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Help me diagnose my lean condition

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    #1

    Help me diagnose my lean condition

    Ok, I'm getting tired of this lean stuff.

    The only mod to the engine is the stock HD mufflers I put on the existing headers. They're unmodified, no baffle drilling, nothing like that. The airbox is stock and the filter is a UNI OE-style replacement foam filter. The stock filter on this bike is foam too, but was deteriorated.

    I've replaced the intake o-rings. The boots are soft and pliable. The carbs have been off and cleaned several times this year. I went up one mainjet size to 117.5. Backed the pilot screws out 1 turn to 2 1/2 turns.

    I had shimmed the needles (or thought I had). All cylinders but 4 were showing perfectly clean plugs. Not ashen, just new looking. 4 was a nice light brown.

    After reading some threads here on needle shimming, I realized that I hadn't done a thing cause the shims were in the wrong place. I fixed that, which put the needles 2mm higher than stock. I just took it for a test ride, and checked the plugs, hoping for the best. Well, cyls 1 2 and 3 were still clean as new. 4 was dark brown.

    I just dont get it, the mods to the bike are not at all extreme. It runs great, idles well, doesn't stumble anywhere in the throttle, cruises nicely.

    It's just the darned plug reads have me worried. Am I worrying about nothing?
    Tags: None
    #2
    Sounds like your carbs need to be dis assembled and soaked for a couple days. Or, the floats are not set to the correct height, or the carbs are quite a ways out of synch.

    Earl
    All the robots copy robots.

    Komorebi-The light filtering through the trees.

    You are free to choose, but you are not free from the consequences of your choices.

    Comment

      #3
      Well, the float level is correct.

      Sigh. I'll have to wait on the soaking bit until I can afford a can of carb dip and new o-rings for the disassembly.

      I don't have a quad manometer to do a real super accurate carb sync, but I did check each cylinder with a single damped vacuum gauge. All within 1 in/Hg, and it runs smooth, so its definitely not far out of sync.

      Comment

        #4
        117's might be to small, you may need to go bigger on the main jets. That exhaust is use to 600cc of power coming out of it on the exhaust stroke if it's off a 1200 as compared to 250cc from a 1000.
        1166cc 1/8 ET 6.09@111.88
        1166cc on NOS, 1/8 ET 5.70@122.85
        1395cc 1/8 ET 6.0051@114.39
        1395cc on NOS, 1/8 ET 5.71@113.98 "With a broken wrist pin too"
        01 Sporty 1/8 ET 7.70@92.28, 1/4 ET 12.03@111.82

        Comment

          #5
          Thanks for the tip Jake.

          And Earl, thank you for your advice as well. What I wonder about is why one cyl (#4) seems to be OK.

          Is it possible my exhaust valve clearances are too tight, and maybe its sucking air from the exhaust on the intake stroke? If I recall correctly, #4 came up with slightly different compression readings than the other 3 cylinders.

          Would it run like complete crap if I had ex. valves that badly off?

          Comment

            #6
            if your exhaust valves were'nt closing completely then you would have some power loss that is noticeable, perhaps not even run. (this due to your compression going straight out the valve)
            did you do a mechanical sync when you had your carbs out? that is one of the biggest issues with our carbs, even though youve done a vacuum sync if the butterflies are off then you can still get your lean condition

            Comment

              #7
              Ok, here's where I'm at with this-

              I 'shimmed' the needles to their max - by putting the plastic spacer UNDER the clip on the needle, and no shims on top of the clip. (previously I had two shims on top of the e-clip).

              Synced the carbs well with a Morgan Carbtune, and made sure to set the outside two carbs at 2cm higher vacuum than the inside cyls.

              So far, it looks to be burning nicely. We'll see this weekend when I go on a longer ride.

              Comment

                #8
                Hmm..

                I replaced my mains with 122.5's, and tried it out. Seemed to be the same - plugs white to greyish.

                Pulled off carb vent hoses. Started the bike, and there was a noticeable change in the odor to the exhaust. Took it out for a couple miles on the freeway, and it definitely runs different. Doesn't pull as hard in 5th from 60-70 (4.5-5krpm), but pulls much harder through the higher revs (> 6k).

                Now, I just hope it isn't too rich.

                Comment

                  #9
                  I'm basically running the same setup as you are: H-D FXS mufflers and a new Uni filter replacement foam element. My plugs were quite white as well. After a few days, they were more of a very light tan/grey color but still looked too lean.

                  Yesterday I replaced the foam sealing the end caps of my airbox, because it was nearly as bad as the old filter element. After making a 25 mile run and pulling my plugs, I found that they all had a darker tan appearance. Did you check your end cap seals?

                  FWIW,

                  Comment

                    #10
                    Ok, well, now it was too rich. I re-arranged my needle shim setup to go back to a stock needle setup. We'll see tomorrow after the commute.

                    There was a stumble on lower RPM roll-ons, and the plugs were mostly sooty.

                    Comment

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