Harley Road King Classic 2001 exhaust trooble shooting?

I have a Harley Davidson Road King classic 2001 that it has Magneti-Marelli FI. Only mods. are screaming eagle slip on mufflers, Arlen Ness big sucker2 air cleaner kit, and Arlen Ness big shot fuel tuner. I programed the tuner, seems to run best on the preset map settings already loaded. However, when I accelerate hard then let off and let motor idle down, every so often the exhaust pops. It is a loud pop, not the normal kackle. It is not a cough or sneeze through the breather. What could be causing this? I have tried the program in several modes but they all do this. Have also tried less fuel. I do not have an exhaust leek.

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  • 1 decade ago
    Favorite Answer

    ACTUALLY.......exhaust backfire on decel can be caused by lean OR rich!!!!....USUALLY on injection, it's caused by rich (too much gas at 0% throttle position) , carbs by rich also ( high manifold vacuum pulling too much fuel through the idle ports), although, too lean can cause this also (lean mis-fire leading to raw fuel through the exhaust that get ignited by internal pipe heat and cold air from exhaust reversion hitting each other), it has alot to to with the total engine combination, exhaust length and diameter and cam overlap and igniton timing.

    I don't mean to sound insulting, but you WASTED your money on the Ness Fuel controller, you SHOULD have gotten a Power Commander....ALWAYS go with products from a campany that SPECIALIZES in what they sell!!!....Power Commander III USB with Acellerator Pump Feature is the industry standard (for almost everything except HD Delphi, PC 5 with wide band O2 sensors for Delphi), even better, is HD's Super Tuner (for the newer Delphi System). With a Power Commander and a DYNO, you can dial in the injection PERFECTLY....with your situation, lean out the air/fuel ratio at 0% throttle from 1000-3000 rpm (approx, each engine is individual).

    The best thing I can tell you to try is to lean out the LOW RANGE one step at a time until the exhausti popping stops. If it won't stop by leaning it out, you may have the rare case of actually being too lean as Adam said, try richening one step at a time....but I will lay odds on the fact that you are actually rich....HD's Super Tuner has a feature to lean out the a/f ratio at an already predetermined rpm range and throttle position, on the Power Commander, you have to manually change each cell of the map individually.

    ALSO....EXTREMELY IMPORTANT!!!!........

    In order for ANY adjustments to be CORRECT, you will HAVE to verify not only no exhuast leaks( as you state you don't have), you MUST verify no INTAKE leaks...AND....you MUST have the THROTTLE POSITION SENSOR "ZEROED"!!!!!!!......unfortunately HD is the best place for the TPS....they can do it in a matter of a few minutes....it REQUIRES special equipment.

    Source(s): 20yr HD Tech. MMI Grad 1991 and 2009. Factory trained by HD (Buell Certified), Big Dog, American Ironhorse, Titan, and Indian
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  • 1 decade ago

    v twin is correct, overly lean mixes can cause backfiring as well. Lean mixtures burn slower, meaning that a very lean mix hasn't burned completely when it's pushed out the exhaust, where it completes its combustion. I've seldom had overly rich mixes backfire though. Try running with a true choke on (not the enriching circuit carbs) and you'll see what I mean.

    If the bike runs well otherwise, starts easily, doesn't surge under light throttle and gets acceptable fuel economy, I wouldn't worry about it. You have to keep in mind that the factory equipped mufflers have metal baffles and are not of straight through design, so you could of had some small backfires before you made the modifications but just couldn't hear them very well.

    The reason I say to not worry about it is because you could spend hours and hours and countless dollars and not make it any better, or even make it worse as long as you use the existing components. Replacing parts is going to be very expensive and if the only benefit is the reduction of what is now an occasional backfire, it may not be financially worth it. If it only does it on hard decelleration, just accept that as a tradeoff for what other benefits you got when you made the changes. With engines, you never get something for nothing. It's like a teeter totter, what you gain in one area, you lose somewhere else.

    Now if you're filthy rich and sleep on a mattress stuffed with C notes, then ignore what I just said and start changing parts.

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  • Kristi
    Lv 4
    4 years ago

    You really oughta consider taking it to an experienced mechanic and checking into a Power Commander. If I wouldn't have been fired I would've done it on my 2005 Harley Road King at work, but I had a feeling the Chief of Police would've been ticked off. Everybody I know with a Power Commander raves about the power, check it out with some people, I don't think you'll be disappointed. Any mods and exhausts changes you make will be better with this add-on too in my humble opinion.

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  • 1 decade ago

    Back fire in the exhaust means you are running rich. What happens is unburned fuel passes the combustion chamber into the hot exhaust chamber and ignites there. I am not familiar with your carburetion set up but it is running rich, most likely on the top end circuit.

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  • Bob A
    Lv 7
    1 decade ago

    Bradley B is correct as to over fuelling.Since you have a FI system three things tat cause over fuelling are Map sensor,TPS or O2 sensor out of range .Find the manual for your system it should have trouble shooting guides in it.

    Source(s): 35 yrs lic mech 40+ yrs riding
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  • ?
    Lv 4
    1 decade ago

    actually a backfire when you let off the throttle means you are running LEAN. Since your bike is fuel injected have a qualified tech diagnose and set it up for you.

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