The nut on the top is 9/16 SAE. Disconnect the WIF plug, drain the filter (I capture mine in a clear qt jar for examination) loosen the nut and the filter housing will drop down. I rest it on the frame and remove it from underneath using the space near the firewall. Discard the filter and the o-ring that is attached to the enter post of the housing. I recommend removing the circular brass nut, push the old bolt out the bottom and replace it with a grade 8 bolt from a good hardware store. The stock bolt on mine broke one hot summer afternoon in the Alabama boonies. I lube the new o-ring and seals with petroleum jelly (Vasoline). Reinstall the housing. Make sure the drain lever is facing forward. On the top of the housing is a 10mm bleed bolt. Remove it and pump the canister full of fuel with the manual pump. About a million strokes will do it:-laf It is full when fuel comes out the bleed hole. Replace the bolt, then pump a little more until you hear the over flow valve squeal. The engine should start easily.