Not running right

If the spark plugs are black, it is running rich, end of story, you are dumping too much fuel. You need someone that can do carb tuning on the bike. There is help in the Volusia Forums and it appears to be a known issue..

https://www.google.com/search?q=2004+Suzuki+Intruder+VL1500+running+rich

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Carbs running rich.. choke still on (jammed)
The carbs likely need a rebuild or a good cleaning.. try running SEAFOAM through the fuel system for a few tanks

Sounds like the carb needs cleaning, it's running too rich. First check the choke cable is not broken and travels full range.

if carbs are clean and not flooding etc then try finding out which cyls are off then swop plug caps over from good cyls and see if problem moves , if yes then fit a set of 4 new plug caps ! if no then do carbs again !!

Set flats at neutral to closed just below bowl height. Run mixture screw all way in by hand. Back out 2.5 rounds. Start and observe exhaust. Smells rich turn screw in 1/8 at a time

Odds are that you need to richen up your carb. You said that you can smell that the mixture is very rich. This is true if you're using the enricher. The enricher is designed to be very rich and it will foul plugs if you allow it to run too long. I usually run it only long enough to allow me to set the throttle lock and keep the bike running at a high idle without the enricher.

To actually remedy the problem and shorten the time you have to run the enricher, you probably need to enriched the low speed jet. The carb comes jetted very lean from the factory and usually does a lot of coughing and spitting out of the carb. If your slow speed jet is a #45, you need to go to either a #48 or a #50 slow jet.

Good luck
steve

That may be to keep dirt out. One of the screws should be for the richness setting and the other for the idle speed.
Adjust the richness setting so the tool runs the best (fast) then turn the idle speed down to normal.
Make sure you always keep the air filter cleaned or dirt will get into the carb and cause you to have to clean out the jets in the carb.

Try a scan, you may have bad o2 sensors which can make it run rich.

Another problem could be a fuel injector that is leaking. You have to remove the plugs one at a time an look at the ignitor see if there is fuel on it to know which injector is leaking.

There can also be problems with idle air controls or even the main computer, but start with the scan. Most Advance and Autozones will do it for free.

Hope this helps.

Check the fuel filter, it might be clogged.