Fuel petcock keeps cloging, any solutions?

[3 on the Tree]

So I took my '81 ATC 200 out for a romp today with some friends. I've cleaned the carb twice on this thing in the last year because after a short run period it would always die on me. I couldn't figure out why and at one point I even thought it was the coil.

I ultimately found the problem today; the petcock (screen, I think) keeps getting clogged. I have a clear fuel supply line on it going to the carb and I can see that the fuel is barely coming out, if at all; even when on reserve. Several times on the trail today I had to remove the tank and blow backwards through the petcock to achieve flow again, even then it would only be minutes before the fuel supply became a trickle once more.

The petcock in the tank is a NOS piece I installed last season and it is in the original steel tank. I never see any sediment in the tank or unusual colored fuel in the line, although the tank does have some surface rust inside. Is it possible that I have just gotten a bad petcock, or is it the maybe the screen getting clogged? It is very hard for me to blow through, regardless if I have it on "on" or "reserve". Should it be like that? Maybe the vent on my gas cap isn't working properly and it's causing this?

[MuckUte]

Checking the fuel cap vent is easy, just take the cap off next time it stops and see if you get fuel again. I've had trouble with tanks that looked ok but when i flushed them out had quite a bit of junk in the bottom so maybe taking the tank off and giving it a rinse may not hurt

[Kintore]

If that doesnt work, some people use muriatic acid and/or ball bearings and shake the hell outa it. This is will free most of the rust/dirt outa the tank. Make sure you flush it out very well and wola! RUN IT!

[3 on the Tree]

Thanks guys. Yeah, I don't think the tank is bad enough yet to the point where it needs creamed. I am going to use a bunch of small nuts and bolts to throw in the tank and maybe some acid. Hopefully that puts an end to this annoying problem!

One last thing, would it hurt the petcock/screen if I blew through it with a blow gun and compressed air once it's off?