Have a B and S 143 424152 on a Sears push mower. Won't start won't fire. Sometimes kicks back sometimes as tho it is firing prematurely (well before TDC) . Any ideas?
Engine runs fine on external fuel (propane) but won't stay running on its own once propane feed is removed. Initial problem was gas "peeing" out of hole on primer bulb hole. Cleaned carb and tested float valve initially with air pressure and then with gasoline with a tube and small funnel...
