Honda Giorcub "big block"

Discussion in 'Battle Scooters' started by A_Vasiliev, May 12, 2019.

  1. A_Vasiliev

    A_Vasiliev Red, white and blue.

    Joined:
    Dec 7, 2007
    Oddometer:
    1,552
    Location:
    Voronezh, Russia
    Hey wow, long time no talk, eh! I used to shitpost on this forum back when I was a dumb late teen / early 20's stringbean, and now here I am, back a decade later and actually in possession of some motor vehicles for the first time in what feels like forever.

    This thread is going to be a bit of a long one but half the story is already done - I'll have to tell it in a flashback before we start actually moving forward.

    Let's start at the beginning, I suppose. The Honda Giorcub. Ever since I found out about the existence of this fairly unknown crossbreed between the Giorno and the SuperCub, I've been hounded day and night by the idea of making a "sleeper" scooter using it as a rolling chassis. Something that will have a little more oomph to handle city traffic, be a little more fun to rip around on day-to-day, but not look much different from stock. Anyone who's messed around with pitbikes knows they're all based on the Honda Cub engine design, so putting 2 and 2 together should let you know where I'm going with this already.

    The idea was banging around in my head for years, but I was always busy with work, or living in an apartment where I had actually nowhere to put the scoot, no garage, etc. Then at one point we bought an apartment where suddenly, there was room to store stuff like this nearby. And the cogs started spinning.

    At one point I was on a business trip in St. Petersburg, and happened to idly visit the local motorcycle buy/sell auctions and lo and behold, there was this little red Giorcub. The location was a 15 minute walk from my hotel - it was like the voice of a benevolent God saying "go look at it now". So I did. The owner was a gangly 20-something who looked like a hipster - no big shock there. I looked over the bike. Rode it around the courtyard of the apartment building. And said "I'll take it".

    The next day a friend of mine swung by and we loaded the thing into his work van and drove it over to his apartment. Cargo elevator, 16th floor, rolled the scoot into the bedroom he and his GF rented in a 2 bedroom shared apartment at the time. His girlfriend has the patience of a saint and I will be forever grateful to her for that.
    [​IMG]

    The next day I figured out where the nearest freight depot was and rode the scoot over there, sans gear. Drained the tank, boxed it up, and sent it to one of my friends so he could receive it, as I still had another week or so of business trip to go.

    [​IMG]

    Some of the pics show the rough spots in the Giorcub's bodywork. We'll go over these a bit later.

    [​IMG]

    That's all for now. Thanks for reading my rambling and I hope you tune in, there's already a good bit of material to write up and post, so I'll try to keep updating this regularly.
    #1
    cheapeto, OldCoot and BikePilot like this.
  2. OldCoot

    OldCoot Been here awhile Supporter

    Joined:
    Oct 2, 2007
    Oddometer:
    585
    Location:
    Blue Ridge Mountains
    :lurk
    #2
    rv-rick likes this.
  3. A_Vasiliev

    A_Vasiliev Red, white and blue.

    Joined:
    Dec 7, 2007
    Oddometer:
    1,552
    Location:
    Voronezh, Russia
    It's been a while since I've updated this thread, but I've sadly been a bit busy with life and working on my CRM (and riding it) to work on the Giorcub. However, there have been some major updates recently, and I'll go through them in chronological order for you now.

    Back in the early days of spring, I had ordered an exhaust meant for a Honda Grom for the project. I figured hey, it was a close enough fit, 125cc is the same size engine I was putting into the scoot. I was mostly right, but it did end up requiring some cutting and fitting to make sure the pipe didn't hit the engine or chassis anywhere, to ensure clearance for the muffler, and to make sure the kickstarter would still clear the exhaust (it's an electric-start engine, but I'd rather not have to rely on push-starting it if the battery happens to die).

    P_20180922_173828.jpg

    The pipe ended up getting cut in 3 or 4 places, trimmed and rewelded. Thankfully I have a TIG welder in my neighborhood who charges a pittance for this sort of thing.

    IMG_20190727_192310.jpg

    The engine required some slight modification as well - the rear engine mount was a drop-in fit, but the top mount needed to be reamed out a few millimeters to work with the stock engine cradle bolt. A 10mm drill bit did the job just fine and everything else bolted right up.

    IMG_20190420_164836.jpg

    The intake is a Mikuni VM22, mated to a step-up adapter I made out of a tapered Samco silicone intake manifold fitting, angled 45 degrees to allow the K&N filter to fit into the stock airbox location.

    IMG_20190423_013925.jpg

    The only thing that needed to be modified was the center tunnel of the scoot needed to be slotted to allow the carb and throttle cable to pass through it - there was simply no room under the tunnel with the much bigger carb, intake manifold and engine to avoid doing that. I made a custom throttle cable and it was routed up into the seat and then back down and around the engine up towards the twist throttle. This avoids sharp bends and keeps the throttle action smooth and kink-free.

    I also ended up sandblasting the stock wheels and hubs, and powdercoating them a very light gray. The worn out old tires were replaced with 3.50" wide Pirelli SC-30's for that retro look. I did the messy white lettering myself (I almost managed to color inside the lines, even). The rear sprocket was replaced with a new 33t Takegawa unit.

    K0OHdYVOCQc.jpg

    The front shocks were replaced with bright red units meant for the rear of a Yamaha Jog, and the rear shocks were replaced with chromed units from some other moped. The rear shocks ended up being trash - I will replace them when I install a Honda Monkey extended swingarm (which a Japanese tuner on Instagram insists should fit without issue as long as I don't extend the swingarm more than 4cm).

    9EGIViFkI_A.jpg

    I also spent a while figuring out the electrical wiring, as I was trying to mate half the wiring from the stock Honda harness and the wiring harness from the 125cc engine I chose to use. It took some poking and prodding and experimentation, but I eventually got it figured out.

    jQt5gyc6XQ4.jpg 9l_s1WBxL6Y.jpg

    That's all for now. As of right now, I need to get a few things figured out still (for example, why my headlight and taillight don't work, but my blinkers and brake light do). I have pretty much maxed out the amount of teeth on the front sprocket I can get (17t) and it cruises comfortably at 65-70 km/h, but I'd still like to go a little higher on the gearing simply to keep the RPMs down in top gear. 1st gear is a little bit useless because in 2nd, the engine still has enough grunt to pull me from a dead stop pretty quickly. I think the only thing I can really do now is go down to a 30 or 28 tooth rear sprocket, but I really don't want to replace the expensive Takegawa sprocket I just bought for no reason.

    The exhaust and intake are predictably loud, a bit too loud for me to be comfortable cruising around my neighborhood, so I'm thinking about how to make the dB killer insert that came with the can a little more efficient.
    I'll leave you with a few full size pictures of the build as she stands right now. It still needs some body work, mostly to get rid of the scratches and worn paint on the hard plastic parts, and getting the electrical stuff figured out, but she's basically done for now.
    IMG_20190727_192646.jpg
    IMG_20190728_195438.jpg
    #3
  4. cheapeto

    cheapeto Been here awhile

    Joined:
    May 13, 2014
    Oddometer:
    174
    Location:
    York PA
    I love the way you made it yours. Nice work man!
    #4
  5. DaBinChe

    DaBinChe Long timer

    Joined:
    Dec 28, 2007
    Oddometer:
    2,826
    Location:
    Santa Cruz Mtns.
    Didn't even know something like this existed. Long time ago I wanted to do something like this, put a CRF motor into a Metro.
    #5
  6. DandyDoug

    DandyDoug Long timer Supporter

    Joined:
    Nov 30, 2007
    Oddometer:
    1,719
    Location:
    Lewisville, Nc.
    I love this build.
    Kudo's to ya man , in my garage nothing stays stock very long , but you be da king !!!
    #6
  7. A_Vasiliev

    A_Vasiliev Red, white and blue.

    Joined:
    Dec 7, 2007
    Oddometer:
    1,552
    Location:
    Voronezh, Russia
    Took the scoot out for a quick spin yesterday. Will probably do the same in the next few hours. Slowly but surely breaking in the engine, I'm at around 50 or so kilometers on the engine so far, so ~2 hours or so of total run time. The exhaust is a bit too loud even after all the tweaking I've done with the core, so I've ordered a two-stage dB killer that I hope will do a better job of taming the roar.

    IMG_20190829_154604.jpg
    #7
    cheapeto, The Virginian and DandyDoug like this.