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*Poor Performance With Carb Models


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A lot of owners of Harley's that run carburetors have asked a question about poor performance, especially at the upper RPM ranges. The symptoms are that it is starving for fuel and will not accelerate past mid range or a bit higher.

The usual cause for this type of problem is a build up of sediment and scale from the fuel and the tank itself that will partially cover the main jet in the carburetor which sits at the lowest point in the float bowl.

This diagram will show you where the different circuits in a carb take over from each other. As you can see, the main jet starts flowing fuel just below 1/2 throttle. This is when your fuel will start to lean out if you have the buildup of sediment in the float bowl.


To drain the float bowl without disassembling anything, this is how to go about it.

If you look at the bottom of the float bowl viewed from the horn side of the bike between the cylinders, there is a small brass screw there. Take a long thin screwdriver and open it up a turn or two. This will purge the float bowl right below the high speed jet at the lowest point in the carb. The fuel will come out a drain tube in front of the rear wheel so you may want to do this outside. Make sure you have the petcock opened when you do this so the rush of fuel from the tank will help clean the bowl out.
Run a few ounces out and repeat this again, then try the bike again at speeds to see if it solved the problem. I would open and seat the screw lightly a few times when you are done to make sure it is flushed and no debris is in the seat of the drain screw.

Here's a pic of what you are looking for. It will give you an idea seen at the bottom most area of this pic.

It's wouldn't be a bad thing to do at each oil change to keep the carb clean.

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I opened mine up but did not see any fuel come out anywhere. I turned the petcock a few times, opened the tank cap, cranked the throttle a bunch as I see it squirting, even ran bike with it open 3 to 4 turns and didnt get anything, my problem is bike starts fine in low revs any real twist bogs it down to nothing, also had several limp home in spurts episodes, I can twist a wrech but not sure I should try to pull carb off for clean out or if I can I would probably just replace the jets that are in it as I am trading it in. its a 2000 only has 7K miles supposedly, seems easy to just change speedo. Guy before me has already been thru a coil. If it is original miles, obvious it sat good bit, ran pretty good and fast when I got it, problems after pushing it a bit, then running low/out of fuel. Glad guys like you are out here. Ballpark on dealer pulling it cleaning, new jets and rebuild kit? Really kinda went south today hours after I made deal to trade it. Of course. AJ
Mr. Data: Have drained the float bowl 3 times on 1995 Ultra with 75000 miles due to intermittent bucking and smothering. Each time fewer black and sand- colored specks. Of course has been running too rich and plugs fouling. Seems to be improving-need another run or two to really know. Any thoughts re where specks coming from be appreciated. Thank you. Murph.
Murph,you probably have sediment in the tank,remove it ,drain it and flush it out.
Steve: Thank you for the info. Is there a commonly available product that I can add to the gas to avoid this in future? MURPH
Nothing will prevent sediment but sea foam or marvel mystery oil will clean any varnish deposits left by fuel in the system.
Mr. Data:
been following your notes on hesitation issues, what about a fully open throttle under highway conditions but only getting 3200 rpm's and 65 mph on a '94 Ultra Classic Tour Glide. No hesitation and engine runs strong. This just happened today.
Set any codes? It should do more than that. Try draining out the float bowl a few times then re test it.
ok I will. unrelated question: how do I get a picture of my ride to show when I make a post? I have a good one in my profile.