Vapor Lock - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
 
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post #1 of 1 (permalink) Old 01-19-2006, 09:50 PM Thread Starter
Vulcan Verses
 
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Vapor Lock

Also see Starting and Stalling
Also See Hot Starting Problem

Quote:
Q: I have recently had a unique stalling problem with my bike. I ride it about three miles to work. It sits all day. I come out, start it up, let it warm up, take off. Get about half a mile, it begins to sputter, then dies. I pull over. When I attempt to start it, it sounds like it wants to turn over, but doesn't. I don't crank it so as not to run down the battery. It seems all I have to do is let it sit for three minutes, then try to start it, at which time it will hesitate or kinda be sluggish just a moment when I first begin hit the start button, and then fire up.

This has never happened anywhere else - running to the store, going to the gym, or even on the way to work. As Pick can testify from our recent three-state ride, I never had a problem thru all the starting and stopping we did.

Could not letting it warm up enough cause this? What up? I'm knew I'd jinxed my bike when I recently referred to it as Unbreakable, and now I'm gonna have to come up with some reverse-osmosis voodoo sorta jinx removal ritual - to begin with, at 2:00 p.m. central time, everyone face Illinois and start ringing their ride bells.

BTW, FWIW, both time this happened, it was on really hot days with the bike sitting all day, sunbathing.

SN
A: When my first regulator (not stator) failed, this was a symptom. I never had this happen after the regulator was replaced... Might be unrelated but my stalling was always happening when the bike was HOT and I was in traffic. Almost felt like a fuel delivery problem. But it went away after the regulator was replaced...

A: Sounds like vapor lock Stewart. With the hot days we have had pressure can build up in the tank. A full tank sitting out in the sun will even leave a little puddle under your bike thanks to that vent tube. Next time you ride in, try just opening your gas tank and closing it to relieve the pressure before you start it up. Those of us down in the Suthern states have to contend with this every so often *S* One additional thing..you might want to check that vent tube too and just run a wire through it to make sure the tip isn't clogged with a bug or road crud. You Yankees just never had to deal with hot that much!

A: Make sure you have your tank vent checked. It sounds like your tank vent is not working causing a pressure build up. This condition is not vapor lock. Freak

A: I spoke with my trusty tech at Action Kawasaki, Bradenton, FL last week on this very issue. The problem, he says, is the size of the friggin float bowls in the VN750. Because of an obvious lack of space, they are tiny. Therefore, after the bike is hot and is shut down with no air flowing that hot air just cooks the gas out of the float bowls. Now, you turn the gas back on (I usually shut mine off if I'm gonna be away from the bike for any longer length of time) and they refill, but if they're still hot, it takes a few moments for the bowls to cool from the gas coming in and kinda stablize. Makes a lot of sense, actually. I agree with the information provided below on the tank heating due to the sun beating down on it. I installed a water tank with ice water and a sprinkler type device that showers the tank with cold water automatically from time to time while the bike is parked. HA Gotcha! NOT! Just kidding! TB
Quote:
If your bike falls over, even gently while not moving and the engine dies..it's not a good idea to try and start it right away. I learned this durring my dirt bike years... First anytime the bike falls, you should take the time to check every part out for damage..this includes cable play, lever action and the wiring around the steering head. If you can, while doing this, open the throttle and tie it open with a bungee cord or something. When the bike falls, gas in the float bowl sometimes will spill into the intake throat,,sometimes backing up to the airbox..this gas will in effect flood the engine. Letting it set with the throttle slide open helps it to evaporate. It should be noted then that if the float bowl empties, there may not be enough gas in them to start the bike. Also it's possible that an air bubble has entered the fuel line if the bike was on it's side (more common if fall to the right) Oil also gets sloshed out of the crankcase, give it time to settle back. (some dealers have reported a high number of upper end problems with some sport bikes. one of the causes was found to be the riders constant practise of doing long extended wheelies..the oil level in the bike was being tilted back and not getting picked up by the pump..so the bikes were in essence not getting oil) Also remember that dropping your bike may cause stress, and even a few "pumps" of adreniline being introduced in your body. This is not a good condition to ride a bike under. A rider should not be stressed or "emotionaly" effected when opperating the motorcycle. Give yourself and the bike a small break...then after completing your checks, and getting back into the right frame of mind..try starting the bike. KM
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Re: running on one cylinder (sometimes) Two things come to mind...actually, three.

1. The vent hose fromt the tee over the carbs to the back of the right ear (air filter housing) may be bottoming out. Pull it back slightly; better yet, cut it off at a 45 angle, so it can't shut off the vent.

2. The tank vent under the cap may be closing off, or the tank vent tube is stopping up. The vent in the cap itself is very tiny, and it doesn't take much. BTW, that tiny vent benefits from being drilled out with the next size up wire guage bit. Take the cap apart before you drill it, tho! ;-)

3. The most likely one--trash in the carb needle seats. Take the drain plug out of the bottom of each carb and let the fuel drain out, then use the little red spray tube with a can of Gumout to load the float bowl with it, holding a finger over the drain plug hole, and spraying up thru the drain hole. Flood the float bowl with the Gumout, then remove the spray tube and your finger. Couple of times with each carb oughta do it. It's easier to tell when the bowl is flooded if you pull the vent hose out of the right ear and let it dangle out the side; Gumout will come out the tube when it's full. Replace the drain plug, leaving it slightly open, put the vent tube back in the right ear, put the tank back on, turn the petcock to Off 'til fuel starts coming out the drain, and close the drain plugs. Turn the petcock on, fire up the bike, and see how she runs then. hth Jim
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