Will not idle without choke - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 5 (permalink) Old 03-30-2014, 10:34 PM Thread Starter
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Will not idle without choke

1986 Vulcan 750. It has only 1200 miles on it from its first eight years of life, then it sat in its first owner's garage from 1994 until I bought it a couple of months back. I have not yet had much time to ride it but have been pecking away at a couple of issues.

There is only one obvious issue: it will not idle with the choke off. It starts and runs fine with the choke on and runs fine with the choke off--but it dies at idle without the choke. I raised the idle speed, but that make no difference.

As soon as I turn off the choke at idle, the engine dies. I tried turning the choke off very gradually, and it still dies instantly--not gradually, and without any spluttering--at a certain point. However, with just a bit of throttle, it will run fine without the choke. In fact, once warm, it will start just fine with or without choke, as long as I give it a bit of throttle.

So I have to be a bit careful riding with the choke off. I have been surprised a couple of times when a slight delay in re-engaging the clutch during a shift has resulted in the engine dying and restarting when I let the clutch out--accompanied, of course, by a screech and a strip of rubber on the road. But, alas, that is why I keep the throttle up just a bit, leave the choke on, or just make sure my shifts are very fast--and why I am here posting this question before I log too many more miles.

I know I probably have to dig into the carburetor to see what is going on, and I have not made that jump yet; however, it will help to go into that with some sense of what these symptoms really mean. I would think plugged jets would tend to have an effect across the throttle range and not simply prevent non-choke idle.

On the other hand, maybe the description below of another issue is related and will jog something loose in someone's mind: it seems gutless on hills. It is very happy doing 65 in fifth on the freeway, but when starting out in first gear uphill, it seem very powerless (choke or no choke). Even with full throttle, it will just lug down and die if I do not ride the clutch for what seems to me an extraordinary distance.

It seems fine on the level, if a bit sluggish on acceleration, but because this is my first bike beyond a Honda 200 dual-sport, I am not sure what I should expect. And any kind of uphill, even a gentle climb on the Interstate in fifth at 65, lugs the engine somewhat and requires a downshift to fourth.

I added Sea Foam to the first couple of tankfuls of gas to see if it would clean out the carburetor/jets, but it made no difference. And that is about as far as I have driven it (maybe 200 miles). I read a post (elsewhere) that said that the Vulcan choke is not truly a choke but a fuel bypass and that inability to run without choke would indicate plugged jets; however, that does not explain why it will run BUT NOT IDLE without choke.
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post #2 of 5 (permalink) Old 03-30-2014, 10:46 PM
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Air screw may help a bit. factory setting is 1 5/8 turns out, most of us run 2 1/2 turns out. more than 3 1/2 turns out and you risk the screw vibrating out while you ride but it sounds like your slow jets are fairly well plugged and need to be cleaned.
A few guys here have managed to pull the jets with the carbs in but I can't get the screwdriver in to do it.

If your slow jets (also called pilot jets) are that dirty it's probably time to just pull the carbs and do the deed.

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post #3 of 5 (permalink) Old 03-30-2014, 10:46 PM
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Yea your carbs are definitely gunked up. I imagine the float needles are basically sealed shut or open like mine were and you probably have tons of other stuff clogged. There is a good video on YouTube that gives you step by step directions to pull em apart and clean em. I used it and it worked great.

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post #4 of 5 (permalink) Old 03-30-2014, 11:16 PM
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Try fillin the carbs themselves with SeaFoam....thats done by removing the tank, and using a small funnel on each line...let that sit for 48 hrs....

....now...drain whats in there thru the bottom and do a backblow on each carb......(proceedure is outlined in a sticky in the Carb section)...

If THAT dont work...ya may need to yank the carbs....but just fer sheits and giggles....remove the air intake boot off the carbs...or even just yer air cleaners (assuming youre all stock)....see how it runs....report back tomorrow sometime....Im goin to bed....

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post #5 of 5 (permalink) Old 03-30-2014, 11:30 PM
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Try dropping your jet bowls and pushing some fuse wire"real Thin" up through the idle jet, there are two jets in there and a third brass stump to confuse you, remember the idle jet is beside the carb body wall closest, to you and the main jet.

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