Cleaned tank and now white smoke, hard to start and keep running - Page 2 - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Engine / Exhaust / Cooling
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post #11 of 17 (permalink) Old 09-26-2019, 04:33 PM Thread Starter
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If you changed the float valve (needle valve), give it and it's seat a close look.

Shake the float to make sure there's no gas in it.
I took the carbs out and replaced with all original parts. I cleaned everything out again (nothing appeared to be clogged) and made sure everything was reseated properly. I was able to get it to sit steady, but I'm back to my original issue - holding revs and issues riding.

Once I was able to just have it idle normally, I took it for a spin and found that when switching gears it would stick to the rev it was at (shifting from first to 2nd at 4k and then leaving clutch in resulted in it sitting at 4k for about 3 seconds then slowly returning back to normal idle.

I took a video of it when it was parked. The white smoked appears to have somewhat gone away. Not quite sure what the issue could be at this point.

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post #12 of 17 (permalink) Old 09-26-2019, 06:59 PM
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My idle is all over the place, when I first start the bike (without choke) it’s about 900rpm, when I drop it into first it dips a little more, but once the bike warms up it’ll stay around 1100 (where it should be). But I do notice that when I’m in the city and rev it hard from block to block I’ll get a delay for the idle to return all the way down. Meaning I’ll let off the throttle, it’ll drop from 3k to about 1300 but hang there, then slowly go back to 1100. If the bike did it last year when I got it I’d never think about it, but it didn’t. So I’m hoping you figure it out so I can get an idea.
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post #13 of 17 (permalink) Old 09-26-2019, 10:50 PM Thread Starter
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My idle is all over the place, when I first start the bike (without choke) itís about 900rpm, when I drop it into first it dips a little more, but once the bike warms up itíll stay around 1100 (where it should be). But I do notice that when Iím in the city and rev it hard from block to block Iíll get a delay for the idle to return all the way down. Meaning Iíll let off the throttle, itíll drop from 3k to about 1300 but hang there, then slowly go back to 1100. If the bike did it last year when I got it Iíd never think about it, but it didnít. So Iím hoping you figure it out so I can get an idea.
I grabbed a fresh tank of gas and dumped a bunch of seafoam in. I ran it for about 30 minutes on idle then stopped it, and I'm soaking it in seafoam overnight. I'll report back tomorrow.
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post #14 of 17 (permalink) Old 09-27-2019, 12:57 PM
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Ok, I got confused by the two "m" usernames. ???

Hanging idle is usually a sign of an air leak, often around the boots.

These carbs are really sensitive to temperature change, as far as idle speed goes. Sometimes on rides, when the temp dropped in the evening, I'd come to a stop and have to adjust the idle speed. Engine should be fully warm when you set the idle.

My bike has always had a small amount of 'hanging idle', re-seating the carbs has never made a difference, but I don't consider it bad enough to worry about.

Hang can also be caused by the air screw adjustment, so that's worth a try. Just set them for the highest idle with the least amount of turns outward/looser ... to the left.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #15 of 17 (permalink) Old 09-27-2019, 01:01 PM Thread Starter
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Ok, I got confused by the two "m" usernames. ???

Hanging idle is usually a sign of an air leak, often around the boots.

These carbs are really sensitive to temperature change, as far as idle speed goes. Sometimes on rides, when the temp dropped in the evening, I'd come to a stop and have to adjust the idle speed. Engine should be fully warm when you set the idle.

My bike has always had a small amount of 'hanging idle', re-seating the carbs has never made a difference, but I don't consider it bad enough to worry about.

Hang can also be caused by the air screw adjustment, so that's worth a try. Just set them for the highest idle with the least amount of turns outward/looser ... to the left.
So I sprayed some WD-40 around the boots to see if the idle would go up or change at all, and I didn't see any change after spraying all around. I checked vacuums as well and they all appear good. The strange thing for me is that I cannot notice any difference when adjusting the idle screw. I can have the screw literally all the way in, or backed out 5 turns with no difference (that I can tell). Any surefire way to know how to adjust these?
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post #16 of 17 (permalink) Old 09-27-2019, 02:08 PM
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So I sprayed some WD-40 around the boots to see if the idle would go up or change at all, and I didn't see any change after spraying all around. I checked vacuums as well and they all appear good. The strange thing for me is that I cannot notice any difference when adjusting the idle screw. I can have the screw literally all the way in, or backed out 5 turns with no difference (that I can tell). Any surefire way to know how to adjust these?
On any carb, lack of response from a mixture screw is a sign of a problem somewhere. Can be a clogged internal passage, air leak, or a rich/lean condition caused by anything other than that mixture screw.

In some cases it can be that the idle setting is beyond the range that the mixture screws control. On carbs with an idle transfer slot, if the throttle plate is open past the transfer slot, the mixture screw will be useless.
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2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 09-27-2019 at 02:11 PM.
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post #17 of 17 (permalink) Old 09-27-2019, 07:27 PM
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One thing I overlooked ... With the CV type carb, there's the possibility for the slide/diaphragm to hang, which would also hold the rpm up. If the slide hangs on decel, it will feed more fuel through the slide needle.

edit: These carbs can also leak air through the covers on the coast enrichers.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 09-27-2019 at 07:30 PM.
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