speedfighter will start but wont rev up ?

i have 2 w reg water cooled speedfighters one was stolen recoverd but the ignition was ripped apart the other had a knackerd engine so iv swapped engines but the good engine has an extra wire coming from it it went to the ignition on the one i took it out of but iv tried that and it dont seem to make any differents the bike starts but you pull the throttle back and it only ticks over but its not ticking over smoothly iv checked the carb thats all ok can anyone advise me thanks shaun