Vapor Lock... Again?!

[Lawrence]

Had what can best be described based on symptoms as a vapor lock last weekend. Rode my 2000 V11 Sport about 20 miles on a warm afternoon, stopped 10 min for a cool drink and engine, after starting right up sputtered as if starved for fuel. After a tow home and about 2 hours of head scratching and forum searching, I got turned on to the vapor lock scenario. Went out to the garage, bike started right up! Rode it the next day for about another 20 miles with no problems.

 

Today, with air temp around 85F, I went for about a 5 mile ride to a weekly evening bike gathering, parked bike for about an hour and as I left, same symptoms as last weekend, but made it about 1/4 mile before the stall. Let it sit for 30 min, tried again and stalled on me again. I am now leaving it over night to see what will happen in the morning.

 

I just keep thinking that there may be something else. The fuel pump and fuel lines did not feel too warm when this was happening, although the cylinder was very hot.

 

Could the bike be over-heating? How can I verify that I am getting oil pressure? And passage through the oil radiator?

[luhbo]

You should listen to the pump. It tells you all what's going on. Listen to it how it sounds in the morning and listen how it sounds when it's running free in a vapour bubble. Everybody can tell the difference. It's that easy, really. Cycle the pump (or more precisely the ecu) switching the kill switch until you can hear the standard flush, then press the starter button.

 

Hubert

[Lawrence]

You should listen to the pump. It tells you all what's going on. Listen to it how it sounds in the morning and listen how it sounds when it's running free in a vapour bubble. Everybody can tell the difference. It's that easy, really. Cycle the pump (or more precisely the ecu) switching the kill switch until you can hear the standard flush, then press the starter button.

 

Hubert

 

Hubert, Thanks for the tip. I do know the sound of the pump priming when the ignition key is turned on, but need to pay attention to it when it is in a vapor bubble. However, I don't follow, the pump cycling... sorry, a little dense over here... With the ignition key on, cycle the kill switch until the correct flushing sound is heard and this will clear a vapor lock bubble?

[luhbo]

... With the ignition key on, cycle the kill switch until the correct flushing sound is heard and this will clear a vapor lock bubble?

 

This works on my bike at least. Anyway, over here vapor lock is not such a big problem, at least not in the forums. With cycling I mean let it pump the 2 seconds given by the ecu, then again and so on. Should this fail you could also open the pipe to the regulator and let the pressure out, together with quite some mouthful of fuel of course what maybe makes this procedure a bit risky.

 

Hubert

[jrt]

I think what Hubert is saying is to listen to the pitch of the electric fuel pump. It will be lower pitch when it is pushing liquid fuel, but run faster and at a higher pitch when it is pushing vapor.

Leave the key in the on position, then turn the kill switch on the handlebar off. Turing the kill switch back on turns the pump on. The pump turns on (cycles for 2 seconds). Do that a couple of times.

[Lawrence]

I think what Hubert is saying is to listen to the pitch of the electric fuel pump. It will be lower pitch when it is pushing liquid fuel, but run faster and at a higher pitch when it is pushing vapor.

Leave the key in the on position, then turn the kill switch on the handlebar off. Turing the kill switch back on turns the pump on. The pump turns on (cycles for 2 seconds). Do that a couple of times.

 

Thanks JRT, That's what I figured, but wanted to be sure he was suggesting that this procedure might actually clear the "bubble".

[stormsedge]

Have you tried opening your gas cap as soon as the motor dies of suspected vapor lock? If you hear a hissing and see the tank expand, check the routing of your vent tubes on the bottom of the tank to ensure they are not kinked. You may be experiencing tank suck-starving the fuel pump.

 

I've had the tank suck...but not a vapor lock even in many miles of over 100 degree heat.

 

After you park, the cylinders will tend to be a great deal hotter to the touch than when the motor is running with air flowing across them as you ride. If I can lay my gloved hand on the rocker cover at 50 mph without having to quickly pull away, I call it good. I don't touch it when its sitting still. That said, if your fuel line is cool or easily handled, then it wouldn't seem (to me) a likely candidate for vapor lock.

 

You can verify your oil pressure by removing the sending unit and attaching an inexpensive oil pressure gauge. Then crank her up...or, remove the plugs and spin your motor on the starter for a few seconds if you really think you've lost pressure. When did you last change the oil filter? Might it be loose?

Cheers. k

[luhbo]

.. but wanted to be sure he was suggesting that this procedure might actually clear the "bubble".

 

Yep, be sure about that. This procedure can clear the bubble. It did so several times for my bike. Usually when I come back from paying at the gas station. It seems to be a combination of hot days, a hot engine and a really empty tank.

 

Hubert