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New carb. or not?


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Hey, I have a Holley 4010 on my 1999 sportster that I have rebuilt, but it is still acting up. The secondaries are not opening, even after installing the lightest spring I could get from Holley. I have heard that these carbs. are not good and should be replaced with either a 4150 or a 4160.

2 questions: Am I wasting time and money trying to get this 4010 to work and tune properly?

And if yes, which Carb. is the best for a sportster?

Thanks.

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I think the Eldebrock 1409 is the exact replacement.

What type of choke do you have?  I have an original Weber that has the manifold choke that I could donate, it could use a rebuild and needs the jets installed.

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15 hours ago, lanshark said:

Hey, I have a Holley 4010 on my 1999 sportster that I have rebuilt, but it is still acting up. The secondaries are not opening, even after installing the lightest spring I could get from Holley. I have heard that these carbs. are not good and should be replaced with either a 4150 or a 4160.

2 questions: Am I wasting time and money trying to get this 4010 to work and tune properly?

And if yes, which Carb. is the best for a sportster?

Thanks.

You didn't provide a lot of background, so did it work before, and has recently started underperforming?  Is the engine hesitating or lugging?

How do you know the secondaries are not opening?  The air breather should be on when tuning secondaries since it affects vacuum.  The best trick I have heard to see if they are opening is to put a paperclip on the secondary shaft, slide it up against the housing, and test drive.  If the secondaries have opened, the paper clip won't be against the housing any more.

The secondaries probably won't open if you are juicing the engine in neutral and watching.

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@lanshark Did you replace the secondary diaphragm too? My 99 Sportster has the 4150 and I was having a similar problem - secondaries weren't opening all the way. New diaphragm fixed it - noticeable difference.

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I replaced the diaphragm when I rebuilt it. I bought the boat with it only turning around 3800 to 4000 rpm. I have replaced plugs, rotor, cap, plug wires, bought new prop. When I am running it on the lake wide open the secondaries are not opening, I can slowly open them by pushing on the rod to the diaphragm and the RPM's increase as does the speed. I have not heard of the air breather being a factor, but it does make sense. But with the air breather on and running wide open, it still only gets 3800 to 4000 RPM's. So that is the same as with the secondaries not opening. I have heard the 4160 is a much more reliable carb.

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7 hours ago, lanshark said:

I replaced the diaphragm when I rebuilt it. I bought the boat with it only turning around 3800 to 4000 rpm. I have replaced plugs, rotor, cap, plug wires, bought new prop. When I am running it on the lake wide open the secondaries are not opening, I can slowly open them by pushing on the rod to the diaphragm and the RPM's increase as does the speed. I have not heard of the air breather being a factor, but it does make sense. But with the air breather on and running wide open, it still only gets 3800 to 4000 RPM's. So that is the same as with the secondaries not opening. I have heard the 4160 is a much more reliable carb.

I guess it doesn't really make sense that they won't open under those conditions.  Maybe you have a vacuum leak; it might be worth putting a gauge on the manifold and taking a look.

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Also any reason there is the 4010 model carb on there vs the 4150 that came stock?  Seems it has been changed out at some point.

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