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2003 Sportster LX running bad


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Hi, i am new to the forum. Ive searched around here for answers and come to the conclusion that i think my problem is in the carb. I have the Indmar 310 carb motor. It has 450 hours on it. I have replaced the plugs, cap and rotor and checked the timing. The boat doesn't want to idle, runs lumpy when going slow (like no wake speed) and stumbles when taking off. Mid and upper it runs great and runs right up to 5100 RPM with no issues.

A couple questions. Any one else think its a carb issue? If so what Holley model # carb is it. I tried looking at their site for a rebuild kit but i must not have written down the right #s.

Any help would be and is Appreciated

Kris

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skidim.com has rebuilt kits for that carb.

Is the fuel fresh and the filter recent?

-Chris

Fuel is fresh. Filter was replaced last summer

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Oh, the #s i have off the carb are ( i think i must have missed a #???)

Holley P-80

6R80025

Front float bowl had a 10928

5

2nd ary had a 11166

Top of front float 120(7 or a 2)34

Going from the link above is the carb a 4160? or 50?

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I had the same problem with my sportster.... After new plugs, fuel filter, fuel lines, cap, rotor, plug wires..... it ended up being a short in my electrical system.

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I had the same problem with my sportster.... After new plugs, fuel filter, fuel lines, cap, rotor, plug wires..... it ended up being a short in my electrical system.

So yours ran bad at idle but fine up top? What exactly was your electrical issue?

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  • 11 months later...

Ok, well the problem wasnt the carb. Shortly after posting this i noticed the oil getting milky. I noticed the intake mani bolts were hand tight. I pulled the heads off and had them checked for being warped they were fine. I put a new set of head gaskets on it and new intake mani gaskets and the boat ran great, for a while. Then when winterizing it i noticed milky oil again. So this spring i pulled the heads off again, put new gaskets on, replaced the head bolts and all was good for 2 months now and today it happened again! Any ideas? Why does it work fine for a while then act up? Is it time for a complete rebuild?

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Ok, well the problem wasnt the carb. Shortly after posting this i noticed the oil getting milky. I noticed the intake mani bolts were hand tight. I pulled the heads off and had them checked for being warped they were fine. I put a new set of head gaskets on it and new intake mani gaskets and the boat ran great, for a while. Then when winterizing it i noticed milky oil again. So this spring i pulled the heads off again, put new gaskets on, replaced the head bolts and all was good for 2 months now and today it happened again! Any ideas? Why does it work fine for a while then act up? Is it time for a complete rebuild?

You need a new torque wrench :rofl:

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nope, it was just re-calibrated recently :)

I have been looking around and many places are leaning towards the exhaust risers? Any one think it might be them causing the issues?

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nope, it was just re-calibrated recently :)

I have been looking around and many places are leaning towards the exhaust risers? Any one think it might be them causing the issues?

It could be the exhaust mani or riser. When you take the heads off you can often tell where the water is coming from. If it's the exhaust risers then it will be draining back through the cylinders and you can look for evidence of that. Leaks from the intake mani or its gasket will usually leak into the middle of the block. The fact that your intake bolts came loose at least once makes me want to look there for the problem. You had problems running at idle and low speed which also points to intake mani leaks rather than exhaust and riser. Ethanol is taking its toll on older boats and many gaskets can become too stiff or dry to do their job. Just some thoughts.

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