the new guy. CB100 first custom

Roots265

Mmmmm Vending Machine Hotdogs.
hi all
just thought id say gday. (yep im Aussi)(wollongong in fact)
been riding bikes for a while now but am just about to start my first (hopfully first of many) custom build.

i got this little CB100 for free. its been sitting in my dads shed for around 20years.
it ran (with a stuck clutch) when put away but time has not been kind,
then engine is siezed, the tank is rusted out and a family of rats made home in the seat.
but im keen to nut and bolt it anyway.

plan is to oversize the 100 engine(125) do some lite headwork and custom upswept exhaust.
stretch a new tank a couple of inchs, fab a custom rear cowl out of my rusted tank.
clip ons or drop bars to get low riding position, rear sets to suit tank and bars.

iv got a Harley sportser for bruising the freeway so the plan for the cb is to make it fun round town.
it needs to stop and handle.
looking to upgrade the front to bigger forks and hydraulic disk with decent shocks all round.

here are some pics as she stands.
 

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Gday, looks like a good place to start mate. Just a little rusty and crusty.

Try spraying some WD-40 down the spark plug hole. The engine probably seized because one of the valves was slightly open. Just leave it over night and then gently try to turn the motor around. If it doesn't work spray a bit more and wait a little longer. You should be able to put it in top gear and gently bump it back and forward.

Have you considered swapping the engine out for a larger one? There are quite a few that should fit, even a couple of off the shelf Chinese motors.
 
Your CB100 is exactly like the one I bought a few years back while on a bicycle tour across the USA;I sold my bicycle in Nebraska and purchased the CB100 and rode'er back to the E. coast then later installed the CB125 engine & instruments along w/ front disc brake;it was a fun bike. I hope you enjoy your project. 8)
 
thanks guys.
i have dumped the oil/petrol from the case, filled the chamber and case with Diesel and sprayed the whole bike with wd40.
im heading away on holidays soon and will leave the stripdown till i return. 2 months or so.
it goes through all gears and spins in nuetral so im hopings its motly ok.

plan is to get it running with this engine/bigger slug while and see if it needs more balls.
if so ill build a 125/150 for it.(who am i kidding, ill probably do this anyway)

my biggest issue will be getting registered hear in NSW Australia as our laws are quite strict. especialy for what we call blue slips. (required for curently unrego'ed vehicles)
once registered you can get away with more.

to get it running i NEED a new tank.
dont spose anyone has a CB100 or 125 tank laying around they dont want.
ill pay good cash but everyone on ebay in Aus wants to make millions and postage from OS kills a bargan.
condition isnt a big deal as i will be cutting it up in the future anyway.
mines just got too many metal worm holes in it.

cheers
Roots265
i have the old papers, last regoed in 82. so i can prove its not an import.
 
Have you looked at the possibility of a 125cc tank fitting? I know parts for the CB125's are alot easier to get and cheaper here in Aus. Good luck with the build mate! Im building a little two stroke racer atm in Canberra.
 
Welcome from Georgia.........I'm in process of redoing a CB100 at this time.

Haven't been able to do much, recovering from surgery at the moment.

Good luck with the build, I will be following and hopefully help and get help along the way.

Once again, welcome.
 

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Just found your build. Subscribed. Recently got my 100 with a 76 125 back on the road. Fun to build, even more fun to ride there are quite a few 100 builds to pull info from.
 
Back from vacation yet?

Mine looked almost the same when I found it, but everything was full of water and completely seized.
 
yep, back from holidays.
unfortunatly on my return i hurt the engine in my car(77 Valiant) so wound up spending way too much time and money on that first.

started off the bike with a masive shed cleanout/ set up. this took another two weekends.

finally started the tear down on the bike this week.
i was planning on trying to get it running as is before the teardown but the entire wiring harness was shot to shite,

basically took the engine out, made a stand to stop it tipping over on the bench and started making a list of items to purchase. because im a nerd this list turned into a full excel spreadsheet for the build.



aside from all the consumables that will be needed to get it on the road again i also ordered a battery eliminator and reg/rect from Oregon Moto Parts, this will make it 12v and no batt.
need to work out what coil to get now.
im still trying to get my hands on a tank to cut up.
my bike has the fuel filler ofset to the RHS and i want to keep this feature but the only tank i can get is in the middle and quite expensive as well.
 

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It appears you got an unexpected bonus on your motor. Somewhere in the bikes life, the early one piece head has been replaced with a later two piece bigger valve head from a 124cc motor. You now have some cam options and can also modify it to have the cam run in needle bearings.
 
45exmayor said:
It appears you got an unexpected bonus on your motor. Somewhere in the bikes life, the early one piece head has been replaced with a later two piece bigger valve head from a 124cc motor. You now have some cam options and can also modify it to have the cam run in needle bearings.

Interesting, is the tappet cover offset to one side the indication of a 2 pc head? Otherwise it looks just like the 100........always looking to edumacate myself ;D
 
I looked too quickly and mistook the head bolts for the two piece head fasteners. (A victim of 70+ year old eyes and bad glasses). It is a stock 100 one piece head.
 
It's also hard to judge with the side pic..... interested to find out more about the 124cc head option though. I imagine it would create more power?
 
45exmayor said:
I looked too quickly and mistook the head bolts for the two. Piece head fasteners. (A victim of 70+ year old eyes and bad glasses). It is a stock 100 one piece head.


Or maybe a few too many......as in my case.....lol 8) ???
 
OK. some progress.
i got a tip from an add i put up in the buy and sell section of DTT. made some calls, took a day of work and drove allmost 7hrs round trip to Joes Moto near Canberra. result? i got the tank i needed.
while at the shop i had a look around and boy o boy was it worthwhile. i picked up a couple of spare wheels and brakes in great shape plus the holly grail, an SL125 motor to build up. best of all the bike it was in had a speedo reading 6.5k barely run in. best part was the prices were fare. they seem to want to keep old machines on the road. not just get rich.
so iv now got my style sorted. decided not to stretch the tank. cause i like how its sitting as is.
 

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Roots265 said:
OK. some progress.
i got a tip from an add i put up in the buy and sell section of DTT. made some calls, took a day of work and drove allmost 7hrs round trip to Joes Moto near Canberra. result? i got the tank i needed.
while at the shop i had a look around and boy o boy was it worthwhile. i picked up a couple of spare wheels and brakes in great shape plus the holly grail, an SL125 motor to build up. best of all the bike it was in had a speedo reading 6.5k barely run in. best part was the prices were fare. they seem to want to keep old machines on the road. not just get rich.
so iv now got my style sorted. decided not to stretch the tank. cause i like how its sitting as is.



wow.......looks cooool...............
 
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