My husband has just bought my 6 year old a Gas Gas txt boy 50 2002. When he purchased the bike the seller got it working and when we got it home my husband got it working fairly quickly, however after it had been turned off we couldn't get it kick started again. We ve had the bike to a mechanic and he's checked things like, the carb (fully stripped), the spark, fresh fuel and it still won't kick start.. please can someone help??