Usualy my 400ex is normal but it seems to have a wicked hesitation some times and sometimes pops , spits , and sputters . I put a new plug and always run 93 octane . I also put a new gas line on it . I havent gotten the carb off yet but I might soon. It all started after it sat for about a week and i went and started it and it wouldnt run right and was puffin out black smoke. Any help is appricated , Thanks

 

TrailBlazerguy250,

I would start with a good carb and air filter cleaning. One of my 150's was acting the same way. Hadn't ridden the bike in a long time and had some resin build up in the carb. You may even want to check your valves to see if they are within spec.

SB.

 

Yea I would have to agree with you since your jets might be starting to get clogged up from gas sitting in the bowl for too long and also how much gas do you have in the tank...clean the carb and make sure you can see light through the jets and clean the airfilter and make sure everything is up to specs like smb05 mentioned also the choke isn't on a little or anything and make sure the gas is on at the petcock because if you are on reserve and are running low it will act up.