Hesitation and rough running at 4k-5k - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 3 (permalink) Old 11-09-2010, 03:58 PM Thread Starter
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Hesitation and rough running at 4k-5k

Newbie here to the forum and as a Vulcan owner. I just purchased a 1997 Vulcan 750 with 22,000 miles. I recently replaced the exhaust with Vance and Hines Cruzers. I also replaced the stock air filters with K & N filters. I replaced the main jet in the carb to a 135 and a 138. Same problem with both jets. As soon as I hit 5th gear and try to cruise about 55-60 @ 4k RPM's the bike runs rough and sounds like it is missing. I checked the carb vent house that is supposed to be in the intake ear and cut it at 45 degree angle and tried relocating it- still have a problem. Is the main jet still to small? Please help. I really like this bike and I am starting to wish I never started modifiying it. Thanks.

1997 Vulcan 750
V & H Cruzers
K & N Filters in stock ears
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post #2 of 3 (permalink) Old 11-09-2010, 05:49 PM
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Welcome to the Vulcan madness.

Is it possible you have over-oiled the new K&N filters?
Maybe as the rpms climb, the engine runs leaner.

PM lance328 with your mods and the elevation at your location. He will be able to tell you what jets you should be running, and any other advice on the 750.


1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

H-D windshield
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July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15

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post #3 of 3 (permalink) Old 11-09-2010, 08:51 PM
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I think the problem is the vent hose you cut and relocated. It has to be protected from the wind or you get exactly the symptoms you describe. Cutting it does no good if the wind can get to it. Cutting at an angle is to keep it from bottoming out in the stock air filter housing.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
"Black Beauty"
1989 VN750 acquired December, 2008, 6,711 miles
Currently 23,298 miles

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2001 Honda CMX250 Rebel acquired July, 2008

1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts
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