A friend of mine has a 99 yamaha wr400f that has always ran fine until he took it out of the garage after the winter. When it is warmed up, it will die right away if you blip the throttle. It stalls out even if your taking the bike for a ride. I can't understand what would cause this do act this way being that it ran fine before hand. Thanks for any advice.
The accelerator pump on the FCR carb needs to be serviced (cleaned and lubed) regularly. When the fuel evaporates over the winter rust collects and plugs things up. It's probably time to pull the carb and clean things.