Random engine failure - petcock? fuel tank?

[jolomatic]

Riding allong... try to accellerate, and realize the bike is not even running any more.

Bike won't start. Switch petcock to 'reserve' and bike starts.
Switch petcock back to 'on' and carry on, no problem.
(btw: I had just filled the tank, so I was definately not out of gas).

This has happened twice, about two months between occurances.

So, my best guess is that there is some debris in my tank, that clogs the 'on' tube.
Switching to 'reserve' releases the vacuum keeping the debris stuck, allowing me to switch back to 'on'.

I have no basis for this theory other than my purely theoretical understanding of how a gas tank/petcock works.

So... is there anything I can do to address this that doesn't involve reomoving the tank and shaking it upside down?

Might I be barking up the wrong tree entirely?

So far, it's happened on the highway in situations where I was able to safely pull over and deal with it... I'm afraid it may happen at a much worse time if I don't deal with it now.

Any suggestions would be welcomed.

 

[AGAVE]

Riding allong... try to accellerate, and realize the bike is not even running any more.

Bike won't start. Switch petcock to 'reserve' and bike starts.
Switch petcock back to 'on' and carry on, no problem.
(btw: I had just filled the tank, so I was definately not out of gas).

This has happened twice, about two months between occurances.

So, my best guess is that there is some debris in my tank, that clogs the 'on' tube.
Switching to 'reserve' releases the vacuum keeping the debris stuck, allowing me to switch back to 'on'.

I have no basis for this theory other than my purely theoretical understanding of how a gas tank/petcock works.

So... is there anything I can do to address this that doesn't involve reomoving the tank and shaking it upside down?

Might I be barking up the wrong tree entirely?

So far, it's happened on the highway in situations where I was able to safely pull over and deal with it... I'm afraid it may happen at a much worse time if I don't deal with it now.

Any suggestions would be welcomed.

Sounds like the gas cap vent man.
If it happens again, loosen the cap a bit to see if thats the case.
Sometimes they are stuck shut from the heat, little rubber part inside.

 

[jolomatic]

Sounds like the gas cap vent man.
If it happens again, loosen the cap a bit to see if thats the case.
Sometimes they are stuck shut from the heat, little rubber part inside.

Makes sense, but my gas cap doesn't twist on - locks/unlocks with the key... I will take a closer look at the cap though, see what I can see.
Thanks for the suggestion!

 

[Tripletrouble]

Vacuum operated petcock? Reserve doesn't need vacuum to flow gas. Could it be a problemwith a bad/cracked vacuum line?

 

[jolomatic]

Vacuum operated petcock? Reserve doesn't need vacuum to flow gas. Could it be a problemwith a bad/cracked vacuum line?

Honestly, I have no idea - I figured it was gravity making the fuel flow.
(The theoretical vacuum I was talking about was from the suction on the tube from the gas flowing down).

Thing is, that after I switch to reserve, then back to on, the problem goes away.
Which is what makes me think it may be debris in the tank.

 

[TwistedKestrel]

Considering that you had just filled up with gas, I'd suspect the gas tank vent as well. Can't provide any insight on your bike specifically though.

 

[jolomatic]

Thanks guys, glad I checked here first - I would have been removing the tank this weekend, otherwise.

I'll do some research and try to figure out how to deal with the vent properly.

 

[bvickerd]

I had a similar problem with an old suzuki - checking the vent to make sure its not gummed up is a good start. If there is a vacum line disconnect it, try starting the bike and see if it creates vacuum pressure. If neither of these work, pull the petcock and check the filter screen to see if its clogged. If there is a vacuum line, there is usually a screen in the petcock near where the line connects, clean this as well. Sometimes these screens can get plugged by random crap, or gummed up by gasoline residue.
Good luck

 

[skapan]

The tank vent line may be plugged where it hangs down at the bottom of the engine - or even pinched by something else. Definitely sounds like the vent as it quits on the highway but not in town.

 

[AGAVE]

The tank vent line may be plugged where it hangs down at the bottom of the engine - or even pinched by something else. Definitely sounds like the vent as it quits on the highway but not in town.

That's not a vent my friend, it's the overflow for the carb.