I have a Stihl BR550 blower that has many years of use on it. It starts up fine and runs ok for a few minutes, but then it bogs down and wont run any higher than idle with throttle fully engaged. If i keep the blower on and push the primer button, the blower comes back to life a bit but then goes back to bogging down. Sounds like its not getting enough fuel? Has anyone else had this problem?