HELP 400 problems

[mxrdr]

hey just need some quik help my400ex hasnt been ran almost all winter cuz i was always putting new parts on the frame , stearing steam bars ect. and now i start it ill revv it up and i t will rev back down ill pin the trottle and it will accelerate for a second than die out and makes a low woa woa sound {ha if you know what that sounds like} and it was backfiring after this happend. i do no know whats wrong with it i have not even looked at it to see what was wrong please help though when i get home im gonna look
thanks
pat:macho

[standardryder]

sounds like jetting problems. usually if it backfires it means it to lean, but they usually run a little bit leaner in the winter. try taking out your spark plug, if it is white then it is to lean.

[cals400ex]

make sure the bike is fully warm before getting on it and also make sure you have plenty of fresh gas in the tank.