it has the bottom frame tubes where the CB100 frame is open.

frame 1

Here is the frame as I received it. 

 

frame 2

I started to grind off extra tabs.   It will need more grinding to finish it off.

steering stem 1

I went with a steering stem off an XR185 for a few reasons.   One, it has an aluminum double pinch lower clamp, versus the steel single pinch bolt normal version, for a stiffer front.  It has a lower offset (.75" vs 2.25") to allow a steeper rake.   Initially at 29 degrees, the trail is longer but I will decrease it by raking the front lower.  It will be similar to most modern sportbikes.   The stem is removable.    Good thing since the original stem was 1" too short.  I grinded one off a stock XL100 and just clamped it in.  The bearings were upgraded to tapered roller bearings for better steering feel.

steering stem 2

Here is the stem after I blasted them.   I'll follow up with some polishing and buffing.

forks 1

For forks, I chose conventional versions from a later CL175.  It will accept 15mm axles and the sliders are 31mm, a bit larger than the stock 27mm.  They are also a little shorter than the stock ones by 2".   This will help lower the front end.

front wheel 1

The front wheel will be off a CL175 as well.   It is sized at 18" (1 inch smaller) and the drum is larger, 160mm versus 120mm.

front brake plate

Front brake plate.  It is dual operated brake shoes as evidenced by the linkage, versus single lever shoe of the stock brake.  I was going to use the 180mm drum off the CB160 but felt it would look to large.

drilling drum

Here, I cleaned off the paint and started to drill some vents.   I used a 1.25" hole saw and the drill press set at the lowest speed. 

rear drum 1

The rear drum is standard 120mm CB100.  I wanted something small for weight savings.   I don't need a big back brake.   Here it is blasted prior to polishing.

alloy rims

For rims, I got a good deal on some 18x1.40 (WM0) alloy, non-shouldered rims.     They are anodized rather than polished.  I don't want too much shiny parts on this bike.   I want it more satin.   I'll mount up some stock size tires (2.50 and 2.75) in some more modern tires (IRC NR53 or Bridgestone BT39ss race).   Same size as the CB50r.

forks mounted 1

I mounted the forks to check fit for the steering stem.

rearsets 1

Here are the new rearsets from Durgam of the DTT forum.  I cut down the brackets to weld on the frame.  These are actually exhaust brackets off a CM185.

I'll use a stock CBR900rr shift arm and rod.     On the brake side, I'll use a stock cable off a MR250.   I prefer the look and feel of cable over a rod setup.

motor 1

I scored a complete CB100 motor but the piston was trashed.  Surprisingly, the bottom end is OK with no rust!  I will change the cases to CB125 parts so I can fit a complete 125 top end (cylinder, high compression piston and head).  The CB100 cases will require the opening to be bored out.    Hopefully, these gears will swap directly into the 125 cases.   Also, the gears are close ratio.

plated spokes

12-10-11:  Today I started to cad plate the spokes and some misc hardware.   Comes out a little dull and needs some buffing with steel wool.

 

plating setup

Here's my setup.   The left tub is a mineral spirits bath prior to plating.  The power supply in the background is set just under 1.4 volts by adjusting the current.

 

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