I'll start with the question: How do I fix this? Bike idles, rides, but the carb pops and backfires with increase in RPMs. I read that it may be vacuum lines? The bike is an 2002 Sportster 1200 C. Original carb, fuel lines, and hoses. A lot of the rubber is cracking and obviously needs to be replaced. I have the mechanical manual-- do I just order all new fuel lines and hose? No clue on this one?

Long story, familiar story I am sure... Loved to ride all the time, got married, baby came along, and so there the bike sits in the garage. Would love to take it out without having the popping jerking and stopping going on. Help would greatly appreciate.

 

Back firing from the carb indicates a lean fuel mixture. Nothing to do with fuel lines. Check manifold gaskets and carb gasket with wd40. Spray around gaskets while engine is at idle and listen for a RPM change. If it does then change which ever gasket caused the change.

If no change than you will have to give the low speed needle a 1/16 turn open. (Also called the Idle jet)

Since it appears the problem has been with the bike awhile and it happens on acceleration, guessing it is the spigot gasket that is split on the inside. This is the gasket that connects the carb to the manifold. The more it backfires the worst the gasket will get.

 

Like Kabear said:
"If no change than you will have to give the low speed needle a 1/16 turn open. (Also called the Idle jet)"
For "popping" on deceleration when there's no leaks anywhere, that should do it. Might take a bit more than 1/16th of a turn.

 

Do what Kabear has suggested for sure but if the bike has been sitting in the garage for an extended period, pull the carb and give it a thorough cleaning to make sure all orifices are open, diaphragm is in good condition, etc.

 

This is fantastic, simple and concise advice. Now I know who to message with my carb issues!

 

Might also have to increase the low idle screw.
After my cam upgrade I had carburetor popping on deceleration, changed all 3 manifold gaskets but it didn't help. I only got red of it by upping the idle to 1100RPM warm.

 

Here are the rules for a HD, if it pops through the carburetor its timing. If it pops through the exhaust its carbonation.

 

Since ya got a baby......been there,spend an hr every day doing something on your bike n soon it won't need anything but ridden. Adress all the old and cracking rubber any seals carb to manifold,manifold to heads. My bike was acting up n a similar manner when I bought it n it was a combo of air/fuel and the enricher (choke) was loaded up w carbon. Good luck

 

Some real sound advice here. Only thing I would add is make sure you are running fresh fuel. If it's been sitting awhile, it could've gone bad.