2008 sportster 1200 backfire/stumbles

Discussion in 'Sportster Models' started by seabee, Dec 18, 2014.

  1. seabee

    seabee New Member

    so ive had my sportster for about 2 years now, other then normal maintenance i added the stage 1 screaming eagle tune and ive added taller handlebars, got a switch kit from harley so no soldering or anything, crimped pins to the connectors. only ridden 6 times in the last 5 months, and lately its been popping and missing, and backfiring, rough idle, it will idle on its own but will eventually die. first thing i did was replace the plugs and wires, and even replaced the intake gaskets going into the head. Still doesnt run right so need help on where to look and what to test now. i have the service manual but it just shows how to replace parts not troubleshoot them. the tune was done right after i bought it and ran great for 2 years until now,
  2. vonh12

    vonh12 Member

    Bad gas maybe?? Think I'd check the gas filter, clean the carb. and change out the gas, new air filter- all the basic tune-up things and go from there.
  3. dbmg

    dbmg Guest

    Is there more performance mods done that is not being discussed. Why the Stage 1 tune and no parts? I would think that you should be getting a check engine light. Have you checked for a vacuum leak at intake attachment to heads..
  4. Breeze3at

    Breeze3at Well-Known Member

    2008 = fuel injection. Could be clogged fuel filter, pin hole in fuel line in tank. etc. Listen for sound of pump priming when key is turned on, listen for "whooshing" sound of gas leak inside tank.
  5. gator508

    gator508 Well-Known Member

    Just dragged out my 07 sportster owners manual, and in addition to what is already mentioned, check your battery cables for tightness, or a discharged battery. Good luck!
  6. Dr. Dolittle

    Dr. Dolittle Experienced Member Contributor Retired Moderators

    These two statements lead me to agree with the suspicion of a gas problem. It's been well documented that the current gas makeup does not lend itself to sitting around in the tank for long periods unburned. Start with the simplest troubleshooting - completely drain the gas tank and refill it with fresh gas, maybe even adding some Seafoam also. If that doesn't help, I'd continue on with the other more time consuming and costly suggestions.
  7. Jeff Klarich

    Jeff Klarich Well-Known Member Contributor

    All good advice, this may be a hit and miss process. Before you start throwing money at it start with the basics. As gator508 suggested check battery and leads and if still having issues move to fuel.
  8. seabee

    seabee New Member

    thx guys, ill drain the tank and check the battery,
  9. Jack Klarich

    Jack Klarich Guest

  10. seabee

    seabee New Member

    no engine light on, i went to start it and the battery wasnt strong enough to turn it over, i charged it last week and now its at 11.98. if it wont turn the bike over after a week then im getting a new one and see if that helps anything.