Hey guys I am stumped on my Briggs and Stratton 5hp horizontal shaft tiller motor, I just finished rebuilding it, new valves, piston and rod, piston rings, new spark plug and gasket set, replaced the crank shaft with good used one. The motor will start and run if i keep it revved up a little but will not low idle and when I run it at higher speeds it runs dirty, its not a clean clear sound if you know what I mean, I have cleaned carburetor with carburetor cleaner, replaced needle and seat screwed out 1-1/2, new diaphragm kit with spring ring cap. The only thing I have not changed is the breather, I have it on order, should come in Saturday. Any one have any thoughts if the breather doesn't help. Model: 130202, Type: 0135-01, Code: 6701261. This is a 1967 motor.