My recumbent exercise bike, just under two weeks old, started making a "thunking" noise about a day and a half ago. What happens is every single time I do a full rotation with the pedals, I hear a thunk noise in the front end or something. I'm not sure where it comes from up there since I can't pedal and get down and listen.

There is no thunk noise when I pedal with my hands and listen, nor is there one when I move my feet to the outside edges of the pedals.

Considering it's so new, I'm really wondering what this is. I adjusted the seat once and the noise went away, but it came back after about a minute.

Sometimes it's just a subtle little noise, other times it goes THUNK quite loud, as if a marble hit the side of the bike or something.

Anyone know what might be up?