Step Thru City Bike

Moto

Member
Jan 7, 2012
403
14
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
3,988
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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
3,662
150
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
31
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

Active Member
Nov 11, 2016
229
181
43
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

Active Member
Nov 26, 2017
153
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72
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

Active Member
Nov 26, 2017
153
35
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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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