My sons stock 50 will run all day long when dry but as soon as he hits a descent puddle at speed or small creek crossing the bike will sputter and or die off at idle. You can get it started again and keep it at high idle with the throttle for a few minutes then it runs fine again. Seems like something is getting wet then evaporating then it runs. What is it?. I checked if the spark plug cap was cracked or broken but it looks as good as new. This bike has about 20hrs on it. Thanks for any help.