My 2003 Sportster 1200 just started a problem...hard to start, when i do get it started the rear cylinder doesnt seem to be running...cold exhaust comes out and there is not the normal vroom. Front cylinder seems to be running fine. Choke has to be pulled out all the way. After a minute or two the rear cylinder begins to fire and occasionally backfires. Even when warmed up i have to leave the choke pulled out and rear cylinder backfires every few seconds. Carb cleaner and "sea foam" brand cleaner dont seem to be working. Fresh gas in bike. I have never pulled this carb off. What do i need to do/check before i start taking the carb apart?

 

Sounds as the rear cylinder is lean. Vacum leak between carb and rear cylinder head.

 

Ditto. Also, have you checked the sparkplug and/or wire, ignition coil, and module? Could be an electrical problem.

 

Checked the spark plugs and they are about 3 months old. gap was good but they were both a little wet, even the cylinder that was running correctly. Will check those other items tomorrow.

 

Plugs do fail....but buy a service manual for your bike and do some serious mait. on the bike. Plus the HD service manual has great trouble shooting guides in it. Plus some good advice was posted above.

This place will help you tune your carb.

Harley Davidson Performance Tech Tips