Atomic Zombie's AfterBurner Chopper Bicycle




Another easy and affordable project! Transform a standard bike into something cool and unique in just a day or two - seriously! This is a great garage or backyard project that doesn't require special tools or skills, although basic welding is required.

This classic 1970's style chop was named and built by Enzo and Nathan (father and son team) from an old mountain bike that was found laying in the mud at the city dump.

Instead of the extended front forks, this chopper is roughly styled after the classic Raleigh Chopper bicycle with the straight frame and tiny front wheel. This project requires no extra tubing in the frame, and except for a few small add-ons, only requires cutting and welding two frame tubes.

Any mountain bike with 26 or 24 inch wheels can be used for this project. Besides replacing the seat and handlebars, you will only need a front wheel of any size smaller than the original rear wheel. A 16-inch wheel was chosen for this build.

Health Hazard
All welding processes produce fumes and gases to a greater or lesser extent. Galvanized steels produce added fumes from the vaporized zinc coating. Fumes from welding galvanized steel can contain zinc, iron and lead. Use precautions, including high-velocity circulating fans with filters, good ventilation, air respirators and fume-extraction systems.

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Step 1: Find a Donor Bike

The donor bicycle is a typical variety steel framed mountain bike. This frame is described as "uni-sex", but looks kind of "girlie" to me. Don't worry about it, dude, when we are done, that won't be the case.

The overall condition of this bike was fairly good considering it sat in a mud hole at the local dump, and was probably run over a few times by the bulldozer guy. This is a good thing, since we will be using everything but the front wheel, seat and handlebars.

Step 2: Take the Bike Apart

All of the parts are stripped and checked for damage (Photo 2) before the building process. Everything looked good so far, minus a rusty chain which will be used in unique a way. More on this later on.

Step 3: Raise the Bottom Bracket

To install a small 16-inch front wheel yet keep the frame looking somewhat like the original, something has to be altered or the pedals will drag on the ground.

Longer front forks would do the trick, but since that isn't the focus of this project, the only other option is to raise the bottom bracket.

To get the bottom bracket up higher, cut the frame cut in half at the seat tube where both the main tube and down tube used to be connected (Photo 3).

Cut the tubing as close as possible to the seat tube, then grind any remaining metal from the seat tube.

Step 4: Modify and Invert the Frame

Modification of the frame simply involves turning the front half upside down as shown in Photo 4.

Because the down tube (which is now the top tube) is shorter than the top tube (now the down tube), this places the head tube farther down, or the bottom bracket higher, depending on how you look at it. Basically, now the pedals have enough ground clearance.

This frame modification also adds more rake because the head tube angle is pushed forward. This will add a nice look to the final design.

Step 5: Weld and Rejoin the Frame

Here is the newly rejoined frame, with the front half turned upside down and re-welded (Photo 5). If you didn't look closely, you may not even notice how different the new frame is compared to the original.

However, the new head tube position and angle would make an almost impossible bike if the larger front wheel is to be used. Also, the top tube is larger in diameter than the down tube - another thing you normally don't see on "non-freak" bikes.

Yes, the front forks are already painted! Since there were three of us working on this chopper together, things progressed at an alarming rate.

Step 6: Using a Traditional Part in a Non-traditional Way

Originally, the plan was to weld the screen from an old satellite dish into the frame triangles in order to give the bike a cool "filled in look", but unfortunately, the satellite mesh was aluminum.

Welding thin aluminum to mild steel is not something that a simple AC welder can do, although I gave it a shot anyhow - oops. The mesh quickly turned into toxic vapor as the welding arc blew it away.

Enzo, being the creative genius that he is, came up with the idea of welding the original rusty chain into the frame instead, since it would have to be replaced anyhow due to mega-rust (Photo 6). In the end, it looks pretty cool, almost military-like.

Step 7: Find a Phat Seat

Finding a decent banana seat in a few hours around here was impossible, so Enzo came back with this humungous seat from what was probably an exercise rowing machine (Photo 7).

Although the freaky dude at the pawn shop charged him $20 for the thing the rest of the bike was free. This thing was just plain sick. This seat is at least twice as wide as a regular bicycle seat and three times as long.

Step 8: Make a Seat Support

To accommodate the new mega seat, a pair of chain stays were cut from one of the many bent and twisted frames in my scrap pile (Photo 8).

The idea was to weld the stays to the metal bit under the fat seat and then weld the other end to the rear dropouts on the chopper frame. Just about any old tubing would have worked, but these were handy at the time.

Step 9: Bolt Seat to Support

This baby's got back! The mega seat is bolted in place (Photo 10), and it almost dwarfs the rest of the bike. Because of the massive overhang on the seat, the rider only needs to sit near the back to pull some great wheelies.

Step 10: Prime, Paint and Put It All Together

The completed AfterBurner chopper (Photo 11). We added the 16-inch front wheel, some ape hangers, and a nice chrome rear fender - borrowed permanently from a granny-style bike (see Granny's Nightmare instructable.

Because of the frame inversion, the pedals are at a perfect height from the ground, even with this tiny front wheel. If the inversion was not done, the bike would probably be resting on the front chain ring.

Step 11: Sweet Ride!

Both derailleurs were tossed, and a simple direct drive from the large front chain ring to the middle rear cluster was chosen. This low gear ration allows for quick acceleration, and good wheelies, not much top speed though. Notice the frosted look at the fork tips and rear end. I had some dark red paint left over (Photo 12).

Step 12: Proud Co-builder Shows Off His New Ride!

Considering the short time it took to build AfterBurner, it turned out pretty good (Photo 13). Not too bad for a few welds and a $20 seat!

Step 13: A Successful One-day Build Ready for the Road

Nathan bombs down the laneway, putting AfterBurner through a barrage of test rides (Photo 14).

The bike rode much like a standard bicycle, mainly due to the fact that the head tube angle and over frame size were not much different than a normal bicycle. The ultra wide seat made the ride quite comfortable as well.

Not too bad, considering that the entire building process took one day!

Check out more custom bike plans, Builder's Gallery and Builder's Support Forum at '''Atomic Zombie Extreme Machines'''. Make sure to send us pictures of your completed home built bike projects. See you there!

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    28 Discussions


    8 years ago on Introduction

    CLunstrum333, No it isn't, but I have built 2 of them so far. And thanks for noticing.


    9 years ago on Step 13

    congratulations nathan! well done on building such a great bike!


    9 years ago on Introduction

    They have a bike like this at the Boise bike Project here in Boise.

    Just Curious: Is this the one in there?


    10 years ago on Introduction

    now i know why he needs such a big a little of my thoughts


    11 years ago on Introduction

    this is realy good and easy does any one now a way of modding some normal bars to make ape hangers? or a cheap web site

    2 replies
    I smell baconnobby_sk8

    Reply 10 years ago on Introduction

    I've done this once and it works allright. Take some regular 2-piece BMX bars and take out the middle piece. It may weaken them though it essentially makes ape hangers.


    Reply 10 years ago on Introduction

    I managed to buy some ape hangers for my girlfriends chop project at a bikers autojumble. I was after a new seat for a motorbike and spotted loads of ape hangers for between £5 and £10!!!! not bad. Autojumble is the way forward.

    I smell bacon

    11 years ago on Introduction

    Mountain bike!? the original bike had no suspension, how is that a mountain bike. Apart from that a pretty good instructable, I am hoping to do a similar thing with a BMX i found in a skip bin.

    1 reply
    lasersageI smell bacon

    Reply 10 years ago on Introduction

    You don't need suspension to class it as a mountain bike. The big knobbly tyres and gear range are enough

    Cam F

    12 years ago on Step 5

    The frame flips or turns in every pic!!! (~.~)


    12 years ago

    Translation: This could be very well called “How to ruin a bicycle that worked perfectly”. On the contrary. It was found at a landfill site about to be thrown into a pile of scrap metal and, no, it didn't work "perfectly".

    2 replies

    12 years ago on Step 5

    i like all this kinda stuff but i cant weld is there ny thing else i can do?


    12 years ago

    Do you take out the BBs when you work on it? I couldn't tell from th picture - but I didn't see the bearings in the disassembly picture... Just wondering if you have a method to remove it... I don't have a BB tool and I've destroyed one BB already with a vice and wrench :/ --- Still makes me wish I had/could afford a welder :P