Fast Idle with warm engine - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 15 (permalink) Old 06-05-2012, 07:41 PM Thread Starter
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Fast Idle with warm engine

Wasn't sure what section this should go under.... Anyway, my 750 runs great, starts right up. When it's cold, I back off the choke, and it idles perfect at 1100.

What has been happening intermittently, is once I ride for a while, and the bike is good and warm, when I come to a stop sign, or stop for any other reason, the idle speeds up real high, up to about 4K RPM. If I slowly release the clutch, the RPM's go back down to 1100, but if I pull the clutch in again, they race right back up again to about 4K.

Is this the choke malfunctioning? This seems to happen on and off. One day it's Idling perfect once it's warmed up, the next it's idling real high again. I just got back from a ride and it was doing it real bad. I'd pull up to a stop sign and the thing is revving up at almost 5K RPM. I have to sit there and keep releasing the clutch to get it to calm down, slowly creeping into traffic...

Anyone know what the problem is?



Pete Herrmann
1994 Vulcan 750 40K on the clock and counting....

Bought 4/2011 28k Miles,
New Rick's Motorsports R/R
Tim Parrot Stator
Tuxedo Mod
KAW Saddlebag/signal relocation brackets
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post #2 of 15 (permalink) Old 06-05-2012, 07:51 PM
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You can visually inspect the choke plungers to see if they are closing properly. That would be a good start at least.

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
TOC MCCTs
Metzeler ME880 [110/90-19, 170/80-15]
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Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R


1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

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post #3 of 15 (permalink) Old 06-06-2012, 05:38 AM
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Maybe it's just a sticky throttle cable? Slowing down when you let off the clutch make sense because you're adding load to the engine, at the expense of your clutch plates! So when it's acting up will it pull you down the road at a good clip while "idling"?

4/12/12 1st bike ever! 95 VN 750 13k
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post #4 of 15 (permalink) Old 06-06-2012, 06:39 AM Thread Starter
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Quote:
Originally Posted by skyboxer View Post
Maybe it's just a sticky throttle cable? Slowing down when you let off the clutch make sense because you're adding load to the engine, at the expense of your clutch plates! So when it's acting up will it pull you down the road at a good clip while "idling"?
I don't think it's the throttle cable because if I'm slowing down for say, a traffic light, and down shifting, the engine slows normally. It's once I get down to 1st gear and the bike comes to a stop. The engine will then race up to about 4K RPM, and stay there until I attempt to put it in gear.

It seems to be doing the same thing the engine does when you first start it up and chock it. I've got to look at it today and see if the chock plungers are closing.

Am I able to see them easily from the sides of the bike??



Pete Herrmann
1994 Vulcan 750 40K on the clock and counting....

Bought 4/2011 28k Miles,
New Rick's Motorsports R/R
Tim Parrot Stator
Tuxedo Mod
KAW Saddlebag/signal relocation brackets
NGK Iridium Plugs
TOC MCCT's
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post #5 of 15 (permalink) Old 06-06-2012, 08:37 AM
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Surely if the choke were sticking the bike would choke up and cut out when hot, sounds like some sort of air leak somewhere diaphrams/intake boots or something.
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post #6 of 15 (permalink) Old 06-06-2012, 09:42 AM
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2 things:

Idle setting should be done when engine is warm....I know mine is very touchy and had similar results. maybe it just isn't properly set.....it's a longshot, but possible. Maybe you need to set the idle lower and use more choke until it warms up???

the other thing is....are you currently running seafoam in the fuel? if not, you might want to. The idle circuit might be gummed up or sticking, so seafoam can't hurt. just a note: When I run seafoam in mine, I usually get similar results until the next tank of gas....but that might be because of the amount I put in...maybe too much.
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post #7 of 15 (permalink) Old 06-06-2012, 10:44 AM Thread Starter
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Well I rode in to work today, and it was acting normal. I have just used Seafoam once, about 1000K miles ago. I'll put some more in and see if it helps.

The idle setting is fine as far as I can tell. This morning when I stopped at the lights, it went right down to 1100 just like it's supposed to do...



Pete Herrmann
1994 Vulcan 750 40K on the clock and counting....

Bought 4/2011 28k Miles,
New Rick's Motorsports R/R
Tim Parrot Stator
Tuxedo Mod
KAW Saddlebag/signal relocation brackets
NGK Iridium Plugs
TOC MCCT's
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post #8 of 15 (permalink) Old 07-02-2012, 06:41 PM
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same thing happening with my 05 Vulcan as well...

Pete, my 05 is having the same problem. It started happening after a minor service. Before the service it used to run fine, but now it starts up fine but the idling goes to 4K as soon as the bike is warm enough. Also, the idling is high even when I pull the clutch to change gears. I am guessing that the mechanic must have screwed something up (may be literally) in the carb. Any luck with a resolution?

2005 VN750
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post #9 of 15 (permalink) Old 07-02-2012, 07:51 PM
..have a vulcan good day!
 
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I may be way off base here, but if it were my problem I would be checking both carb boots for proper seal. JMO
WilliamTech

'86 VN750 13,700 mi -Stock
-Purchased 2008 w/8800mi
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...have a vulcan good day!
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post #10 of 15 (permalink) Old 07-03-2012, 09:33 AM
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carbs out of balance could cause some funny idle issues as well...
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