BR540 blower peters out after a few minutes running

My br540 blower was running fine yesterday. I refueled it with fresh gas today and after about 20 minutes it started to slow down and I had to feather the throttle to keep it running but it eventually quit. I checked and everything seemed fine so I tried again and after a few minutes it slowed down and eventually quit. Started again and when failing I pumped the bulb which caused it to immediately stop running. Changed the fuel filter, checked and cleaned spark plug and air filter, all OK. Restarted the blower and it ran for a few minutes at full power then
slowed/bogged down and quit. After some research here I will check the spark arrestor tomorrow but welcome any other advice.

Thanks, Howard

BR540 blower peters out after a few minutes running