Valk running intermittantly

[Mulepick]

    16065.1
My 98 will be doing fine then just lose power.  I pull over and engine goes off.  I turn it off, turn it on a minute later and with a couple of burbles starts up and runs fine for the rest of the day.  This isn't the first time something like this happens and I have had it in to get carbs cleaned, adjusted, etc but it doesn't fix it.  I have an aftermarket petcock that works fine.  Sometimes I light it off when cold and the two front cylinders don't fire.  Turn it off and the next day things work fine.

Any ideas?

[Michvalk]

Check the vent tube for blockage. Runs from the back of the tank down through a T without anything on the one leg, and out the bottom. Might also check the petcock vacuum line for cracking. Then check the petcock with a vacuum leakdown test. There are several threads on this subject. Go to the main tech page, and put what you are looking for in the search box. But , you can try these things first, as it sounds like it's starving for fuel.

[gordonv]

If your aftermarket petcock doesn't have a vacuum shutoff, then it's not that. But it almost sounds like fuel delivery problems, and could be a non-venting gas tank.

Have a spare key? When the bike stops, open the gas tank cap. If you hear air rushing in, you have a venting issue. the bike should start up almost right away (after the fuel starts flowing again).

It also sounds like an electrical issue. I'm thinking a harness coupler not seated fully. Does this happen when dry or wet (rain)?

Others, could it be the main coupler behind the motor at the lowest section of the frame?