5th grade. Bought a fly by string airplane from a elderly retired neighbor for $2.
He said he tried to start it but never got it running. I tried all afternoon to get it to fire.
Finally figured out I could drip fuel into the carb and it would "hit".
I found that the cool looking blue fuel line was clean and the cool blue was gelled fuel.
Rolled a socket over the line and squeezed out the bad fuel. Thing started right up.
I ran to the basketball court across the street and took off. Made about two laps and flew it into the ground, hard.
There were sooo many pieces. All broken, last time I tried flying.