For your plugging filter problem, have you replaced your fuel line from tank to filter/pump? As for the tank itself, honestly your best bet is to remove it and clean it that way. Also replace or clean up your fuel shut offs. It's easy to remove the fenders and tank to clean it. 4 allen bolts holding the seat on, 4 more bolts holding the fenders to the foot rests and it's off. Takes maybe 10 minutes. Then the tank should just slide up and out.
As for your deck wheels, do you let yours ride on the ground or keep them a hair off the ground? I let the wheels skim the top of the grass, that way the weight of the deck isn't on them constantly leaving marks in the lawn from them. That's the only thing I could think of without pics.
So got any pics?
