CB100 First Build

R

rothko78

Active Member
Hi All

Been a long time lurker here trying to gather as much info and inspo as i could.

So on the weekend i decided to dive in and get an old CB100 to strip down and turn into a cafe racer of some sort.

Here are a few images of how she looks when i picked her up.







even found out where it came from


As this is the first bike i have worked on (previously worked on cars) the plan is to get it running and then put it together with all the parts i want like new tank, seat, bars, rear sets etc. Then once its all sorted and working well strip it down to the bare frame remove any tabs etc and powdercoat it.

I know this may seem the long way around but i figured this way i can make changes bit by bit and make sure they work and also to make sure i like the way it is set up before finishing the frame so i can make any cuts welds and the like before powder coating.......but correct me if i am attacking this the wrong way.

For the inspo i am planning on making it look like the Honda RC166 but with out the fairings. Chose this bike as when i was a kid my uncle used to play me tapes of the isle of man TT and the sound of that bike has stuck with me, so kind of making a visual tribute to it.

Hopefully i will be getting moving on it quickly and posting heaps of photos.

First thing i need to do is fix the kick start (broken spring) then new handlebars, controls and cables.

Cheers
Brad
 
Not the long way around, the correct way to build a bike.

Few other pitfalls to watch out for
-any bar lower then a "superbike" bar is really to low with stock pegs. There is a moped flat M bar that works ok. It's hard to fab rearsets for these bike to work with clubmans/clip ons.
-the Honda singles HATE to run with a pod.
-don't fall for the cheap replica mikuni carbs as an "upgrade"
-RYF remote res shocks are junk

Try and think is some real useable improvements that can be made.

How about a cb350 front end? Better forks and brakes.
M62 gazelle tires are nice and priced well.
Alloy rims can be had for not that much.
There is an old big bore trick that uses a stock cb750 piston, but on these motors the head is really the bottle neck.
 
she's beautiful...

rearsets aren't too bad on these singles, just make sure you first mount the rearsets where you want them and then think about how you make your exhaust... that's the main problem with small bikes as these 2 want to interfere... and don't make your seat too low because it's already a pretty small frame and you'll have to fold your legs double to get them on your rearset.

i'm building a cafe from a cb125t right now and all i can say: take your time and think everything over at least 100 times
 
and the front end swap is a great idea indeed. make it yourself easy and find a 125 disk brake with cable. btw, somewhere on here there's a list with all the front end sizes so you can see what you can fit on there.
 
I ran drag bars on my CB100 with stock pegs. Im 6' and it was fairly comfortable. A CB100 isn't a long distance bike anyways. I had no issue with my front drum stopping me at full speed, but better braking and handling is always good if you can make it work.
 
Thanks for the advice guys. Good to hear i am not going about it the long way.

I measured out the new tank dimensions and seat last night and had a sit on the bike to work out what would be comfortable.

surffly, good points, was thinking about what bike i could use as a donor for the front end swap. Will keep an eye out for a cb350 front end as well as a cb750 piston to bore it out. Any recommendations on a different head?

jungalist i think fitting the rear sets are going to be a challenge as the exhaust hanger looks like a good mounting point.

For bars i was thinking clubmans but may look at clip ons.

Found a replica dream 50 tank and seat last night so ordering those today. Also going to order new bars and controls from dime city today.
 
I dont know what your budget holds, but if you wanted to go bigger you could swap an XR200 jug and head onto that 100 crank case. However, you would need the XR200 crank and rod as well. During my project I picked up an XR200 full motor (turned over but didn't run) for $50. Might be worth looking into if you can find the stuff. Lots of stuff you can do to these little guys. May also want to look at converting to 12v over the 6v system while your in there.
 
I will start looking for an xr200 than.
Have set myself a budget for the build and as I got the bike cheap I can probably factor in more engine work.

Will definitely be going 12v with this build.
 
Howdie. Fun project, believe me. A couple of pics of my cb125 with XR200 motor.
 

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i have to follow this............i too, have a cb100 to build.
 
Looks like the 200 is a reasonably easy transplant.

Here is the tank and seat i am looking at, basically an unbranded sky team ace set up.



Does anyone know if i can replace the kickstart spring with out removing the engine?
The haynes manual only refers to it as part of another process with the engine out.
 
Have read bad things about the cable disc brake so staying away from it.
Found a good source of parts for old bikes here in oz so probably going to do the complete front end swap.
 
Greetings. The cable disc stuff is pretty weak. Lots of lever pressure and little braking. I adapted an MB5 disc to a CB200 hub and I am going to use a Chinese brake assy. WHEN or IF I find spokes I will make my caliper bracket. I want to use 1/4 in 5150 Alum. plate. Does anyone know if it is sturdy enough. Seem like it should be as the bike will weigh less than 200lb. Good luck on your build.
 
So bit of an update. Pulled off the clutch cover to find that the kick start spring is inside the case. Looks like the engine is coming out. Never pulled an engine completely apart before. So should be fun teaching myself.

Tank, seat, new controls and cables should arrive this week. Will then get it all fitted and everything in the right spots. Then time to strip it, pull the engine apart and paint the frame while it's all out.

Need to decide on a colour scheme. Thinking of using my abarth as inspo.
 
These motors run very well at 150cc and you can buy the kits from people like powroll or Sammy miller products.
As surffly has said the remote reservoir shocks are not much cop unless you have the know how to replenish them, Crazypj on here has made some work well. It's important that the rear shocks actually have damping and not just spring like so many of the cheap replacements. A front end swap is a good idea too. But be sure to either keep the mudguard or make a fork brace to keep them working as a single unit.
Rear sets are a challenge but can be achieved in a variety of ways if you look thru the Honda small build archives on here.
 
Thanks for the heads up on the 150cc kits. Was looking at a piston that would take it to 125cc with a rebore. But will email powroll, depends on the cost of shipping to Australia.

Looking at two ways of doing the rear sets. One is to use exhaust hangers from a cm185 that I saw someone on here use. Or make a bracket that mounts to the passenger footrests and possibly the swing arm bolt. Waiting until I get the seat and tank mounted this week to work out what would be best.
 
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