He was joined by dad Stuart, 35, who completed a second loop around the loch.
Stuart, of Markinch, said: “He was watching Children in Need when it was on and we were trying to explain to him that there are kids worse off than he is, and he’s quite lucky.
“We were saying how everyone was doing different challenges so something must have clicked and he said he wanted to do a challenge.
“He’s always loved to cycle.”
Alfie’s total of £240 from his JustGiving page was boosted by nearly £200 in pledges on his sponsorship forms.