People often ask me why I chose to work on old bikes. Why I make some of my own tools and not just go out and buy em. Why I reuse the old stuff, go through the hassle and not just help out the economy and replace it with something new. Well, they all have good points, but if you're not too serious about a ride and just want to have fun with it, reusing old parts add character and charm, as my pops puts it (inside, he really means it saves money). As for the economy, what about the environment! Every bike rebuilt is one less mangled steel pile on the trash dump.

If you're going to have to use your bike day in day out, every day to get to work then I suggest going for newer parts for reliability and peace of mind. If, however, you want to just mess around, learn a few things, and have some fun with a single speed, this is the writeup for you!

I started with an old and forgotten French road bike built by a company name Stella. They weren't to big of a company and when it comes to their bikes, I'd say Mediocre at best. This however, makes them cheap, a perfect match for this build.
Cheap usually comes with problems though, and this bike is no different. The rear wheel looks like something fell on it during its life in storage or it got hit by a car. Usually when there's a big damage like this, check the frame for bends and cracks to make sure its still suitable for use.
For this, you're going to need a donor wheel. Something that spins true and is the same size will be a good start. here's one.
I don't want to get into too many specifics, it'll spoil the careless fun but I must, i apologize. When you go for a wheel, try your best to find one that is from an American, Japanese, and or English bike as these are your best bet for a hub that's "normal" threaded. Watch out for Maillard hubed wheels as they use a proprietary hub design that can be a pain to find parts for. Another thing to watch out for is how "Dished" a wheel is. Multi speed (rear) wheels are dished (the spokes on the side with the gears are caved in more in order to give more room for the gears). This is bad if you're trying to put a single speed freewheel on there because it's going to put you out of line with your front chainring. So try to find a wheel that has as little DISH, or simply put, as simmetric on both sides as possible.

Here's the wheel I found, its dished as you can see, but not too bad.
As a side note: With what I've pointed out to look for, please please please, don't buy a cheap bike based on what kind of cheap wheels it has. For example, if I am or anyone for that matter is selling a complete bike, please don't call and ask how dished the rear wheel is or what kind of hubs it has. You do not buy a house based on what color the front doors are is what I'm saying. Wheels can be found separately and changed out later if you like, the frame condition, fit, and the whole performance of the bike should be considered. You'll never find a bike you want if you look at minute things like that.

My wheel came with a 5 speed freewheel, standard back in the day. The hub uses a clamp type tool to remove the freewhell.
I've made two tools that I usually use to remove these freewheels because they pretty common on old bikes. I think that a bike shop should sell something like this, I've honestly never checked and just made my own. First is just a 14mm socket with the face milled down so that two prongs are left, pretty simple. If you're going to make this though, use a deep drive socket, i'll show you why soon. The second tool i made is from an old adjustable wrench. I just filed down the nose to make two prongs that are adjustable.

The short socket i have requires that you remove the wheel axle before you can insert it, that's a huge hassle so I suggest making it out of the longest deep socket drive you can find.
Here I am using the wrench.. Turn counter clockwise to remove.
Once its off it looks like this. This is the threading I was talking about earlier. Again, Japanese, American, and Enlish bikes have the standard threading that persists to today. this is the same threading that is used on BMX bike wheels, which leads us to the next piece.

You're going to need to find or buy one of these. It is a single speed freewheel. These come on BMX bikes if you have an old one lying around. In case you dont, i have these for sale for only $6. you can buy em here or go to any bmx shop. To install the freewheel just twist it on, turn clockwise. the face with the 4 indents should be facing outward as that is what's used to remove it.
Now that you're done with the wheel, move on to the more fun part! Start by removing everything you deem unnecessary. Take off derailleurs, cables take off one brake and leave one on if you like (you need at least one brake dummy, how else will you stop, this isn't a fixie).

Derailleurs: Gone
After you're done with stripping down the bike to your liking, here comes the next hairy part: the crankset.
Here you have a couple of choices and things to keep in mind. If your bike is old, it might come with what's pictured above, this is called a cotter type crankset. There's a cotter pin that goes into the crank arm (red arrow) that keeds it rigidly pined to the bottom bracket spindle. To remove this, undo the nut on top, wiggle the crank arm and the pin should losen. After you pull the pin out, the crank should just slide out. Now cottered cranks are a bit tricky because its takes a bit more work to adjust them to get the chain line as straight as possible. At this point, if you have a few bucks, or your bike comes with it already, use a square taper type crankset as these have more adjustablity (you can change bottom bracket spindle lengths for one) in order to get your chain line straight.

I opted to use the stock crankset and modify it to fit my needs. I removed it and took it all apart.
I only left the big chainring on there so that it looks cleaner. and it probably saved me a couple of grams in rotational mass.
Now you're just going to have to play with it. At first all I did was mount the chainring on the inside of the crank spider in order to push the chain line inwards to match the rear freewheel (This usually does the trick). Here it is with its chain on, testing. You're most probably going to need a new chain because the freewheel as with all BMX stuff are 1/2 x 1/8th. this just means that the chain is wider than the regular 1/2 x 3/32 road bike size. You can get the chain here or any bike shop will have it.
Install the chain, get good tension in there, and turn it to see if it pops out. If the chainline isn't good enough the chain will pop out as you are riding. My setup failed the first test. In order to remedy that, I put shims between the crank spider and the chainring in order to further push the chainring in. after that, the chainline was almost straight and it rode smooth as butter. You're going to have to play with the litle mounting screws and bolts a bit too to get the right lengths for your setup but after you get this part down, you're done!
This tutorial was very brief but it really is that simple. Of course the tinkering with the wheels and the crankset will take a bit of time (most of it will jsut be looking for little screws and shims) but when you get it right, it'll work great. I didn't bother showing exactly what modifications I did to the crankset because it'll be a little different for everyone so you're just going to have to play with it.

There is one last suggestion that I have though. If you want a cleaner build, with no chainline problems and new wheels with shiny hubs check out my single speed wheels. These are not dished, they come ready to have tires and a freewheel installed. You wont have any driveline problems or any problems for that matter. They'll make a single speed build no longer than 3 hours! At my prices, they're a great addition to any single speed bike. Again, you can go here to purchase them.
Good luck and don't crash,