I just put a new piston and rings in my 06 yz450f. On the first test ride I went to a new riding area in the woods. this place was very tight and dangerous; never shifted out of 1st or second. The bike ran fine but got a little hot of course. I crashed while crossing a big log in the trail. the bike would not start for about 10 minutes. I had to turn the gas off and hold it wide open to get it to fire. Once going again the bike ran fine as long as i didn't hit any whoops. Every time i hit a bump bigger than a foot high the bike would bog out and then return to normal operation once over the bump. I did notice my gas tank seemed to be bulging out my radiotor shrouds on each side of the bike. Gas was also coming out of the gas tank cap before the vent house. I rode to the truck and went home. I fired the bike up the next day and it started second kick. Any idea what the problem was here?