having some trouble with the .28. when I try to lean it , it will take off but when it reaches its upper rpms it shuts down like it ran out of fuel but its blowing lots of smoke all the time like it way rich also is blubbery . if I just leave it rich and not try to lean it it wont shut down but it never reaches rpm and has no power. do you think it still needs more breakin time as there is still some resistance at the top with the plug out?