Convert a small kid bike into a fun sporty looking silly riding adult bike.

Kids outgrow their bikes so fast but here is a way to put even the smallest 12" wheel kid bike back into action as a cool-goofy adult bike.

Re-uses/repurposes old items from the dumpster:
small kid bike,
crutch,
old steel tube,
wood mop handle.

Visit a good primer on Dumpster Dipping

Only had to buy the banana seat and a 5" long 1/4" bolt.

Step 1: Parts Needed

12" or 16" kid bike
Banana seat
Steel tube to fit in steering tube and support seat nose.
Steel tube that accepts kid bike stem
caster wheel from cart, furniture etc to form swiveling seat nose bracket
1" or 7/8" wood dowel (about 8" long) to connect caster threaded post to steel seat nose support tube.
Crutch to support back end of seat
3/8" bolt to bolt seat nose to caster bracket
1/4" by about 5" long bolt and 5-6 nuts to bolt seat back to crutch

Step 2: Pull Stem From Kid Bike and Make a New Tall Seat Support Tube Instead

Take stem from kid bike and measure tubing diameter needed to replace the stem and slip snugly into the fork's steering tube.

Slip it into steerer and determine length needed to get eat to right height for you.
Cut to length remembering to subtract height of caster frame that goes between tube and seat nose bracket.

Shave dowel down to fit snugly in top of stem tube. Pound it in at least 5 inches. Cut off protruding excess dowel. Drill snug whole to let you force thread the caster bolt into the dowel.

Attach stem tube to bike either slipping it directly in fork's steerer tube or using an intermediate tube in the steerer and slipping the stem over the intermediate tube. fit with aluminum can strip shims if needed for snugness.

Step 3: Miter and Weld Stem

Cut and miter (mitering means to cut or grind joint to fit together snuggly for welding) stem extension onto stem upright.

I used a tube with an inside diameter that the bike's stem fit inside (just like the fork's steerer tube).

Weld in place with goopy weld. I use a MIG (Metal Inert Gas) welder with flux core wire and no shielding gas. This really helps me avoid pretty welds.

Step 4: Gently Squash Crutch Arms

Cut armpit brace off of upper crutch arms.
Gently semi-squash aluminum crutch arms into ovals so the bike's rear wheel bolts can reach through after proper sized axle whole is drilled in each arm.

Step 5: Assemble the Seat Nose

With caster screwed tightly into wood dowel in stem, now you can assemble (bolt) the seat nose bracket to the caster bracket.

Step 6: Proto Type Testing

Take rear wheel axle nuts off and put drilled crutch arms on axle and re-tighten nuts (gently so as not to crack the aluminum).

For testing purposes the rear of the banana seat can be suspended by rope from the crutch while you finalize seat height desired.

Yes, it's already fun to ride.

Step 7: Cut Crutch and Assemble Seat Rear Mount

Cut crutch to length.
Drill hole for bolt (1/4" or largest bolt that seat eyelets accept.)

Assemble with nuts to keep parts in desired locations.

Step 8: Enjoy the Finished Product

Rides slow because of very low gearing on 12" bikes. (helps parents keep up with the little rascals)

The feeling alternates between:

Recaptured youth and your first bike ride or

It feels like the circus is in town or

you need to be wearing a Shriners' hat.

This bike was a proof of concept experiment for building a successor to my compact triangle bike