5th gear stutter? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 05-30-2014, 11:46 PM Thread Starter
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5th gear stutter?

I feel that this topic may have been covered many times before but I tried searching and didn't come with anything relevant, I apologize if I missed something.

I've heard this is called the Vulcan Stutter? Is there a fix? About 50 Mph in 5th gear when you give it a decent amount of throttle, it fall's on it's face and sputters and kick's like an infant.

The bike is a 1988 VN750 with full Cobra Exhaust, haven't checked the see if the air filter is stock, previous owner said it was jetted which I don't believe needs to be done just with the pipes? Maybe I'm wrong.

Is this a common problem? Any fixes anyone know's? It seems like it's getting too much fuel to me, any idea's?

Also, I drained the tank and filled it with 91 Octane, it seem's "Better?" but not fixed.

Much appreciated!

Last edited by Cruiser; 05-30-2014 at 11:56 PM.
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post #2 of 7 (permalink) Old 05-31-2014, 12:35 AM
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I've not heard of them stuttering unless something is wrong with the bike, These CV carbs require that the vent tube (usually tucked behind the right ear) not be plugged and end in "dead air" Also while every VN seems to be a little different about this running the bike with the filters or ear covers removed produces a huge stutter at higher rpms. On my bike before the earshave just running without the ear covers made the engine stutter terribly above 4000 rpm to the point where it wouldn't accelerate much past 4500 rpm.

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post #3 of 7 (permalink) Old 06-08-2014, 09:29 PM
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there is a thread on it here. mine did the exact same thing at same speed. there is a tube from between the carbs that should route to the right ear, if it is not in the ear or missing its getting to much air. cut the tip of it at a 45 degree angle before inserting it into the ear. search the forums and you will find the thread.

1986 vn 750 aka "Huck Farley"
42,000 miles
Rick's stator and rr
Tuxedo stator cover mod
pickup coil mod
dampers replaced
agm m/f battery
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splines lubed
custom "vn750.com" grill cover
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acct to mcct mod https://www.vn750.com/forum/showthread.php?t=17917

rekeying locks, https://www.vn750.com/forum/showthread.php?t=7309

stator replacement walkthrough, https://www.vn750.com/forum/showthread.php?t=11369
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post #4 of 7 (permalink) Old 06-08-2014, 09:50 PM
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this isnt the original thread but explains it a little.
https://www.vn750.com/forum/showthread.php?t=54857

1986 vn 750 aka "Huck Farley"
42,000 miles
Rick's stator and rr
Tuxedo stator cover mod
pickup coil mod
dampers replaced
agm m/f battery
Harley sportster exhaust, degoated
Hid conversion
splines lubed
custom "vn750.com" grill cover
NGK Iridium spark plugs


acct to mcct mod https://www.vn750.com/forum/showthread.php?t=17917

rekeying locks, https://www.vn750.com/forum/showthread.php?t=7309

stator replacement walkthrough, https://www.vn750.com/forum/showthread.php?t=11369
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post #5 of 7 (permalink) Old 06-09-2014, 02:10 PM
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Quote:
Originally Posted by Cruiser View Post
I feel that this topic may have been covered many times before but I tried searching and didn't come with anything relevant, I apologize if I missed something.

I've heard this is called the Vulcan Stutter? Is there a fix? About 50 Mph in 5th gear when you give it a decent amount of throttle, it fall's on it's face and sputters and kick's like an infant.

The bike is a 1988 VN750 with full Cobra Exhaust, haven't checked the see if the air filter is stock, previous owner said it was jetted which I don't believe needs to be done just with the pipes? Maybe I'm wrong.

Is this a common problem? Any fixes anyone know's? It seems like it's getting too much fuel to me, any idea's?

Also, I drained the tank and filled it with 91 Octane, it seem's "Better?" but not fixed.

Much appreciated!
I have never heard the term "vulcan stutter"
I agree with Wib and Fool...you most likely have an exposed carb bowl vent. The 2 vent lines from the carb are "T"'d together and run behind the right air box or "ear" into a slotted hole on the back of the box....it needs to be vented, but not in the wind.

ALSO: these bikes were designed to run on regular gas...no real need to use high octane, but it is up to you.

I would also suggest running SeaFoam in your tank for a few tankfulls...it does wonders to clean out varnish in the carbs and prvent future issues in the fuel system.
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post #6 of 7 (permalink) Old 06-22-2014, 08:49 AM
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Quote:
Originally Posted by wib714 View Post
there is a thread on it here. mine did the exact same thing at same speed. there is a tube from between the carbs that should route to the right ear, if it is not in the ear or missing its getting to much air. cut the tip of it at a 45 degree angle before inserting it into the ear. search the forums and you will find the thread.
Will this caise the bike to run lean as well?
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post #7 of 7 (permalink) Old 06-22-2014, 11:15 AM
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By not having the carb bowl vent hose terminating in "still air", it can cause the fuel levels to do strange things and the bike will stuble and surge at speeds.

The vent line after the "T" should de in a location that allows venting, but not be subjected to wind or forced airflow while at speeds. The normal location is behind the right air filter housing. The hose is cut on a diagonal so it won't bottom out when inserted in the hole on back of the filter housing that has a slit down the length of the hole. Another option is under the tank attached to the plastic nipple under the fuel level sending unit cover, this allows air to vent without being in turbulence.

Air flow into the end of the hose will cause air pressure in the carb bowls, air flow across the end of the hose will cause a vacuum in the carb bowls.....both will effect fuel flow and cause running issues at speeds.

I hope this explains it better for you.
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