Engine INTAKE AIR LEAK ?

My two year old Troy Bilt four stroke string trimmer was hard to start and then wouldn't run any faster than idle. Thinking I had a cure, I installed a new Troy Bilt OEM carburetor fuel filter, and gas lines. Now it's still a little hard to start and will run full speed only with the choke half closed. Reading other forums this seems to be a common problem.

My Troy Bilt, eight hp "HORSE" tiller is more than thirty years old and running it's second motor so I thought I was doing right to get a Troy Bilt string trimmer. Maybe not.

Any suggestion will be appreciated. thanks.............Raptor

Engine INTAKE AIR LEAK ?