I have an XS 850 too. up opens the THREE chokes... you can look to see if the choke lever is actually connected to all three and that they go up and down. My center choke was stuck in the up position.. ultimately I resolved it by permanently closing it and just using the other two. I´m having a terrible electrical problem... the electricity is being drained as it is running... I turn it off and the engine the battery is as dead as a doornail. Mechnaics are reluctant to look for a short. Very upsetting.