throttle bog and coughing - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 3 (permalink) Old 07-05-2012, 11:57 PM Thread Starter
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throttle bog and coughing

Okay, I am a bit of a newb but this site has been my resource. I have been able to find answers to almost any issue I have had with my vulcan here. I bought a 94 a few months ago and it has ran great until recently. It seemed that all of a sudden I had top end sputtering when I gave it a lot of throttle that didn't happen before. After reading as much as I have on here, I decided that it was probably a clogged main jet so I pulled the carbs for a cleaning and rebuild. Thanks to roach's helpful videos, I felt confident enough to do it myself. I thought that while I had them off, I may as well do the earshave and rejetting as well. I followed phil's earshave directions for that. everything went okay (except for a broken bolt at the reed valve which I knew to watch out for, but I still managed to break it off.) I was able to get coastered, shaved, and rejetted, but when I reassembled today, I still have the same top end issue. I plan on syncing the carbs tomorrow, but it still starts and runs well with little throttle. Now the bog down still happens, but there is a coughing and a little smoke at the exhaust manifold when it give too much throttle. I am going to double check all the hoses, boots, etc for an air leak, but I don't think I have one. Could this be an electrical problem? It seemed to start on a really hot day. I'll also check all my connections. Or is this fuel starvation? the petcock? It doesn't die when i give it throttle, but almost. And now I am noticing this coughing with some smoke. but maybe the smoke isn't new but i am just noticing it now because I don't have those giant ears blocking the way. I checked the oil, and it seems fine, but I changed it anyways. Any insight would be greatly appreciated. I am not opposed to taking the carbs back off and re inspecting the floats and whatnot, but i know it cant be the jets since there are new ones in, right? I thought the carb was the issue, and maybe it still is, but I cleaned it thoroughly... again, insight, please! p.s. it is a little rusty around the exhaust, and I think that is where the smoke is coming from, but it only seems to really come when it coughs from me cranking the throttle..
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post #2 of 3 (permalink) Old 07-06-2012, 08:39 AM
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I would first check that the fuel enricher plungers are closing. Then I would check the spark plugs for good spark to both cylinders. If those check out ok I would think you have a float or needle valve problem.


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2001 Vulcan 750
TOC upgrade on ACCT
Air/fuel mixture set to 2 1/2 out
rectifier relocated
splines lubed
decals removed
upgraded mirrors
Pic up coil mod done
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post #3 of 3 (permalink) Old 07-06-2012, 11:34 AM
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Might also consider dumping some Seafoam in too. My bike would hesitate at 2K RPM then rapidly climb with a little more throttle. She would sputter and one of the cyclinders would simply quit firing. I added half a can of Seafoam to a full tank; and, HOLY ****, she idles smooth, is real smooth thru all RPM ranges, and has a little more pep than before. I highly recommend this.

Good luck!

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carbs , coughing , exhaust , fuel starvation

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