idle acting wierd - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 05-14-2013, 12:08 AM Thread Starter
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Exclamation idle acting wierd

Ok I seen someone else kinda touched on this but i didn't see aend result.
So my wife has a 2000 vn750. It does not like to idle very well.
Ok the facts:
I start the bike, full choke and warm it up, then it seems to idle fine around 1k for a bit the then it starts to have a wandering idle. once she starts riding it starts to die at stopsigns and lights.

I have had to turn the star screw i think almost all the way CCW. i change it to 3k and back it just a touch and it drops back down to around 1500.

Then when she tries to take off and shift gears it wants to idle around 3k sometimes. i tried to readjust it and it craps out again

I can't seem to find a sweet spot on the star screw. I pulled the plugs and they looked good to me. I also found the rubber boot (i think air intake on the rear carb.) off i put it back on.

It still does the same wierd crap.
She loves the bike it use to be her dad's but shes scared to ride it cause it won't stay running or it over revs.

Any information you could provide would be great.
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post #2 of 7 (permalink) Old 05-14-2013, 11:15 AM
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check your idle adjustment knob....sometimes the cable causes it to "wander" since it rotates and may try to go back up after setting it.

Balance your carbs....mine were off a bit and I had similar issues.

Choke adjustment....make sure the plunger is moving freely and has full stop when off.

Lastly...check for air leaks in the choke plunger and on the carb boots.

The last thing to ponder is fuel flow...maybe the petcock is restricted and the carbs are not filling properly???
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post #3 of 7 (permalink) Old 05-14-2013, 11:20 AM
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poor idling is along with over reving is a sign of a vacuum leak. Check the the vacuum hoses as well as the intake manifold boots. I bet the carbs aren't sealed right or the boots are dry rotted slightly. Another possibility is the slide diaphragm isn't sealing inside the carbs, or its hanging up. either way I would pull the carbs to look for obvious signs of dry rot or cracked vacuum lines, if nothing found remove the 4 screws holding the diaphragm and check it out to make sure its not buggered up.
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post #4 of 7 (permalink) Old 05-17-2013, 07:52 PM Thread Starter
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cool im off this weekend ill try looking at those things.
Ill post results.
Oh one other thing it did sit outside for a good bit of its life so dry rot might be an issue.
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post #5 of 7 (permalink) Old 05-18-2013, 04:16 PM
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Mine just developed the same issue.


Also the "Phantom Out of Gas" Issue popped up yesterday.

I'm going to look at some things tomorrow.

I'm Really interested in learning what you determine the problem to be.
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post #6 of 7 (permalink) Old 05-18-2013, 06:55 PM Thread Starter
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so i found the two little lines the ones marked red and blue cracked. I don't know if that will cause this but there cheap il get new hose.

The big find, so i didnt have carb cleaner but i had either.
I lightly sprayed around the carbs. the rear didnt really change but the front did.
Ther was an increase in RPM when i sprayed near the cyl. boot. the rear of the front carb no change.

Ok now to the guys that have ripped ther carbs off... how tight should the boots be?
now ill look for a loose air inlet above the carb or a loose clamp from carb to cyl. they look in really good shape and still plyable no visable weather check.
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post #7 of 7 (permalink) Old 05-18-2013, 08:21 PM
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The clamps should just be good and tight, but don't go until you can't turn the screw any more. Don't want to strip the threads or screw heads. On a single carb, I check to see if the carb moves in the boot when tweaked slightly, if it doesn't move, it's tight enough. Hard to do that with both carbs being bolted together like they are.

Generally, if you can't move the clamp, it should be tight enough. Use one hand and and stop when the screwdriver starts to slip.

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