Step Thru City Bike

Discussion in 'Motorized Mountain Bikes and Road Bikes' started by Moto, Sep 25, 2018.

  1. Moto

    Moto Member

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    This is my latest build. I have had this 50cc engine for about 4 years now, dont have any idea how many miles are on it, but it is a lot.

    I found this frame for free and it was exactly what I was looking for. I have been wanting to build a really compact CG bike for a long time. I love how the engine fits perfectly.

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    I was dubious about the strength of this Free Spirit frame, so I welded a 1/4" plate behind the chainstays to beef it up a little bit. While I was at it I cut up the stock tensioner and welded it to the chainstay as well. The rear sprocket is stainless steel and mounts to a disc hub. The rear motor mount is also welded and does not use the typical aluminum block between the case and frame, this was necessary to make the motor fit.

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    The bike uses an offset intake and runtong dellorto clone carburetor. This setup gives nice low end power paired with a stock pipe and 41 tooth sprocket. The top end is not too bad either. The carb has a #65 jet.

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    I got an ATV thumb throttle that also has a brake lever which pulls two cables. This does a great job of simplifying the controls. I thought I would miss the twist throttle but I really like the thumb throttle. And the brake lever has a ton of leverage which helps the crappy brakes stop better.

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    I also welded the rear rack, notice the built in U lock mount. I use this bike to get groceries so its nice to have something big. A friend can also sit on the back :) I love the 'stock-like' look of this bike. I was trying to make a motorized bike that felt more like a legit moped and this has been doing it for me....
     

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    #1 Moto, Sep 25, 2018
    Last edited: Sep 25, 2018
    junglepig and Dan like this.
  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    I like it! Kool bike.
     
  3. Dan

    Dan Staff
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    Niuce!
     
  4. wheelbender6

    wheelbender6 Active Member

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    Tensile steele frames are plenty durable and absorb vibration better. The older the better. Year 2010 and newer steel frames are less durable.
     
  5. cannonball2

    cannonball2 Well-Known Member

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    Great build! I have built three step thrus but on the more common women's frames with the lower bars. I also welded the motor mounts.
    You have a nice compact well thought out bike there!
     
  6. Moto

    Moto Member

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    Thanks for the comments guys !!! @cannonball2 I was definitely inspired by some of your builds.

    yesterday I made a new front rack:

    IMG_9669.JPG IMG_9671.JPG
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  7. floridaboy

    floridaboy Member

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    I like your rack ideas it gave me some ideas for a rack for my bike. A nice clean build.
     
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  8. junglepig

    junglepig Member

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    I like that a lot.
    In searching through Craigslist and FB for bikes, it seems like some of the nicest and least expensive cruisers are old step-thru ladies' bikes.

    Looks like with some welding capability these lend themselves to a CG well.
    Nice job!
     
  9. dogcatcher

    dogcatcher Active Member

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    Moving the cross bar up just a little will give room for the CG engines, and make it easier for us old crippled up guys get on and off.
     

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