What setting on fujifilm fs100 to shoot clear photographs?

I have been taking photographs for some time now. My main area is landscape photography, my photographs are quite clear in landscapes but when I try to take pictures of my boyfriend in his go-kart on a track racing I cannot get any that have enough detail to print in an enlarged size. I desperately need help in making my images clearer. The photos look good from a bit away but when I zoom in or crop close you realise that the quality isnt that good. Please help!