The first step is to make the valve because that is the hardest part.
1. Cut a hole in the side of a straw but not too big.
2. Put some hot glue around the hole but not in it!
3.Stick a short piece of bendy straw over the hole. Put some glue
around the hole to seal it because the engine will not work if air
4. Straighten a paper clip to make the valve stem.
5. Cut a small circle out of a small piece of plastic for the valve plug. It should just fit in the straw. Make a hole in the middle for the stem.
6. Glue the circle to the end of the stem.
7. Cut a circle of soft material that is a little bigger than the plastic circle. The woven side of a face cleaning pad works well.
8. Glue this to the plastic circle.
9. Glue the paper clip in the end of a straw.
10. Make a hole in the other end of the straw. This will go on the crankshaft.
11. Now the valve is done! Try it by blowing in the end and sliding the plug up and down. It should not leak much when it is closed. If it leaks try step 7 again with a bigger circle of material.