Cap blew off of this while trying to start up my KZ650 on full choke. Lots of backfiring out the pipes as well. Hints?? Previous owner put pods and a stage 2 jets kit FYI

https://i.redd.it/k426hlaludu31.png via /r/CafeRacers https://www.reddit.com/r/CafeRacers/comments/dm8hki/cap_blew_off_of_this_while_trying_to_start_up_my/?utm_source=ifttt