I have a 1980 cb750c. When I got it, it wouldn´t open up good so I took the carbs apart and cleaned them. Now it opens up but it backfires on the right side. It also wont hold an idle without the choke being on. I have tried the airflow screw but it didnt get any better. I checked the spark plug gap and it was right. Does anyone have any helpful ideas because I am fresh out. Thanks