Coughing and spluttering

Hi all help please we have a great camper but it's always coughing and spluttering and when slowing down it sometimes pops any ideas.It a 1973 westy with a 1.7 twin carb engine.Thank you Gary.

 

dirty fuel lines/filter blocked jets/dirty carb also timing...... could be any or all of the above.

 

if it pops when it slows down, that's an air leak on the exhaust...

when was the last time it had a service, including tappet gaps?

 

Thank you for your replies it had a small service about 7 months ago and the tappits were done then.

 

Is it coughing back up the carbs too?