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Retired Firefighter
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Discussion Starter · #1 ·
I have a 2003 Dyna Low which seems to be running lousy and won't hold a consistent throttle speed. Okay at idle and runs good at 3000 RPM's but hesitates and sputters at anything below 3000 or above idle. I purchased this bike used this spring with 40K and not very familiar with carburated engines, however I have pulled the plugs and they are very fouled (black soot) and replaced them, but I doubt that's the solution. I also wonder if the jets are correct as this bike has Screaming Eagle pipes, so thinking the carburator was never set for the reduced backflow/compression. Am I on the right path, or should I be looking somewhere else for the fouled plugs? I am leary of running this bike too long or too far for fear of damaging/ruining the engine since it has so many miles on it.
 

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Hit it she goes boom
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Yup, black soot on the plugs and/or black smoke are signs of running too rich, your on the right path. But before you go digging into the jetting and such, give it a good cleaning, there might be some varnish gunking it up. You can't really hurt the engine unless your running so rich your getting gas in the crankcase. Pull the dipstick check for a gas smell. I'd rebuild the carb then go from there. Just my .02
 

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Retired Firefighter
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Discussion Starter · #3 ·
Thank You! I was curious though, as to which or what you recommend to clean the carb up with? Should I just use the carb cleaning kit from the auto parts store that comes in a paint type can where one can immerse the carburator in a solution? If this does not resolve the issue, should I then get a stage 1 rebuild kit? Also, what size jets should I get if this is where I end up if all else fails? I had thought about taking this to the dealer or repair shop, however, aside from the cost, I really want to be more hands-on with my purchase. Not like my automobile, which has so many parts/sensors that I am almost afraid to check the oil!
 

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Before you start working on the carb, check the air filter. If it is filthy then you are not getting enough air and will be running too rich. Also you might have an add on that makes it run rich if you have O2 sensors in a closed loop. But, check the air filter first. If the carbs are dirty and jets clogged then you would be running too lean. Also if you have O2 sensors and one or both are bad, that will make the bike run rich.
 

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Retired Firefighter
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Discussion Starter · #5 ·
Good advise, and I have checked. Filter appears clean, can see light through it, but I will pick up a new one. Trouble is that once I pulled the cover and filter off, there was a strong odor of gasoline. Upon further examination, I noticed that there was a trail of residue from the side of the carburetor onto the air filter housing and down the side where it has collected on the filter itself. Is this normal or common?
 

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First off... you don't have O2 sensors with a carb .

The line of "residue" is most likely just the oil mist that collects from the head breathers . It's normal .

Before you take anything apart, try this first : Run two or three tanks of fuel with a heavy mix of SeaFoam in it . It'll clean the internals of the carb if it's not too gummed up .


:biker:
 

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Retired Firefighter
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Discussion Starter · #7 ·
quick and easy solution! Thanks, I will give that a try first, but that means I have to ride a bunch to go through that much gas, oh darn it!
 

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First off... you don't have O2 sensors with a carb .

The line of "residue" is most likely just the oil mist that collects from the head breathers . It's normal .

Before you take anything apart, try this first : Run two or three tanks of fuel with a heavy mix of SeaFoam in it . It'll clean the internals of the carb if it's not too gummed up .


:biker:
That is very true. But, I don't know the exact setup on his bike. But it does not stand to reason that a dirty carb needing cleaning is going to put additional fuel into the system to make it run rich. It would be just the opposite. A dirt carb is going to restrict fuel flow.
But a dirty carb will cause a sputter and bogging on acceleration. Another thing that those plugs might be telling by being ugly black is burning of oil. I'd do a compression check.
 

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That is very true. But, I don't know the exact setup on his bike. But it does not stand to reason that a dirty carb needing cleaning is going to put additional fuel into the system to make it run rich. It would be just the opposite. A dirt carb is going to restrict fuel flow.
But a dirty carb will cause a sputter and bogging on acceleration. Another thing that those plugs might be telling by being ugly black is burning of oil. I'd do a compression check.
FWIW A stuck or sunk float could cause a over rich condition Maybe dirt or varnishing in the float bowl from sitting too long.

Jonathan
 

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FWIW A stuck or sunk float could cause a over rich condition Maybe dirt or varnishing in the float bowl from sitting too long.

Jonathan
And the cure would be to run a few tanks of fuel with a cleaning agent in it first, then if it does not clear up, tear into the carb .

I do believe we are on the same page . :thumb
 

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STAND AND FIGHT!
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IMHO, several of the the first theories are bass-ackwards,

--- open exhaust and carb maybe not adjusted for freer flow,

that would be suspect to cause a lean condition but not rich..

--- 40,000 is not nearly "a lot" of miles on that engine,

--- instead of being afraid to run it, I might suggest running the hell out of it,

if the midrange was enrichened, a lot of people would jet rich for power

and running easy might cause loading up the plugs. I don't add cleaners right away,

between alcohol and additives, today's tier one fuels have aggressive cleaners in them already,

complaints have to do with eating plastic or rubber parts, just try a few tanks thru it and see..

BTW, for anybody buying an older bike, please do check the date stamp on the tires.

Just because they have tread on them doesn't mean they're not too old to be

worthy of risking your life on. I would not want to ride the hell out of 10 year old tires

...
 
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I agree with bobf. Make sure the choke is adjusted correctly. That was the first thing I thought when reading your post.
 
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