Step Thru City Bike

GoldenMotor.com

Moto

Member
Jan 7, 2012
403
15
18
San Francisco, CA.
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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wheelbender6

Well-Known Member
Sep 4, 2008
4,059
221
63
TX
Tensile steele frames are plenty durable and absorb vibration better. The older the better. Year 2010 and newer steel frames are less durable.
 
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cannonball2

Well-Known Member
Oct 28, 2010
3,682
220
63
Colonial Coast USA.
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!
 
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junglepig

Member
Oct 28, 2018
78
32
18
Georgia
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!
 

dogcatcher

Well-Known Member
Nov 11, 2016
272
283
63
Texas
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!
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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Larry Trotter

Well-Known Member
Nov 26, 2017
476
306
63
76
Very nicely done! I just finished up doing a little mod to a Big-5 700C fixie and put suspension forks from a Roadmaster on it. It seriously made it into a totally different bike to ride. I bought the entire Roadmaster at a good will store for $9.00 and salvaged the front wheel and forks. Put a 1.95 tire on the 26 inch wheel and life was really good. You should give it a try, the ride is amazingly improved. Pictures in a few minutes. Larry
 

Larry Trotter

Well-Known Member
Nov 26, 2017
476
306
63
76
Before the fork mods The stem was about an inch longer so I just used the lock nut from the old forks to lock the new ones and then topped it off with the nut.
 

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