Carb. on 883 sporster

Your description sounds likely an exhaust valve is leaking.

This actually sounds like an intake leak, most likely where the intake manifold meets the cylinder heads.

With it at idle, spray a little carb cleaner at the joint between the above mentioned two, and if the idle picks up, there's a leak.

This is common on Harleys, as over time, the rubber seals break down with the engine heat.

Ok, it sounds like you're either not getting fuel though the jets in the carb or you've got a bad vacuum leak. You said that you replaced all three "rubbers" on the intake. I'm assuming you're talking about the intake manifold gaskets and the carburetor seal on the opening of the intake. When you put the air filter backing plate back on the carb, did you have to lift or push down on the carb to get the three small screws or the two large bolts into alignment with their respective holes? If so, you didn't have your intake properly aligned and your engine is probably sucking air at the carburetor seal on the opening of the intake. Loosen the four bolts that hold the intake onto the heads and allow it to align itself with the air filter and carb. Then retighten the bolts. This should work. If not, I'd replace them again. Do not tighten the bolts until you insert the carb and bolt the air filter backing plate up to align the intake. Once you've done this and tightened the four bolts, you can take the backing plate back off and finish connecting the carb. Harley makes a "tool" for doing this. It has three studs that stick into the three holes on the front of the carb and the bolts that hold the backing plate to the heads. It holds the intake in the proper position while you tighten the four bolts on the intake flanges. You can do the same thing with the carb like I've described here but it's a bit more work. The choke on your carb is actually an "enricher" circuit. When open, it draws fuel directly from the float bowl, not through the jets. If the carb won't idle without the "choke" on, it's not getting fuel through the idle circuit. Turn the idle mixture screw in until it lightly bottoms then back it back out three turns. Start from there.

Good Luck
Steve

Hello
I would start with the easy less expensive stuff first.
Check/Replace your spark plugs. Carbon fouled, sooty plugs don't like to idle.
Clean/Change your airfilter. Dirty air filters choke the motor. choked motors either stall or rev high.
Carburetor idle screw needs set.
that is adjusted after the bike is warmed up to operating temperature, then set idle.
If that doesn't have you cleared up then you'll need to have your carbs cleaned.

Have a great weekend
Big Al

First I would start with the fuel filter, was that replaced too?, then I would make sure you have fresh gas and a new spark plug, Probably what I would suggest next is to pull your carb off and take apart and clean it with carb cleaner, most likely you will find dirt and possible small fragments from rotten fuel lines,partially plugging the inlet screen in carb, also your diaphram could be stretched, wouldn't hurt to pur carb kit in it while it is apart, I have just cleaned them before and been o.k. this should help you out

Black smoke indicates that your mixture is way too rich. Now, you didn't say what carb you're running, stock or aftermarket. But, what it sounds like to me is the needle and seat in the carb is leaking fuel and overfilling the float bowl. When you're running down the road, you'll using enough fuel so that the float bowl does not overfill. When idling, you don't use as much fuel, the bowl overfills, and fuel flows into the carb creating a very rich mixture. Is you overflow hose that connects to the bottom of the float bowl connected, clear and open? If so, turn the petcock on without the engine running. If the overflow is clear and the needle valve is leaking, you should see fuel start to flow out of the overflow hose. This is very important that it do this. If the overflow hose is blocked and you forget to turn your petcock off, you could wind up with a couple of gallons of fuel in your engine. It will leak out of the float bowl, into the carb past the intake valves, past the rings and into the engine. I've also seen it get into the primary drive case as well. I'd put a new needle in the carb and check the float setting according to the book. it's sets with the carb on an angle if the carb is the original Keihin CV.

Good Luck
Steve

Your Float bowl is stuck. Sometimes it gets a bi of dirt in it and keeps it from seating to turn off the fuel. You need to remove the bottom of the float bowl. This is easiest done by removeing the carb from the bike because you have 4 screws to undo on the float bowl. Really is pretty easy to do.

try spraying a little starting fluid on the intake manifold when the bioke is fully warmed up. be sure not to spray the starting fluid in the back of the air box. if the rpms change when you do this then you have an intake leak.

sounds like you you have bad gas and a air leak

The pilot jet controls the air/gas fuel mix at idle . If the jet gets plugged up not enough gas gets to the emgine at idle. You will need to remove the carbs and float bowls and clean them, paying special attention to the pilot valve. Count the number of turns to remove the pilot screw and replace the same number of turns then turn counter clockwise 1/2 turn.

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