Help with Stihl 028AV bogging

[7river]

I have a 028AV super. It boggs down when I give it full throtle or under a small load. Fuel screen looks clean.
It was stored with fuel in it for a few years but it seemed to recover from that...maybe not? It ran fairly well for a few tanks before the problem started.
I imagine its something simple but I just don't know these saws (although I love the saw)
Any ideas?
Also anyone know of a good repair/troubleshooting manual for chainsaws and such?
Thanks
-ron

 

[Fish]

Take the carb off again, and remove both covers and the needle/spring/lever.

Hold it up to a light and look through the passage under the needle.

 

[Rookie1]

When you say fuel screen do you mean you took carb apart or filter in tank. Like Fish is saying there may still be junk/varnish in the fuel system.

 

[7river]

Thanks for the tips.
I will take the carb off and go through it. (I have not taken it off yet. I only checked the tank filter screen)

 

[Fish]

There used to be a foam insert in the fuel filter. After 30 years or so, the foam breaks apart and collects in the screen inside the carb like a wad of snuff, and the passage underneath is clogged up as well.