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Hey Guys! I just purchased a set of Sampson Big Guns 3 Ripsaw pipes for my 04 Dyna Wideglide it has a K & N air filter if this matters. Was wondering if anyone knows what size jet I might need or if re-jetting will be necessary?
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One size bigger slow jet. Leave the main jet alone. Cut 2 coils off of the slide return spring. Pull the plug on the idle jet and set the idle 2 to 2 1/2 turns out from bottom and replace the stock needle with a needle from a 1988 Sportster 1200.
As you can see from the responses so far, there are many "methods" to tune a carburetor. The main thing, for any carburetor and any pipe/intake/cam/head combination, is that the fuel air mixture is correct throughout the entire range of the throttle. It's best done with an exhaust gas analyzer, but you can certainly tune at home without one. My point is that there is no universal jet size or needle size for any given combination. Some people cut the spring, and some do not. The spring has nothing to do with fuel/air mixture, but with throttle response. You can get some surging if the spring is too weak. There are rules of thumb, and suggested starting points, but each combo might be a little different. The other "myth" is that for any given change, you will need to increase the jet size. I've tuned many bikes that ran better with smaller than factory main jets. Some bikes work best with a 42 (stock) slow and some with a 45. You just have to experiment if you don't have tuning equipment. Go to the Mikuni website and download their tuning manual. Even though you don't have a Mikuni, the tuning methods and principals are the same for your Keihin.
To answer your question directly, yes, your carb could probably use some fine tuning, but so could most all totally stock bikes.
Telltale signs that you need carb tuning:
Popping/backfiring through the carburetor. (Lean)
Hard starting. (Lean)
Slow warm up (needs choke for a long time). (Lean)
Poor gas mileage. (Rich)
Abnormally high gas mileage. (Lean)
White spark plugs. (Lean)
Sooty black spark plugs. (Rich)
Sooty black exhaust smoke. (Rich)
Re-jet carb
