These holes in the switch are preety substantial but the screen is fine plastic mesh.like 3mm. may be clogged with rust if tank was real bad and filter was broke. Check in all settings (pri,on,off, res, whatever) and see if that helps. Otherwise you may have to drain the tank and check the petcock (he he I said . . . whatever) for clogging. Done this a couple of times, when they are old they can be fragile, so be careful with the filter. Then again I am the kind of guy who would try to fix my cell phone if I had any chance of being able to fix it. the filter is about 3-4 inches high so slosh the tank around see if you can dislodge anything stuck to the filter, and please no smoking while doing this type of work. May want to open a window unless you like that kind of thing.

A friend and I both owned 150cc United Motors scooters.  This was my first introduction to the vaccum petcock.

I pulled the fuel line from the tank to the carb one day and "no gas", but I had read one of the tech. manuals and vaguely recalled something about a petcock, so I had her turn it over with the starter.

Result:  gas EVERYWHERE!

Good thing neither of us smoke ...LOL.

update: im not very familiar with how the vacuum works or anything since this is my first time working on a motorcycle. i tried to find threads regarding it but sadly im not very good at navigating forums so i came up with nothing. the line that i have disconnected is the line leading from the back of the petcock towards the carb. the line that has a spring wrapped around it is connected to the carb still. i tried to undo the fuel line, put it in a bucket and start it to see if it would shoot out gas like one person said and nothing. im not really sure where to go from here =/

yeah, actually i had tried that. if i pull the petcock do i actually have to drain the tank? can i just flip it over and be careful? lol. i just dont want to have to drain the gas i just put in there from the top again >_<

The spring covered line is the vac line, it goes from the right side of the carb to the back of the petcock...
The front of the petcock is the fuel line it comes out  horizontal and goes to the left side of the carb.  It should only flow gas in the prime position.

The engine must be running to let gas flow from the on or reserve position....

reserve will do the same as on when the engine isn't running.
they are controlled by vacuume from the engine.


try prime, gas should flow whether the engine is on or not.

sorry, i meant i tried it on prime =P im definitely learning alot more about what those settings mean though lol