Only McFarlane has approval to replace the old less fuel-resistant O-rings with the latest fuel-proof flourocarbon O-rings.
Cleaning the Fuel Screen - The fuel screen is removed by removing the standpipe. The rubber tipped plunger must be unseated before the standpipe is loosened. Failure to lift the plunger off of its standpipe seat can damage the plunger. Pull the strainer drain knob as if you were draining the fuel bowl. Block or clamp the knob in this position. Insert a smooth round tool such as a screwdriver or punch in the standpipe cross-hole and unscrew the standpipe.