i am sure you have checked, but be sure the air filter is clean and not soaked in oil. next is to check your fuel filter and make sure there is not any debris clogging it, as a bad fuel filter is this exact same symptom. also check the battery terminals to ensure they are tight and clean. let us know if these check out okay. also inspect the spark plug cap where it attatches to the ignition coil wire, and you may need to trim the coil wire slightly to ensure the cap has a good connection with the wire inside. also check the plug cap with an ohm meter, which should measure about 4k ohms.