Sluggish performance at 3/4 tank of fuel - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 4 (permalink) Old 07-31-2007, 02:01 PM Thread Starter
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Sluggish performance at 3/4 tank of fuel

Okay...I am completely freakin stumped here. My wife's bike has an odd problem. It runs flawlessly on a full tank of gas. As soon as there is about 35-37 miles used on the tank it starts running like crap as if it were starving for fuel.

I've seafoamed it, drained it, refilled with fresh, pulled and cleaned the petcock...everything I can think of. Once it's running like ass I can refill the tank to full and it runs fine. It seem obvious to me that it's a fuel delivery issue but where? I can't really think of anything left to check. Any ideas?
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post #2 of 4 (permalink) Old 07-31-2007, 02:24 PM
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After it's running bad, have you tried just popping the gas cap open, then close it, to see how it runs?
Might be a plugged vent line and the negative pressure in the tank is restricting the normal flow of gas.


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post #3 of 4 (permalink) Old 07-31-2007, 04:55 PM Thread Starter
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Yep I have, no change. About all i got left as a possibility is weak vacuum acting on the diaphragm in the pet cock.
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post #4 of 4 (permalink) Old 07-31-2007, 05:11 PM
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My bike's been doing the same (though at 80 miles rather than 30) - I'm agreeing with poor vacuum. Definitely post if you figure out what's up.

I've tried everything you have - one tip for now (if it works for your bike too) is when the bike starts running like ass play with the petcock some - usually gets my bike back to running right (I do have prime - you might not).

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