Idle Keeps Having to Be Adjusted - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 07-01-2009, 11:55 PM Thread Starter
 
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Arrow Idle Keeps Having to Be Adjusted

I was having trouble with the bike keeping a high RPM at high speeds after I pull the clutch and put it in neutral - the RPMs wouldn't go down until I slowed down. I was told to check the throttle cables.

I drove it home. Cables seem ok. Problem is still there - in fact NOW the RPMs stay at 4k at complete stop. I tried turning my idle down and that worked. WOW - BUT THEN the idle starts dying and I have to turn the idle BACK UP!!!!!

So, that leads me to think that it's idling at different intervals of power. Sometimes it wont idle - so I have the idle up - then it does the high RPMs thing again and I turn the idle down - I keep going back-and-forth.

I have a feeling you're going to be seeing me a lot on these boards...

Last edited by SyntaxJO; 07-02-2009 at 12:52 AM.
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post #2 of 9 (permalink) Old 07-02-2009, 12:05 AM
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hmmm, i had the SAME problem on my KZ. I adjusted my air-bleed screws. I believe turning them out richens the mixture. Also, your idle circuit could be clogged, and that would require a carb cleaning. Cleaning the carbs fixed allllll my problem and several are what youre having. I didnt have a reliable idle.

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post #3 of 9 (permalink) Old 07-02-2009, 12:32 AM Thread Starter
 
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I just cleaned the carb - it runs at full power now... The only things I'm not sure about are my air-bleed screws. I have no idea where they are set - I just screwed them in all the way then unscrewed each one a full turn (why did I decide a full turn... I don't know - please excuse my foolhardiness). I'll have to get those balanced - how to do that? I don't know but I'm sure I'll figure it out.
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post #4 of 9 (permalink) Old 07-02-2009, 12:36 AM
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Youre on the right track. My owners manual says the default is out one turn. Be sure to turn both the same to keep your carbs in sync. Next, try turning them both out two turns. See what thay does. maybe 3.

1986 Vn750
18,800 miles, and counting
Bone Stock
New cam chain tentioners
all fluids changed
Spline Lube
windshield
Engine Guard
B-stone S11 RWL-stock sizes
*wanted*
New grips

2001 Vn750
13,100 miles, and counting
spline lube
Bridgestone S11 100/90
Shinko 170/80
rear end oil change
aftermarket mirrors
windshield
otherwise all stock
*anticipated mods*
Engine Guard
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post #5 of 9 (permalink) Old 07-02-2009, 12:41 AM
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These being out of adjustment will cause a SLOW deceleration of the rpms. crack the throttle rapidly getting it to about 5,000 watch how long it takes for it to get back to idle. turning them out will increase the deceleration. and richen your idle. hope this helps.

1986 Vn750
18,800 miles, and counting
Bone Stock
New cam chain tentioners
all fluids changed
Spline Lube
windshield
Engine Guard
B-stone S11 RWL-stock sizes
*wanted*
New grips

2001 Vn750
13,100 miles, and counting
spline lube
Bridgestone S11 100/90
Shinko 170/80
rear end oil change
aftermarket mirrors
windshield
otherwise all stock
*anticipated mods*
Engine Guard
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post #6 of 9 (permalink) Old 07-02-2009, 12:51 AM Thread Starter
 
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You are fantastic - that is exactly what's happening - slow decel of RPMs - but that's when it's not sticking on a high RPM. Man I have a good feeling about this - I WILL report back.
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post #7 of 9 (permalink) Old 07-02-2009, 01:17 AM
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I had the same problems on my kz. And I just learned all this today. Even though I have a different carb than you, the same principals apply.
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post #8 of 9 (permalink) Old 07-02-2009, 03:26 AM
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Quote:
Originally Posted by SyntaxJO View Post
I just cleaned the carb - it runs at full power now... The only things I'm not sure about are my air-bleed screws. I have no idea where they are set - I just screwed them in all the way then unscrewed each one a full turn (why did I decide a full turn... I don't know - please excuse my foolhardiness). I'll have to get those balanced - how to do that? I don't know but I'm sure I'll figure it out.
Set pilot screws bwtween 2-2.5 turns from closed. Factory setting is 1 5/8 turns.


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post #9 of 9 (permalink) Old 07-02-2009, 10:48 AM
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Quote:
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Set pilot screws bwtween 2-2.5 turns from closed. Factory setting is 1 5/8 turns.
More realistically, factory setting is **supposed** to be 1 5/8. That doesn't guarantee any are set that way, and I've heard countless stories of what people are finding.

Here's a good shade tree mech trick to get the idle mixture "just right" without actually using a dyno.

With the bike warm and idling, start turning the mix screw in until the bike stumbles. Then back it out about 1/2 turn. Repeat with the second carb and voila. You are now set above the minimum for *your* bike to run/idle, keeping in mind that not only is every bike different, but there are also locality factors that impact the settings - tempertaure, altitude, etc.

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