pull cord jamming on honda izy ?

We have a Honda Izy lawn mower. The pull cord is jamming - I'm not sure if this is something to do with the pull cord spring, or a problem with the brake release. I've tried to unscrew the cover to have a look at the cord but having a little trouble unscrewing the bolts... but presumably I should be able to take the top off and check the cord.
I can see a small plastic white piece stopping the mechanism inside.
I took the mower to be fixed last year for the same problem but keen to try and do it myself to save money!
Thanks for any help or advice.