unlikly exhaust agree with others fuel problem most likely,turn engine over and spray carb cleaner in intake,if it tries to run you have not enough fuel.pump?lines/filter.it is possible to gravity feed the carb via the fuel inlet pipe as a more accurate test,small funnel on inlet withfuel can lid of fuel ,becareful of spitback and keep excess ful away as fires can start,if it not fuel its spark or timing ie belt slip...good luck phil 07957617548