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'79 bouncing idle. I'VE TRIED EVERYTHING (kinda)

Discussion in 'The Garage' started by JessJGMiller, Mar 19, 2020.

  1. JessJGMiller

    JessJGMiller XS400 New Member

    So this has been a year and a half worth of trying to figure out what is wrong with my bike. I bought this fully running about 3 years ago I think, and rode it around with no problems for about a year and a half.

    Here's my problem now: My idle will bounce around a bit and "searches." After running for a little while the idle will rev or stall, or pulse. No telling which one it will do. It's always random. Sometimes after I rev it it comes back down to idle fine, and sometimes it comes down slowly. When I coast to a stop while riding it will die on me every time unless I keep giving it gas. Riding isn't a problem, but I want this to run right. A lot of what I have read suggests it's running lean, but I have pulled my plugs and they were black as can be.

    Here's what I've done: Carbs have come off and been cleaned like 50 times. There is no blocked pathways, good looking jets, etc. I have replaced the carbs and cleaned those multiple times. I have replaced and checked the floats, I have made sure there are sealed gaskets, I have adjusted mixture screws. I have replaced the boot intakes between the carbs and the engine to ensure there is no air leak. I have replaced the spark plugs multiple times, and I recently adjusted the mixtures until the end of my plugs were more of a golden color (indicating a good mixture). I have gotten new air filters and changed the oil, and I have replaced the filter in the fuel line. I have cleaned the inside of the tank out to make sure I wasn't getting a plugged petcock. Nothing should be wrong mixture wise or with fuel delivery at this points since I have changed out so much and continue to get the same exact problem. I have checked the coils with a meter but didn't really understand my results.

    My next plans once I get the chance are to take out the engine and check the valve clearance and just to make sure everything is working properly in there.

    Any ideas?? Please help. This has been going on for a year and a half and it's so incredibly defeating. I have been close to selling it multiple times.
  2. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    Next up: valve clearance and then sync the carbs. Id want to be sure of timing also to make sure its fully advancing.
  3. xschris

    xschris a lifestyle not a trend Top Contributor

    Post some pics of the bike so we can see your setup.
  4. JessJGMiller

    JessJGMiller XS400 New Member

    What kind of pics are you looking for?
  5. xschris

    xschris a lifestyle not a trend Top Contributor

    Of the overall bike.

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