Replaced leaky petcock, now it doesn't run right. - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 14 (permalink) Old 06-15-2017, 09:52 PM Thread Starter
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Replaced leaky petcock, now it doesn't run right.

I have a 2003 Vulcan with about 2800 miles on it. Been siting for years. Got it running good. Ear shave and coasters done. Ran with no problem for the past week, except the petcock had a small leak. Installed new petcock today. Now it seems to have an oscillating hesitation. Runs good, then boggs for a second, then runs good, and boggs, then runs good, and boggs......

No more leaking though. The petcock is new OEM.

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post #2 of 14 (permalink) Old 06-16-2017, 10:07 AM Thread Starter
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I'm thinking the new petcock diaphragm could be stuck? Who knows how long it's been sitting on a shelf somewhere.
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post #3 of 14 (permalink) Old 06-16-2017, 10:30 AM
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Yes sounds like it's not flowing fuel properly. You can check this by running two fuel lines from the petcock into a jar, and then applying some suction to the vacuum line.
You can use your mouth or one of these:
https://www.walmart.com/ip/Bulb-Syri...rator/39791322

If the flow seems to swell and then die, you've found your culprit....

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post #4 of 14 (permalink) Old 06-16-2017, 10:37 AM
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another less likely cause would be inadequate tank venting. may need to clean the vent in the cap and the vent lines

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post #5 of 14 (permalink) Old 06-16-2017, 01:47 PM
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Quote:
Originally Posted by Jumpingjerry View Post
I have a 2003 Vulcan with about 2800 miles on it. Been siting for years. Got it running good. Ear shave and coasters done. Ran with no problem for the past week, except the petcock had a small leak. Installed new petcock today. Now it seems to have an oscillating hesitation. Runs good, then boggs for a second, then runs good, and boggs, then runs good, and boggs......

No more leaking though. The petcock is new OEM.
"Got it running WELL."
"Runs WELL, then boggs for a second, then runs WELL, and boggs, then runs WELLER, and boggs......


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post #6 of 14 (permalink) Old 06-16-2017, 01:48 PM
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post #7 of 14 (permalink) Old 06-16-2017, 10:47 PM Thread Starter
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Quote:
Originally Posted by Knifemaker View Post
Yes sounds like it's not flowing fuel properly. You can check this by running two fuel lines from the petcock into a jar, and then applying some suction to the vacuum line.
You can use your mouth or one of these:
https://www.walmart.com/ip/Bulb-Syri...rator/39791322

If the flow seems to swell and then die, you've found your culprit....
Thanks! I'll give that a try.


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Originally Posted by michiganteddybear View Post
another less likely cause would be inadequate tank venting. may need to clean the vent in the cap and the vent lines
I did clean it last week, but I'll check it again.
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post #8 of 14 (permalink) Old 06-17-2017, 03:31 PM
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Did you replace the fuel hoses? I cut mine a touch too long and after a while it kinked enough to cut off one cylinder.

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post #9 of 14 (permalink) Old 06-18-2017, 10:53 AM Thread Starter
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Did you replace the fuel hoses? I cut mine a touch too long and after a while it kinked enough to cut off one cylinder.
They are new hoses. I've checked to make sure they are linked.
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post #10 of 14 (permalink) Old 06-18-2017, 11:11 AM Thread Starter
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So out of curiosity I took the old petcock apart. Found out that there was no spring in it. So the old one was working like a gravity petcock and worked great (except for the minor leak). Figured I would make the new one gravity fed petcock too. That seemed to fix my problem. The bike is running good now! I took out the plunger in the new petcock and soldered the vacuum nipple shut. I did use a manometer on the carbs and they both seems to have same vacuum on them.
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