Having trouble getting them to start. I was in a hurry and bought some off brand 2 cycle oil and ran great for a week and now cant get them to start. 1 took muffle screen out 2 put new gas and oil mix 3 clean spark plug but are old got one to start one day but now i cant. Is it possible that the both spark plugs are fould out now. the one i got started i put that spark plug in the other one and woudlnt start put it back in the first one and started used it for a day but now they both wont start. Do you guys have any idea what it is?