The challenge to meet the 200 mile mark came when Keiran bought his new bicycle at John's Serious Cycling in Magnolia Park.
"If you go to a bike store you can usually get a discount of some kind," said Keiran's grandfather, David Paster, an avid cyclist. "We went to buy him a bike and I said, 'I usually get 15% off.'"
Instead, the store owner gave Keiran a free odometer, challenging him to ride 200 miles in two months. If Keiran could do it, the store would offer him a $25 gift certificate.
"It started with that, someone giving him a goal," Keiran's mother, Tisha Paster, said. "It developed into a passion."
Paster began home-schooling her son this year in order to better tailor his education to his interests in computers.
And cycling, she said, quickly became a source of instruction.
"It became a very hands-on learning experience," she said. "I was really able to see how learning can happen in everyday life."
As part of a math lesson, Keiran figured out how many miles he would have to cycle each day in order to meet his goal.
"Five miles a day, five days a week," he rattled off. "Twenty-five a week means 100 each month."
He also researched the history of the bicycle and studied the rust-free aluminum that makes up the frame of his bicycle in his science lessons.
The determination to ride the 200 miles came entirely from her son, Paster said.
"He's too young to bike by himself -- he has to have an adult with him," she said. "There were lots of moments when I was like, 'just leave your bike at home.'"
Keiran, however, refused to leave it a home. While his mother walked to pick up his younger sister from kindergarten, he rode along. Some days, he would bike with his father to the bank.
"I'd wait outside and guard the bank while he went in," Keiran said.
The young cyclist also took the opportunity to spend time with his grandfather. Last weekend, Keiran and his grandfather covered 24 miles in a single ride, traveling from Culver City to Hermosa Beach and back again. The trip put Keiran a handful of miles from his goal, which he reached on Monday.
"I don't know what I'm going to do with [the gift certificate]," Keiran said.
He does know, however, that his passion for cycling has only just begun.