Won't maintain idle or rpms. - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 24 (permalink) Old 09-29-2011, 05:11 PM Thread Starter
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Question Won't maintain idle or rpms.

I just bought a 2001 Vulcan 750 and rode it home. After a couple of days I went to ride it and it started at a very high rpm. I adjusted the idler and it ran at idle for about 10-15 minutes then shut off. Now it won't maintain enough rpms to stay on unless I stay on the throttle.
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post #2 of 24 (permalink) Old 09-29-2011, 05:26 PM
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Maybe cable throttle problems. Try turing the front wheel back and forth see if anything changes while the engine is running something may have been forceing the throttle cable to open up the carbs more. If you backed off of the idle rod adjustor, that may be why she will not idle now and having to keep the throttle advanced.


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post #3 of 24 (permalink) Old 09-29-2011, 05:27 PM
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Welcome to the forum!

It's possible that something in the carb was sticky (float/needle valve maybe) that was giving the engine some extra fuel. That would jump your RPMs, sort of like running it with choke. After it had run a while, it's possible that the problem cleared itself, meaning that you now need to turn your idle adjuster back up until you keep it steady around 1100 RPM.

These machines like to be run. I've found that if mine sits a while, it sometimes has hick-ups like what you described. Usually, just running it (and regular Seafoam in the tank) will take care of the problem.

It is also possible that, in the process of running it, one of the pilot (idle) jets got some crud in it. This would require some throttle to keep it running.

In either case, it wouldn't hurt to pull the drain screws and hose a bunch of spray carb cleaner up into the bowls and let it drain back out. Put the screws back in and give it a try.

I've (knock on wood) only had to pull the carbs on my Vulcan once, so we'll have to let one of the carb gurus on here give more specifics (and tell me where I went wrong).

Best of luck,
Hippie
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post #4 of 24 (permalink) Old 09-29-2011, 05:49 PM Thread Starter
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Quote:
Originally Posted by hot_rod_hippie View Post
Welcome to the forum!

It's possible that something in the carb was sticky (float/needle valve maybe) that was giving the engine some extra fuel. That would jump your RPMs, sort of like running it with choke. After it had run a while, it's possible that the problem cleared itself, meaning that you now need to turn your idle adjuster back up until you keep it steady around 1100 RPM.

These machines like to be run. I've found that if mine sits a while, it sometimes has hick-ups like what you described. Usually, just running it (and regular Seafoam in the tank) will take care of the problem.

It is also possible that, in the process of running it, one of the pilot (idle) jets got some crud in it. This would require some throttle to keep it running.

In either case, it wouldn't hurt to pull the drain screws and hose a bunch of spray carb cleaner up into the bowls and let it drain back out. Put the screws back in and give it a try.

I've (knock on wood) only had to pull the carbs on my Vulcan once, so we'll have to let one of the carb gurus on here give more specifics (and tell me where I went wrong).

Best of luck,
Hippie
Thanks, I have tried turning the idler back to no avail. And I read about the pilot jets, but am unsure how to go about them. I am unfamiliar with carbureted engines. Is this something I will be able to see with out much dis assembly?
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post #5 of 24 (permalink) Old 09-30-2011, 10:40 AM
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First post in this thread points to a download of the Kaw manual for our bikes:
https://www.vn750.com/forum/showthread.php?t=17667

It'll help you get familiar with some of the internal parts of the carb. For the no-removal carb cleaner flush I mentioned, pg 30 of the .pdf (2-13 according to the manual) has a diagram showing the location of the drain plug. There will be the same thing mirrored on the other side. Remember to put something under the carb to catch any gas/solvent that runs out (volatile liquids + potentially hot surfaces = bad).

If that doesn't solve the problem and carb removal is needed, directions are included in the manual (though some members may have a better method). Do a search on the forum about carb cleaning for lots of good tips/specifics.

Good luck,
Hippie
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post #6 of 24 (permalink) Old 09-30-2011, 01:17 PM
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I would have to suggest some Seafoam, or in my case, I like Lucas Oil's "tuneup in a bottle" - basically, some good injector/jet cleaner. I would suggest putting some in the tank, start it up, let it run for just a few to get it circulated through, then let it sit overnight maybe.

There are also some instructions in here somewhere about adding something directly to the carbs and letting them sit overnight. You might try that if the above-mentioned doesn't work.

I agree that these things like to be run, and mine also gets "tempermental" - sputters, coughs, etc - if I let it sit for more than 3 or 4 days without running. They are also notably sensitive as far as fuel and carbs go, and I find that mine does best if I run cleaner in it about every 3 or 4 tankfulls.

If that doesn't work, nor do the other suggestions, you might be looking at something a little more involved - other issues with carbs or maybe petcock. There's lots of info in here though, so if you keep at it, with the help of the "gurus" here, you should be able to get it figured out. Whether or not you can fix it yourself or have to take it into a shop - well, that's all based on your mechanical ability, time, etc. I had to have the carbs pulled on mine, and I took it to a good shop here in town - just didn't have the time or space (live in a condo with no garage - what the hell was I thinking?!?) Lol

Good luck = )

AZ Kev

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Turned 11,000 mi Nov 2011
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Otherwise, all stock


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post #7 of 24 (permalink) Old 09-30-2011, 02:10 PM
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Quote:
Originally Posted by AZ Kev View Post
(live in a condo with no garage - what the hell was I thinking?!?) Lol

Good luck = )

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post #8 of 24 (permalink) Old 09-30-2011, 06:29 PM
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↑ ↑ ↑ Lol!

Arizona Kev

1989 VN750
7800 orig mi when purchased Jan 2011
Turned 11,000 mi Nov 2011
Saddlebags
Taillight relocation kit
Chad's highway peg mounts
Emgo Pegs
Aftermarket mirrors
Dunlop D404's

Otherwise, all stock


"But it's a dry heat - like the inside of an oven"
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post #9 of 24 (permalink) Old 09-30-2011, 10:41 PM
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Get it running, even if you have to stay on the throttle. Maintain the lowest possible constant engine speed for about ten seconds, then shut it off while maintaining throttle. Pull a plug from each cylinder and look at the electrodes (center hooks). If they are white, you are starving for fuel, if they are black, you are running rich.

That's a good place to start. Let us know what applying the choke does too.

I wouldn't try taking jets out on the bike since you have never seen the insides of the carbs.

There's really only one hard part to pulling the carbs: everything. But, after the third or fourth time you will be able to do it in around a half hour. It's rough the first few times, but the satisfaction of making it run is worth the effort.

When I hook the carbs back up for a trial run, I don't bother reattaching the cables right away. The choke and throttle can be manipulated by hand just to see if you can get it running again.

If you end up having to pull them, I can give you some of the tricks I've learned.

If it ain't broke... well I'm sure I can find something that is
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post #10 of 24 (permalink) Old 10-01-2011, 06:24 PM Thread Starter
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Thanks a lot guys. I got it running. What I did was I just kept starting it and playing with the idle knob. I think I found the spot seeing as it starts and runs reliably.

Now my issue is that is runs stays at about 3000 rpms when I squeeze the clutch lever to down shift and stays at a high idle. I have tried adjusting it down but can't seem to find a spot that doesn't drop it below 1,000. Is this normal for my bike?

And thanks Hippie I will download or purchase a manual when I get access to a computer. I do most of my internet through my smart phone.
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