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 Motorcycle Safety
 Technical/Maintenance
 Engine sputters out at 1/4 throttle.
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Bean
Male Senior Member
260 Posts


Pinellas, FL
USA

Kawasaki

94' Vulcan 750
Peer Review:

Posted - 04/20/2005 :  11:43 AM                       Like
I bought a Vulcan750 not long ago. It's a 94 with 10K miles and my first bike. I've been riding it without problems for about a week.
Tuesday I went for a short ride and it was fine till I stopped at a red light and attempted to go again. It kept stalling out and I eventually had to push it off the road.

Long story short. It's got a new battery, new plugs, new gas and idles perfect. If I leave it sitting in neutral and give it 1/4th (maybe even less) throttle, it stalls.

If I leave the throttle at idle, and adjust the choke, I can get all the RPM's I want. In fact this is how I got home Tuesday. Perhaps that's a hint as to where the problem is.

I've gotten several opinions, but I'd like to hear what you guys have to say before mentioning them though.

-Kevin

Edited by - Bean on 04/20/2005 12:08 PM

Bunky
Junior Member
71 Posts


Balto., MD.
USA

Honda

94 Shadow 600 VLX

Posted - 04/20/2005 :  12:34 PM
I'd try the easy things first, fuel filter, fuel screen in tank. I had the same problem and it was just the filter. Check the tank for rust. Good luck!!
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subvetSSN606
Senior Member
418 Posts
[Mentor]


Ellettsville, IN
USA

Suzuki

800 Intruder

Posted - 04/20/2005 :  2:00 PM
I concur with "easy stuff first" (Translate: cheap ;) )

Also check for a vacuum leak. But that's more likely if you've recently worked on the bike.

And the really simple one... Got gas?
I'm not kidding, NO insult intended, it's happened to many, myself included. But that's exactly the symptoms you'll get if you're running out of gas, or try to run with your fuel valve closed.

Tom
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Bean
Male Senior Member
260 Posts


Pinellas, FL
USA

Kawasaki

94' Vulcan 750

Posted - 04/20/2005 :  9:43 PM
Tank is full. Although I admit I once forgot the petcock when I first got the bike it's not the case here.
My bike doesn't appear to have a fuel filter. Maybe I'm crazy?
I looked for a vacuum leak with no luck. I just used some smoke to see if it'd suck in anywhere. I also sprayed some canned starter spray on and around the carbs with no effect. Those tests may not be very through. I'm still new to this stuff. I figure as quick as it's stalling out, if it was a leak it must be pretty bad.

-Kevin
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subvetSSN606
Senior Member
418 Posts
[Mentor]


Ellettsville, IN
USA

Suzuki

800 Intruder

Posted - 04/21/2005 :  12:36 PM
Don't know for sure, but it's likely the fuel filter on that bike is integral to the tank/petcock.

It's very possible you have a clog in the carbs and they need cleaned, but that's not a trivial job. Not terribly hard, but can be an intimidating pain in the butt. So I still go with eliminating the easy stuff first.

Two other easy ones to check...

Air filter (sounds more like you're starved for gas, but starved for gas or air will give similar symptoms, so it's possible and it's easy to check.)

Tank vent- If the vent gets clogged, as you use gas you start to draw a vacuum on the tank and the gas won't flow to the carbs. (It's similar to putting your finger on the top of a straw, if you can't get air in, nothing comes out) Try running the bike with the gas cap off (in the driveway, don't ride it that way), if the problem goes away, it's the vent. Don't know if the vent on yours is in the gas cap or a separate tube that may have gotten clogged.

Good luck,
Tom

PS Did you ever notice a hissing noise when opening the gas cap? If so... go for the vent.

Edited by - subvetSSN606 on 04/21/2005 12:41 PM
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Nighthawk
New Member
17 Posts


USA

Posted - 04/21/2005 :  12:39 PM
quote:
Originally posted by Bunky

I'd try the easy things first, fuel filter, fuel screen in tank. I had the same problem and it was just the filter. Check the tank for rust. Good luck!!



How do you check for rust?
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Bean
Male Senior Member
260 Posts


Pinellas, FL
USA

Kawasaki

94' Vulcan 750

Posted - 04/21/2005 :  1:44 PM
I was hoping it would be a fuel filter issue. It turns out my bike doesn't have one. Looking at the parts diagrams it doesn't appear to be part of the petcock either. I'm thinking of buying an aftermarket one though once this is all said and done. They're so cheap I can't see why they're not standard. Perhaps there's a performance penalty or something.

I had already tried the venting route. All is well there. Looks like I'll be cleaning the carbs this weekend. The bike's 10 years old so even if that's not the problem it probably needs a good cleaning anyway.

I'm still open to any suggestions.

-Kevin
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Bean
Male Senior Member
260 Posts


Pinellas, FL
USA

Kawasaki

94' Vulcan 750

Posted - 04/25/2005 :  12:00 PM
Fixed the bike! Turned out to be the carbs. I cleaned them out throughly and the bike now runs fine. I didn't see anything horrific in there but I assume one or more of the jets were clogged.
As for the fuel filter. My petcock has screens in the tank. From what I understand these don't get the fine particles, just bigger stuff (pieces of rust for example). So I plan on adding an aftermarket inline fuel filter.

-Kevin
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Bean
Male Senior Member
260 Posts


Pinellas, FL
USA

Kawasaki

94' Vulcan 750

Posted - 04/26/2005 :  12:12 PM
*sigh* Well after two days of riding it's at it again. Luckly I was nearly home this time. I was riding along at about 35mph. Then revs started dropping. It nearly stalled when I used some choke to keep the engine running. At this time I was in the center lane to make a left into my neighborhood. Once there was a break in traffic I gave it some gas and it stalled. Started up again but unlike before it was sputtering even while idle. I held enough throttle to keep it from stalling. Waiting for another break in traffic and once again stalled it trying to go.
I then gave up and pushed it off the road the next chance I had. With it still off I parked it on the side of the road and checked for anything odd. Then I started it again and it ran completely fine!? I got it home and let it cool down.
After about an hour I started it again. I was never able to get it to a running temp. It stalled without the choke. With the choke (even at 1/2) the revs were erratic. And as before, giving it throttle made it sputter and eventually stall.

I'm getting very frustrated as this is my only vehicle (asside from pub bus system). I spent my entire weekend cleaning the carbs. Had it running fine, now suddenly it's back to square one. My only guess is there's **** in the tank and it found it's way into my jet(s) again.

-Kevin
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subvetSSN606
Senior Member
418 Posts
[Mentor]


Ellettsville, IN
USA

Suzuki

800 Intruder

Posted - 04/27/2005 :  5:17 AM
I dunno!

Sounds like you have OBS... Old Bike Syndrome! Try as you might, it's still persnickety!

Lets drop back to the basics...
For an engine to run you need just a few things... fuel, air, spark, and compression. Sounds like you've been all over the fuel system, unless it's a petcock problem.

Let's look at air... If you pulled you're carbs it's not at all inconceivable that you have a problem with one of the boots. Those boots are notoriously difficult to get back on... and given that it's an old bike the rubber may be stiff and hard to get a good seal.

At this point I'm guessing, and really don't know. You could also pull your plugs and see if there's any indication of running lean or rich in general or in any particular cylinder.

Wish I had a "Ya! Do this" answer for you, but I don't.

Tom
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scottrnelson
Advanced Member
6950 Posts
[Mentor]


Meridian, ID
USA

Honda

XR650L, 790 Adv R

Posted - 04/27/2005 :  9:12 AM
If I were having this problem, I would remove the fuel tank and drain it completely. Get every last ounce of fuel out of there. Pay attention to what comes out. Is it clean all the way?

While it's off, you can verify that the petcock works correctly and that all of the hoses flow fuel properly. You've now eliminated one more variable from whatever is causing your problem.
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Bean
Male Senior Member
260 Posts


Pinellas, FL
USA

Kawasaki

94' Vulcan 750

Posted - 04/27/2005 :  12:28 PM
Well I think it's safe to say we've found the problem. Here's my gas:

Image

-Kevin

Edited by - Bean on 04/27/2005 3:04 PM
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scottrnelson
Advanced Member
6950 Posts
[Mentor]


Meridian, ID
USA

Honda

XR650L, 790 Adv R

Posted - 04/27/2005 :  3:01 PM
Now you need to figure out how to get the residue out of the tank.

I used steel wool on my 888 tank and a vacuum cleaner to get the dust and little bits of steel wool back out. Removing the gas cap assembly gave me enough room to get my whole hand inside. Then I rinsed with clean gas and ran the gas into a coffee filter in a big funnel and into a one gallon milk jug. About six rinse cycles was enough for it to be clear coming back out.

You can display the image directly like this:
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Bean
Male Senior Member
260 Posts


Pinellas, FL
USA

Kawasaki

94' Vulcan 750

Posted - 04/27/2005 :  3:05 PM
Ah, wasn't sure if this board allowed that. Thanks!

I'm glad to say all is well once again. Obviously that gas had to go. I was lucky there wasn't any rust. It was more like ooz (that dark bottom layer). I gave the tank repeated rinses with clean gas + treatment stuff (I forget the name). Had to burn the old gas already in the carbs but after that baby ran like new again. I took a 10 mile trip being sure to go up and down a few hills to be sure things are good. Has a bit more pep then before and my backfire while slowing down seems to be gone as well :)

Knowing what I know now, the first thing I would have done after buying that bike would have been draining the tank. I hope others can learn from this little story of mine :)
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Indiana Randy
Moderator
2118 Posts
[Mentor]


Fort Wayne, Indiana
USA

Honda

2000 Magna V4 750

Posted - 04/27/2005 :  3:54 PM
Ucko Mucko! That's the BEST (as my Doctor friend would say) example of bad gas I've ever seen!

Glad you found the problem.

Have you looked inside your tank with a flashlite to see if there's any rust in there? If so, you need to treat your tank with POR-15 or equivalent.

I'd definately put an inline fuel filter on it. They're cheap.

Wave when ya see me!
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