Modified the frame to have a horizontal cross bar as opposed to the sloped one in original.

From original post Assembly instructions:

Instructions

The handlebar must have supports and must have the supports fully removed and sanded. The large cylinder in the "all_pedal_parts" file connects the two cranks. The part in "all_pedal_parts" that holds the chain and has a hole going through it entirely will go on the large cylinder next to the right crank. The other part that holds the chain (with a hole going through half-way) will need to be glued to one of the axels, on the outside of the right side of the frame. Then one wheel will need to be glued to that axel, on the inside of the right side of the frame. The other axel will need to be shortened and glued to the other wheel to be put in the fork connected to the handlebar. The small rods in "all_pedal_parts" go through the foot pedals and into the small hole in cranks. You will need to sand some of the pedal parts.

Instead of sanding the axels, you could make the holes bigger for the front and back wheel axels in the handlebar and frame (in a modeling software or with a power drill like I did).

Make sure the back wheel is aligned as perfectly as possible with minimal rubbing on the frame when spun. This is the trickiest part. Attach a small rubber band to the pedal and back wheel to make sure the back wheel spins easily.

Then when you have the back wheel ready and the handlebar ready, you are ready to glue the two frame halves. When glueing, make sure the handlebar is in place and the back wheel axel is in place. Then the left crank and pedal can go on, glued if needed. When the rubber band is attached, you should have a fully operational miniature bicycle!

Original post: https://www.thingiverse.com/thing:309158