I know it's not an ATV but I need help from some engine savvy people.

2004 KTM 125sx- I was riding through an open field in third gear and all of a sudden the bike started to cut out and it slowed it self down and then died. Now when I try to kick it over it feels alot harder to kick and when it fires I can hear a metal clacking sound. Something obviously broke but what would be the first thing you would do? Pull the head? I think maybe I worked it to hard without letting it warm up in the lower gears.

 

I would pull the cylinder as it sounds like the bottom end of the rod. First pull the plug and turn it over by hand. pull the pipe and look at the exhaust side of the piston through the exhaust opening. If it all looks good then I would drain the radiator fluid, and pull the head to see the cylinder wall and top of the piston, if all is well there you will only have 4 to 6 more bolts to remove to pull the cylinder. That is where I think you will find your problem.