My $90 '71 cb100

Discussion in 'Some Assembly Required' started by redcb, Oct 29, 2011.

  1. redcb

    redcb Adventurer

    Joined:
    Oct 28, 2011
    Oddometer:
    31
    Hello all. This is my first post on ADV and im introducing my first motorcyle. I guess ill start the story from the beginning. I had wanted a motorcycle for a long time and i had scoured craigslist the entire summer nearly every waking moment even while i was at work. I barely had any money(still dont) being a college student. I found a bunch of really cheap projects and i tried to explain to people that i didnt have money at the moment but that i would soon and that i would pay them once i did. For some reason that didnt go very well, go figure. So finally one day i saw a cb100 for $120 and i immediately fell in love. I offered 90 and the next day it come home with me in the passenger side of my honda civic. Sorry no pictures of that but it fit perfect minus the handlebars. I brought it home and looked it over and didnt know where to begin. I have some background working on cars but never a motorcycle and i figured what better way to learn than to dive in. Hopefully im not in the deep end. Now onto the pics.
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    Ad picture
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    my first crappy cell phone pic, more to come
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    full pic
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    somewhat of final look. Hoping to make into some sort of cafe with very minimal budget
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    one big drawback(pronounced dent)
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    another pain
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    my biggest pain so far
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    got the taillight working
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    got the gauge and all other lights working aside from burnt bulbs
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    bought a sprocket cover

    Now after all this time and money buying parts, buying a charger, charging the battery, setting new points to spec, new condensor, new coil and new plug i still get no spark. If anyone has any solutions to my no spark issue i would really appreciate the help. And i plan on going on with this throughout the winter.
    #1
  2. sailah

    sailah Lampin' it

    Joined:
    Aug 12, 2005
    Oddometer:
    5,824
    Location:
    Turning expensive metal into scrap
    Congrats on your first bike, that should be pretty fun and fairly easy to work on.

    I rebuilt a Honda Trail 90 which was simiilar to your Honda motor. I can't remember why I wasn't getting spark either but I think it was the cam was not timed correctly after I put it back together. Stupid mistake but fixed it.

    I do know that I had a bad battery that I bought brand new. Mine was 6V as I assume yours was. I bought another new one, charged it and tested it and then got a spark against the block. My first "new" battery held charge for 20 seconds...

    Check you battery to see if you are getting decent voltage before you spend money on things like coils. EDIT: saw you have power to lights so maybe battery isn't an issue.

    I would also put a post up in Old School. That's where a lot of the motor wizards hang out and they'll get you running.

    Parts are super cheap for those, you know about DR ATV (Beatrice Cycle) right?

    Regarding the tank, you can try an pull it back out with a dent puller, or as my old woodworking boss used to say "Celebrate the mistake"

    Beat that dent in so it looks like it was supposed to be there, fill and fair it and then reshoot the tank. Voila, fixed on the cheap and the better job you do, the more people will comment on your cafe racerish tank vision:wink:

    If you haven't replaced things like wheel bearings, chain and sprockets, I'd spend some precious more dollars on those along with tires to make sure it's safe on the road. The brakes are easy to check just make sure they are in functional condition and adjusted.
    #2
  3. Rafiki

    Rafiki Some Dude

    Joined:
    Aug 4, 2008
    Oddometer:
    1,900
    Location:
    Petersburg, NJ
    check the wire going from the points to the coil and make sure its not grounded.
    Check the other wire on the coil and make sure it has 12v +.
    #3
  4. deaconjones

    deaconjones Been here awhile

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    Jun 5, 2004
    Oddometer:
    367
    Location:
    West TN
    That was my first bike!
    #4
  5. Bambi

    Bambi Been here awhile

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    May 14, 2009
    Oddometer:
    726
    Location:
    Linz upon Rhine, Germany
    Hello, boy with the red CB,
    you've got a very nice bike there!!! A guy at my school had one - back in 1974 - 1976 ... I always considered it the most prettiest bike in our school-yard. Restore it to it's former glory or make something pretty out of it. It's worth every try. Btw, I think, your indicators come from a Yamaha!. It should have the small, old, round usual Honda ones.
    Sorry, that I can't tell you something about your sparks. But remember, that your bike should be from the pre-electronic-ignition era. Lots of possible failures, but every one of them a simple affair. They often suffer from wear of the cam that open and close the ignition-points. Talk to old bikers in your town, at your school, at your work ... they should know!
    Kind regards, Bambi
    #5
  6. Bambi

    Bambi Been here awhile

    Joined:
    May 14, 2009
    Oddometer:
    726
    Location:
    Linz upon Rhine, Germany
    These points might hide behind the big round cover on the left side top-end of your engine. Just a suggestion ...
    More regards, Bambi
    #6
  7. Kubla

    Kubla Long timer

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    Aug 2, 2009
    Oddometer:
    1,407
    Location:
    Cincinnati, Ohio
    I also have a 71 CB 100 in my garage, I was advised to get the engine running before buying anything else for it, mine had been sitting for 30 years when I got it, mostly in garage's or sheds so it is in pretty good shape
    #7
  8. redcb

    redcb Adventurer

    Joined:
    Oct 28, 2011
    Oddometer:
    31
    Thank you very much for all your support and Sailah i checked out the site they seem to have some good stuff. Unfortunately for me the little money i had is now completely gone after i got myself fired from work. The project will continue but im going to have to really work with what i have until i find a new job and have expendable income. And no updates for now. Maybe over the weekend.
    #8
  9. Curtis in Texas

    Curtis in Texas Been here awhile

    Joined:
    Jan 15, 2006
    Oddometer:
    207
    Location:
    Rhome Texas
    If you are not getting spark at the points when they open, (use a wood pop sickle stick to check) but have voltage to them then check your case grounds at the points body.
    If there is no voltage to the points and no spark you might also look at the on / off switch on the handle bars.That circuit kills the power to the coil and condensor. It can be jumpered around to make it run. It gets it's power from the key switch.

    I still have 6 of the XL 125's in my shop. One of these days I'm going to restore them for the Grandkids.

    I've built and hot rodded more old 125 Hondas than I can remember.

    BTY, you can convert these to 12 volt now.
    #9
  10. redcb

    redcb Adventurer

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    Oct 28, 2011
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    #10
  11. MrPulldown

    MrPulldown Long timer

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    Truckee
    Sounds like the bike I bought in college. My advice is to buy as LITTLE as possible to the bike to get it in good riding shape..

    Congrates on getting it running. Now do not plan on major overhauls that will take a ton of money in small parts.. Just concentrate of getting more items working to the orignal state. DO NOT CAFE out the bike either. There is quite a bit of value in old working CB100s. Saw a decent shape one sell for $3k here in Reno, original.
    #11
  12. redcb

    redcb Adventurer

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    Oct 28, 2011
    Oddometer:
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    Thank you. I don't plan on spending a wad of cash on this bike. And I also don't see myself selling it. Its nowhere near being original and I doubt I would get even close to that amount. For now all the parts that I have bought are just crucial for getting a running, riding bike, aside from the chain cover but that could be a safety part I guess.
    #12
  13. k-moe

    k-moe Long timer

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    Jun 27, 2012
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    A little Bondo 'll fix that :rofl

    If it was mine I'd just leave it for now. Character is difficult to come by. You can always say the dent is from the face of the last person who asked to ride it :evil
    #13
  14. wfrpalm

    wfrpalm Been here awhile

    Joined:
    Apr 22, 2009
    Oddometer:
    133
    Location:
    between Akron and Y'town
    Thanks all. I got it running a few days ago but still have some work to do for it to be rideable. Got a short video of it running here.


    Hows come it wasn't getting spark?
    Get it road worthy and ride it , good luck and keep on posting.
    #14
  15. redcb

    redcb Adventurer

    Joined:
    Oct 28, 2011
    Oddometer:
    31
    K-moe I just might have to use that one. And wfrpalm I don't know exactly what the original problem was because I changed every component for the ignition system. What I do know is I had the points set up incorrectly(bigger gap) and the hardware was not in the correct order as far as insulators and washers and nuts and wiring. To get it correct I just looked at pictures online of new points systems and copied that. Also I bought an updated rectifier that seems to be helping a lot. The battery is holding its charge now for weeks instead of minutes.
    #15