Runs great till shut off and restart - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
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post #1 of 11 (permalink) Old 03-13-2011, 04:28 PM Thread Starter
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Runs great till shut off and restart

Hi guys,

New here but love the site. You guys are all very knowledgable for sure so I am hoping you can help me with this one.

I have a 1990 VN 750 and I seem to have a strange problem I havent found on the forums.

I have rebuilt the carbs and the bike runs great.

Until I shut it off for a few minutes and restart it.

At that point it will idle but tries to die out with any throttle. I can crack the throttle and get it past it, but only by working the throttle.And it wont clear up. I have to almost limp it home at lower RPMs.

Now if I wait long enough it will be ok..
And also, I have noticed that midrange throttle at times has a slight miss to it also. But not all the time.

Do I need to re-do the carbs again? ugg..

Roach

FT Myers, Fl
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post #2 of 11 (permalink) Old 03-13-2011, 04:43 PM
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you might have dislodge some gunk in the tank when you rebuilt the carbs, or your vent hose to the right ear is bottoming out, or you might have the pre POOGS (phantom out of gas syndrome) starting. Start by mixing some sea foam into the gas, cleaning the fuel tank vent (search POOGS), and check the hose to the right ear for blockage or bottoming out. if that doesn't work, try using a syringe filled with gas to shoot back up through the carb drain holes. only as a last resort pull the carbs... try the above mentioned things first and post back... I am almost positive we can fix it with out a carb pull.
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post #3 of 11 (permalink) Old 03-13-2011, 06:04 PM Thread Starter
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I have seafoam. I will give that a try.. But I am confused on the right ear? Is that one of the vent lines that come off of the carbs? And I will search POOGS and see what comes up.
Thank you very much for your quick response, I will post back this evening after I give it a ride.
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post #4 of 11 (permalink) Old 03-13-2011, 06:49 PM
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good post on the hose I am talking about...

Slight Skipping @ 60mph
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post #5 of 11 (permalink) Old 03-13-2011, 09:31 PM Thread Starter
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Yeah, I got it. I put seafoam in the tank.. Cleared the vent lines at the cap and the tank.. I will be riding to work tomm, so I can post after that and let you know how all goes.
Thank again for the great info.

Roach
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post #6 of 11 (permalink) Old 03-14-2011, 06:59 AM
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post #7 of 11 (permalink) Old 03-14-2011, 07:41 PM Thread Starter
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Well good news bad news.. I got done with the vent cleaning, and the bike was running great.. At the end of my ride I jumped on it a little and after I hit second gear, the bike started running very badly. Now if I play with the choke it runs ok, but still no power after about 1/4 throttle..
Did I send some more crap into my carbs?
So you know. After I cleaned the vents, I drove for about an hour, shut the bike off, and it started the second I hit the starter.
The bad news happened on my way home after. And its doing that now too.. I just got home and starts right up, but bogs down at 1/4 throttle or more..

Thanks guys
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post #8 of 11 (permalink) Old 03-17-2011, 12:22 PM
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Have you checked your plugs? If i got this right you started with a problem from 1/8th to 1/4 throttle and ended with a 1/4 and up? If you plugs are working properly then you have blockages in your carb. From 1/8 to a 1/4 throttle you have transfer ports. These are VERY tiny holes in the inside of the carb. If you start at the bottom of the carb and go to the bottom of the throttle butterfly, you will find a tiny hole. That is the Idle port. If you crack open the trottle just a little you will un cover 3(i think) tiny holes that become exposed progressively. These holes are responsible for providing fuel and idle to 1/4 throttle. They connect to the float bowl and all of them run off of the Pilot Jet. This is the most common area to have problems as they are the smallest passages. This must be done with the carbs out. I have never done it, but I heard that if you drain you float bowls and fill them with seafoam, then leave it overnight. It will get rid of a lot of that. Its a lot easier than pullin the carbs.
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post #9 of 11 (permalink) Old 03-17-2011, 01:30 PM
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Definitely sounds like some crud lodged in the carbs being inconsistent like it is. I think I'd start with the seafoam filling the bowls and let it sit overnight, then drain the bowls and see what happens.

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post #10 of 11 (permalink) Old 03-17-2011, 01:53 PM
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Be sure to check or replaced the vaccuum hose from the petcock to the carb intake. This hose is the on and off switch to the fuel. If it is crack it can suck air and keep the fuel from flowing.

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