My 83 110 dies intermittently. What does the gas cap on/off selector actually do?

[turbowrenchhead]

I had it out on the ice on sunday and it would not run with the choke off. It also would die ever 4 to 5 min of running. So I switched carbs. Took it back out yesterday and ran better with the other carb. But it still dies. I would crack the gas cap and sometimes that was enough to get it running again. I would also pull the fuel line and let some fuel run out and it would start back up. The cap has a on / off selector on it. What is that for? Is it possible that fuel tank is creating a vacuum and it restricts fuel? The only thing I can think to do it take the cap off and put some plastic around the hole and put a hole in it for venting and see if that cures my problem unless someone else has a better idea.

[Tecate Karl]

that is to shut the breather on the gas cap so your gas doesn't evaperate or let the air get to it and make it go stale as fast as a vented tank.

[turbowrenchhead]

So if its in the on position does that mean the vent is open?

[trikes4life]

yeah needs to be on to run, caps do go bad. i drilled mine out. until i got another one.

[MTS]

You pretty much hit the nail on the head That vent needs to be open to Keep the fuel flowing...Ever try and Empty a fuel can with the vent cap on???? Same thing...gravity feed, Has to Equalize the Atmospheric pressure difference...Or it creates a vacuum and will not flow...Like putting your finger on the end of a staw in a pop and pull the straw out...The pop will stay in it till you let off the finger....Make sense??

[3wheelrider]

yep-you need to replace your cap....

[turbowrenchhead]

How exactly did you drill it out?

[trikes4life]

How exactly did you drill it out?

Drilled a hole straight through the cap, Not enough to let gas out but enough to let air in.