hi gus little problem with my yz125, about a month ago i was riding and the bike bogged out like there was no spark but there was any way took it home cleaned carby, new box oil, spark plug she started up ran fine for an hour then bogged out again any way bike shop told me piston and ring so $250 later new piston ring started ran like a dream after run in but after an hour same thing would not start again while out at the trak. got home first kick she fired up??? WTF is wrong with my bike??? thanks peeps