Newbie versus the fuel petcock - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 16 (permalink) Old 05-30-2009, 11:41 AM Thread Starter
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Newbie versus the fuel petcock

Okay, so this morning I had plans to meet up and have breakfast with a buddy of mine that I used to work with before we got laid off a few months ago. Figuring that he hadn't seen my new bike yet and I didn't get to ride to work all week due to rain, I decided to take my baby out this morning.

First time on the interstate (I still want a shield, but 65-70 wasn't as bad as I thought it would be) and she felt great as she really stretched her legs for the first time with me. My fuel guage read about at the halfway mark so I figured I was good. The trip was only about 10 miles on the interstate.

About halfway there, I noticed a "flat spot" in the throttle. Going right about 60-65, 4k on the tach and I twisted the throttle and nothing happened. She still was keeping speed, but it just wouldn't go any faster. Then, suddenly, the throttle would kick in and I would take off, which was quite surprising. I get to the exit and as I pull up to the light, she dies. I didn't know what else to do, so I flipped the fuel petcock to reserve and made it to my destination with no other issues. Thinking this was causing the problem, I rode all the way back home with it on reserve and no "flat spots" in the throttle. I could twist and she would immediately respond. I did noticed that on the way back, I dropped pretty fast from 1/2 on the fuel gauge down to about the 1/4 mark. Pull into the gas station and turn the petcock to off. I fill up with about 2 gallons and I continue down the road. She sputtered and died right as I was coming up to a parking lot right off the street. I cruised in with no power and got off. I then realized that I didn't turn the petcock back on, so I put it to the on position and fired her up and road home with no issues.

After that long winded description, obviously I goofed like a newb by not having the fuel "on" after leaving the gas station. But do you all think my "flat spot" on the throttle was the fuel getting below where the normal pickup is in the gastank? Should I just take it that the halfway mark on the gauge is closer to a third of a tank left and fill up then? She seemed to take forever to go from above full down to the halfway mark, but only took 10 miles on the interstate to go from a half down to a 1/4.

2004 Kawasaki Vulcan 750 "Serenity"
Changed Oil/Filter and Coolant
Installed Big Crank ETX15L Battery w/charger hookups
Duct-taped retention safety for toolbox door
New OEM clutch lever replaced after first tipover
Plan on: changing brake fluid, coastering, lubing splines, relocating R/R, new saddlebags, highway pegs, windshield.
Scratch that...make that getting her ready for sale. Nope, scratch THAT! I'm keeping her!
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post #2 of 16 (permalink) Old 05-30-2009, 12:31 PM
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Adding only 2 gallons should've been a little short of reserve. It's possible the petcock screen is plugged up.
Get some Seafoam and add a few onces to 1/2 a can. See what that does to help things.

It's common for the fuel gauge to take awhile to go from full to 1/2, and to rapidly go from 1/2 down. But, IMO, only 10 miles to go from 1/2 to 1/4 seems a little too rapid


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post #3 of 16 (permalink) Old 05-30-2009, 07:07 PM
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It takes about 100 miles for my gauge to get to mid-way, but it dives like a Stukka past that point. I did learn fairly early on, however, when I first noticed this behavior and wrote the left-leaning fuel indicator to an "alarmist" fuel gauge, that when it hits that reserve line, it *means* it...

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post #4 of 16 (permalink) Old 05-30-2009, 07:38 PM
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You could have a couple of things going on - reserve being one, but the flat spot is about where you'd expect it if your carb vent tube is moving around on you. S/B in the right air filter housing unit, but the tube has a tendency to pop out, face forward, mess up the air flow in the carbs, then face backwards and be ok, etc. So I'd check that, too, just to make sure that's not adding to your fuel issue (and Hyper may be right about the petcock screen, so that's probably worth taking a look at as well, especially if the Seafoam doesn't do the trick).

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post #5 of 16 (permalink) Old 06-05-2009, 07:12 AM Thread Starter
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After a week's worth of rain, I finally was able to get her back out on the road to ride to work this morning.

Actions taken:
I filled up on the way home Saturday, so I had a full tank to start out with. Yesterday, I removed the right air filter housing to check the vent tube. Seemed to be in there good, but I read here somewhere else about it bottoming out and getting totally closed off and that causing an issue. So I just cut a little 45 angle in it so that if it does ever bottom out, there's still some air that gets through that tube. I always use Seafoam in the gas (always meaning both times I've gotten gas).

Results:
Everything went fine on the ride this morning. No rough engine, no stalling at traffic lights, and full responsive throttle all the way (I was only able to get up to 60, but I feel this is close enough for my test run).

I'm convinced that I just let the tank get down past the upper fuel pickup and because I didn't turn it to reserve, starved it of fuel. I reset my odometer so I can track exactly how much mileage I'm getting out of my tank before I have to go to reserve. I didn't pay attention before because I figured the fuel guage would take care of me! So I'm still learning alot.

I probably wasn't too precise about the the location of the needle on the guage, but I'll try to keep a hawk's eye on it this time so I know exactly when to expect to turn it to reserve.

Thanks for the input guys!

2004 Kawasaki Vulcan 750 "Serenity"
Changed Oil/Filter and Coolant
Installed Big Crank ETX15L Battery w/charger hookups
Duct-taped retention safety for toolbox door
New OEM clutch lever replaced after first tipover
Plan on: changing brake fluid, coastering, lubing splines, relocating R/R, new saddlebags, highway pegs, windshield.
Scratch that...make that getting her ready for sale. Nope, scratch THAT! I'm keeping her!
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post #6 of 16 (permalink) Old 07-15-2009, 09:49 AM Thread Starter
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Update:

Ever since my last problem and fill up, I've had a close eye on the fuel guage and the trip odometer. Again, it took forever to go from past full down to a half or so. But I was relying on the trip for this test. On the way home from work yesterday, just as I got near my turn for my street, I started feeling that jerky, loss of power feeling. Starving of fuel I think. It died on me as I rolled onto my street. Turned the petcock to "reserve" and after about 50 yards or so, she finally started up (I was rolling silent the entire time) and made it to the house with no issues.

Trip odometer reads 76, so if I assume that 1/3 of the tank runs on reserve and I've gone 76 miles on the first 2/3's, I can still go another 38 miles before she runs out completely. I don't think I'm going to test this, I'll get gas next time I ride to work. I mostly do short commutes that involve 3 traffic lights so I'm sure I'm not getting as good of mileage as I would be going at a consistant speed down a country road.

2004 Kawasaki Vulcan 750 "Serenity"
Changed Oil/Filter and Coolant
Installed Big Crank ETX15L Battery w/charger hookups
Duct-taped retention safety for toolbox door
New OEM clutch lever replaced after first tipover
Plan on: changing brake fluid, coastering, lubing splines, relocating R/R, new saddlebags, highway pegs, windshield.
Scratch that...make that getting her ready for sale. Nope, scratch THAT! I'm keeping her!
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post #7 of 16 (permalink) Old 07-16-2009, 02:44 AM
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Quote:
Originally Posted by 04newbie View Post
Update:

Ever since my last problem and fill up, I've had a close eye on the fuel guage and the trip odometer. Again, it took forever to go from past full down to a half or so. But I was relying on the trip for this test. On the way home from work yesterday, just as I got near my turn for my street, I started feeling that jerky, loss of power feeling. Starving of fuel I think. It died on me as I rolled onto my street. Turned the petcock to "reserve" and after about 50 yards or so, she finally started up (I was rolling silent the entire time) and made it to the house with no issues.

Trip odometer reads 76, so if I assume that 1/3 of the tank runs on reserve and I've gone 76 miles on the first 2/3's, I can still go another 38 miles before she runs out completely. I don't think I'm going to test this, I'll get gas next time I ride to work. I mostly do short commutes that involve 3 traffic lights so I'm sure I'm not getting as good of mileage as I would be going at a consistant speed down a country road.
3.6 gallon capicity with 1 gallon reserve. So you are getting 29.3miles per 1.3 gallons. Do you fill up on the center stand or side stand? Do you ride above 65 mph? You should not need reserve untill you get close to "E", you may be experiencing the "out of gas syndrome" that happens when you get low on fuel. Usuall it is caused by a fuel vent problem.

If it happens again, open the gas cap close it then start the bike.

Providing your gauge is accurate, I recently replaced my fuel sending unit and now i don't run out at half tank. In my case I have K&N filters on the carbs which means I had to shim the rear tank mount for clearence and that gives me less reserve.

When I hit reserve my gauge is on "E" Which is fine because I know I have a little over half a gallon left. At this point it takes 2.8 gallons on the center stand to fill up.


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Last edited by lance328; 07-16-2009 at 02:56 AM.
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post #8 of 16 (permalink) Old 07-16-2009, 03:38 PM Thread Starter
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Quote:
Originally Posted by lance328 View Post
3.6 gallon capicity with 1 gallon reserve. So you are getting 29.3miles per 1.3 gallons. Do you fill up on the center stand or side stand? Do you ride above 65 mph? You should not need reserve untill you get close to "E", you may be experiencing the "out of gas syndrome" that happens when you get low on fuel. Usuall it is caused by a fuel vent problem.

I fill up on the side stand, are you saying I can get more gas in at a fillup if I put her up on the centerstand? And no 65 mph. The fastest I get is 55 on the last leg near work. Most of the rest is 25-45. And I was wrong, my trip od. was at 85 when I climbed on her today, not 76. Does this "phantom out of gas syndrome" occur where the petcock is "on" or "res"? Because once I flipped it to reserve, no issues whatsoever and I never opened the gascap.

If it happens again, open the gas cap close it then start the bike.

Providing your gauge is accurate, I recently replaced my fuel sending unit and now i don't run out at half tank. In my case I have K&N filters on the carbs which means I had to shim the rear tank mount for clearence and that gives me less reserve.

When I hit reserve my gauge is on "E" Which is fine because I know I have a little over half a gallon left. At this point it takes 2.8 gallons on the center stand to fill up.
I think my guage is right at the 1/4 mark right now and I'm running in reserve just to be safe until I hit the gas station after work. My goal here isn't to figure out my mpg, but to know when I need to fill up before I start sputtering.

Weird side question. If I knew exactly when I had to fill up, and always did, and never had to flip it to reserve, would that gas that sitting in the lower part of the tank theoretically never get used? or does it slosh around enough to keep it all mixed up between old and new?

2004 Kawasaki Vulcan 750 "Serenity"
Changed Oil/Filter and Coolant
Installed Big Crank ETX15L Battery w/charger hookups
Duct-taped retention safety for toolbox door
New OEM clutch lever replaced after first tipover
Plan on: changing brake fluid, coastering, lubing splines, relocating R/R, new saddlebags, highway pegs, windshield.
Scratch that...make that getting her ready for sale. Nope, scratch THAT! I'm keeping her!
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post #9 of 16 (permalink) Old 07-16-2009, 03:59 PM
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My bet is, it sloshes enough...

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post #10 of 16 (permalink) Old 07-16-2009, 04:42 PM
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My bet is, it sloshes enough...
I think so too. IIRC from high school chemistry class, there is something called "The theory of maximum randomness", (or something close to this) that explains the mixing of liquids of equal weight or gases.

If there is any water in the tank, it should be at the bottom, because it is more dense the gasoline. However, since you have been running on reserve sometimes, as well as using Seafoam, I don`t think water is the problem.

Any dirt, rust or other heavy crud will naturally migrate to the lowest point in the tank as you ride. Since that is where the fuel pick-up tubes are located, Hypers surmise that the petcock screen could be plugged makes sense to me.

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