Gas Troubleshooting - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
 
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post #1 of 1 (permalink) Old 01-17-2006, 09:09 PM Thread Starter
 
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Gas Troubleshooting

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Q: Today on my way home the big quit again on me (actually 3 times in 5 miles).

It appears that it is starving out for guess when tank is low( or is itflooding ). This happened once before on meSo when I got to nearest gas station I filled up and it ran fine the rest of the way home just like last time .

I put 2.7 gallons in it so it was close to empty .What I have done to date:

1. run two tanks of gas with seafoam through it

2. when it quit I vented with gas cap open in case of vacuum problem

3. pulled plugs and checked them they are fine

It stalls out at around 3500 - 4000 rpm and feels like it is starving for gas. It will turn over but not start. I vent gas tank, wait a few minutes and start it with full choke and it finally starts, off choke rpm dropped to 700 or so . I turned rpm up a little , road a mile and quite again same symptoms, waited got it started and finally got to gas station, filled up and it was fine .

I think it holds 3.0 and 3.6 with reserve and all I could get in it was 2.7.
I flipped to reserve and made no difference in starting. I was trying to get it down to make sure reserve was working, I don't think I ran out of gas but don't know what could cause to stop like this. It certainly isn't the carbs it ran fine once I put gas in it. If I was not on reserve then pick up hose was not plugged either . Interestingly choking must force enough gas to get another mile and it starves out again SO any thoughts, suggestions and help would be appreciated
To double check that vapor lock is the cause, you will need to have an extra key and do this while driving (be careful). When the condition is close to happening or just occurred, unlock the gas cap (which will open it up a bit) and eliminate or confirm this cause. Check ALL of your fuel and vent lines. If you have a slight kink, the pressure of a full tank might overpower the slight kink. Along the same line, I have read on the group there is some vent hose that gets jammed in too tight on the air box and causes problems. Have you ever actually removed the petcock from the tank? Crud can settle at the bottom of the tank. Most petcocks have a screen over them and reserve & regular inputs are inside the screen. The curd (or a partially blocked screen) would make the reserve useless. Do you have an inline fuel filter? If so, it could be slightly plugged so it needs the extra pressure of a full tank. Loran (Naperville IL)

1) One of the different things that I had done before starting it the last time was really tip the bike back and forth hard to slosh the gas around a lot. I don't know if this is what got me running or not, but you might try it next time to see if it helps.

2) It wasn't a vapor lock, I opened my gas cap several times and it didn't have any affect.

3) In my case, it might have been a transient crude in my fuel line.

4) Of the many hoses people have suggested checking, have you checked the hose coming off the back of the tank to make sure it is clear and undamaged.

Check the vac tube from the petcock and clean the **** out of that whole pathway. Let us know. If BD changed tanks and petcock, that might not have addressed the vacuum issue from the source. My 2.

Quote:
OK..this has happened to me and I have a few general theories what is happening here. Because it only seems to happen when you are low on gas..just around that point you are going to the reserve tube..This would mean that the main line is getting some gas...and..some air..So it's my theory that the fuel lines are getting air bubbles trapped in them and That is what is effecting the petcocks vacuum and the supply to the carbs. The petcocks reqire a back pressure from the cabs to let fuel flow..that is if the area behind the diaphram is fuel.if there is air there..the other fuel in the line falling to the carb is creating a slight vacuum where the air bubble exsists..nulling the effect of the vacuum line..and hence stopping the flow of fuel. The carbs bowls empty..and thus you seem to be out of gas. Sloshing the tank back and forth may simply be knocking the air bubbles back up and eliminating the problem. If the carbs get low, it will take several attempts to get it started while the engine needs to turn awhile to get the carbs to suck on the vacuum line and get the fuel to flow and fill the bowls up. Other bikes that I have had that had the simple gravity feed petcocks never had this problem..so the only way I could test this theory would be to install one on the bike. I do not believe it is crap in the tank clogging the resserve. Happens on brand new bikes and even ones that get the SEA Foam treatments...I doubt it is a kink in the line..becuase you'd then have fuel flow problems all the time...However there may be some corralation between the volume of air in the tank and the effect it has on the petcocks vacuum. Knifemaker
Push the petcock lever: Down for normal running. Forward for reserve. Backward to shut off fuel flow.

Others here have recommended running the bike on reserve now and then. I run mine on reserve for a few miles every tankful.

Anyhow, on my petcock (as it's known) there are three positions - ON, PRI, and RES. ON (pointing straight down) is where it's mostly left. When I get running real low I swing the lever so it's pointing towards the front of the bike - that's RES. I remember is as "Swing lever forward to keep going forward." PRI is for prime. For prime to make sense, I'll explain how this petcock works. On my petcock there isn't an OFF position. That's because the petcock is off' when the engine is off. This petcock uses the engine vacuum to open-up and allow fuel to flow when it's in the ON or RES positions. Now if you've drained your carbs, it's going to be real tough to use engine vacuum to open-up the petcock to let fuel into the carbs - that's what PRI is for. It will allow the fuel to flow even if the engine isn't running. I just keep mine in the ON position. But with gas prices going up, I have been flipping to RES more often. Best Regards, Chris
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