Bike is slow to drop to idle - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 24 (permalink) Old 05-17-2010, 12:03 AM Thread Starter
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Bike is slow to drop to idle

I've been noticing lately that my Vulcan revs down very slowly once the engine is thoroughly warmed up. I was having a problem with the bike not idling well but that seemed to go away after I gave it a heavy dose of Seafoam. The only thing I did (or tried to do) was adjust the throttle cables. Did I adjust the throttle cables wrong or is something else going on?

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post #2 of 24 (permalink) Old 05-17-2010, 12:18 AM
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If it started after you adjusted them I would suspect that first also,The service manual gives a procedure for adjustment,but basically you need to leave a very slight bit of slack in the accelerator cable and the decelerator cable should have no slack.
your throttle should have a little free movement before it starts to move the throttle open,2 to 3mm according to the book.




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post #3 of 24 (permalink) Old 05-17-2010, 12:32 AM Thread Starter
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I tried to go by the book, but when I tried to twist the adjuster on the throttle, it wasn't rotating, but twisting the entire throttle cable. How do I avoid that? And yes, I did loosen the lock-nuts.

Would my poor adjustment explain the rough idling I experienced too?

1994 Kawasaki Vulcan 750 named Jinba Ittai (Japanese for "Horse and rider in perfect harmony").
Jardine Pipes
Splines Lubricated
Painted Instrument Bezels
Headlight Visor
Chrome engine guard
Leather Fork Bag (contents: Pressure gauge, tools, and a Book of Psalms)
Yuaso MF AGM Motocross battery
Kenda Kruz Front tire
Duro Boulevard rear tire

"Buy the ticket, take the ride."
-Hunter S. Thompson
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post #4 of 24 (permalink) Old 05-17-2010, 12:42 AM
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Quote:
Originally Posted by VulcRider24 View Post
I tried to go by the book, but when I tried to twist the adjuster on the throttle, it wasn't rotating, but twisting the entire throttle cable. How do I avoid that? And yes, I did loosen the lock-nuts.

Would my poor adjustment explain the rough idling I experienced too?
only if your idle is set too low to begin with did you try to adjust it with the black knob on the left side of the bike .It should be idling around 1000 to 1100 rpm. There is more adjustment at the carb end of the cables besides what is at the throttle but it is a pain to get your mitts in there.If you can get your idle steady,then adjust the throttle cables,Are your fuel screw plugs still in or can you see the screws
?




If you see it on my bike I did it
VROC#30324
92 vn750(sold)
Current ride 05 1500 Classic FI
lovin' the new scoot



Quote:
"When all is said and done,usually more is said than done" UNK
Click on one x and drag to the other to read between them.

Psalm 40:1...
XI waited patiently for the Lord; and he turned unto me, and heard my cry. X
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post #5 of 24 (permalink) Old 05-17-2010, 01:11 AM Thread Starter
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Yes I have been adjusting the idle to 1050 like the book suggests. And I'm not exactly sure what you mean by fuel screw plugs. I'll have to check that tomorrow.

1994 Kawasaki Vulcan 750 named Jinba Ittai (Japanese for "Horse and rider in perfect harmony").
Jardine Pipes
Splines Lubricated
Painted Instrument Bezels
Headlight Visor
Chrome engine guard
Leather Fork Bag (contents: Pressure gauge, tools, and a Book of Psalms)
Yuaso MF AGM Motocross battery
Kenda Kruz Front tire
Duro Boulevard rear tire

"Buy the ticket, take the ride."
-Hunter S. Thompson
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post #6 of 24 (permalink) Old 05-17-2010, 01:15 AM
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Quote:
Originally Posted by VulcRider24 View Post
Yes I have been adjusting the idle to 1050 like the book suggests. And I'm not exactly sure what you mean by fuel screw plugs. I'll have to check that tomorrow.
That book of Psalms in your tool bag is good to see!




If you see it on my bike I did it
VROC#30324
92 vn750(sold)
Current ride 05 1500 Classic FI
lovin' the new scoot



Quote:
"When all is said and done,usually more is said than done" UNK
Click on one x and drag to the other to read between them.

Psalm 40:1...
XI waited patiently for the Lord; and he turned unto me, and heard my cry. X
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post #7 of 24 (permalink) Old 05-17-2010, 09:16 AM
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While you are looking, test and make sure your throttle is snapping back to the return all the way. If it is, every time, then it sounds like a vacuum leak that opens up when the engine is warmed up. Have you had the carbs off?

It stands to reason that your cables are not adjusted right, but strange things happen sometimes where a non related item will show up and make you think you did something to cause it. I'm just throwing it out there!

Fergy
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post #8 of 24 (permalink) Old 05-17-2010, 09:45 AM
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Check the throttle, both cables, and the linkage on the carburetors. Sometimes things get dried out or corroded. When you open the throttle all the way with the engine off, it should instantly snap closed when you release it. If it doesn't, it is binding or sticking somewhere. The "fuel screw plugs" refers to the lead plugs over the idle air/fuel mixture screws. there is one on each carb. If they are still there, leave them alone for now. The factory setting isn't perfect, but will not cause the kind of problems you are describing. If they are missing, go ahead and remove both screws and springs, spray a little Gumout carb cleaner into where the screws were, then spray WD-40 on the screws, put them back in, turn them until they seat lightly, then back them out about 2 1/2 turns. That is a good starting point. It should run fine there. If both the throttle/cables/linkage and the A/F mixture screws are ok, then start looking for vacuum leaks between the carbs and the engine, or in the carbs themselves. Both carbs have a vacuum fitting on them. Make sure they are not leaking. Don't worry about looking for air leaks between the air filters and carbs right now. While leaks there can let dirt into the engine over time, they will not lean out the air/fuel mixture enough to cause problems. Check that after you get the engine running right. Jerry.

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post #9 of 24 (permalink) Old 05-17-2010, 04:25 PM
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If all else fails, check the diaphrams in the carbs. They may have gotten stretched out or even ripped.

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post #10 of 24 (permalink) Old 05-17-2010, 11:00 PM Thread Starter
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Ok now that this talk of vacuum problems has come up I suppose it is important to mention that my carbs have been leaking a little fuel. The leak was much more pronounced when I first pulled my bike out of winter storage earlier in the spring, but the leak seems to have gone away since the weather has warmed up. The leak appears to be coming from the gasket between the carburetor body and the cylinder head on the rear cylinder.

Went for a 100+ mile ride today and the bike performed very well, this ride included a hot run through some wonderful twisties in the beautiful Pennsylvania countryside. When I say hot run I mean hard accelerations and higher revs (Never exceeding 7,500 RPM mind you). Everything seemed normal and all the power seemed to be there when it should be. Another thing the bike will do very rarely is miss under acceleration. When it does miss, it will usually only missfire once or twice and then act like normal. I'm assuming that air is getting somewhere it shouldn't?

I frequently check my throttle as part of my pre-ride inspection and have always heard and audible snap coming from the carbs which I'm assuming means the throttle is hitting its stop.

Thank you for all of your help. Do you think a carb overhaul is in order?

1994 Kawasaki Vulcan 750 named Jinba Ittai (Japanese for "Horse and rider in perfect harmony").
Jardine Pipes
Splines Lubricated
Painted Instrument Bezels
Headlight Visor
Chrome engine guard
Leather Fork Bag (contents: Pressure gauge, tools, and a Book of Psalms)
Yuaso MF AGM Motocross battery
Kenda Kruz Front tire
Duro Boulevard rear tire

"Buy the ticket, take the ride."
-Hunter S. Thompson
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