Stihl br420

[Gregs mowing]

Hi.
Got a 2019 Stihl br420. Starts fine but bogs down and doesn't run right. Often cuts out. Can run smoothly on half throttle lock on the choke lever.
Tried new carb. Same issue.
Wondering if it's plug or some filter or air leek?
Any help much appreciated as always.

[Mick]

Could be any of those things to be honest.  or it could be Crank seal or crankcase air leak, fuel hose turned to putty, fuel filter, blocked exhaust or port etc.