I have a '94 honda shadow 600 and would like to know how to remove the fuel tank.

John, they may not of had a replacement at the time and that filter may have been bad. Make sure you add one if there is not one presently, to save potential problems later. They have a screen type filter in the tank also it is connected to the Gas valve/switch.
Check the attached links,instruction and guides, Good luck
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replacing fuel filter

2006 honda shadow 600 vlx fuel filter Google Search

How did you check the petcock? sure its not that.Yeah swap coil packs then ask again.

Anti freeze according to Honda's instructions ... gas treatment, get a recommendation from Honda or from your auto parts store. There is a complete list of other things to consider in your Honda Owners manual ... if you lost yours ... go to http://hrca.honda.com/ and find your on line version.

Best way to do the gas is treat a full tank with treatment, go around the block ... maybe a little more ... turn off the fuel valve and let the engine run until it stops. Remove the plugs and treat per the manual instructions.

Thanks for your question at FixYa.com

Sand the points under the black cap on your fuel pump. when the corode it will act like this. It cost nothing and it worked for me.

It sounds like time to clean the carburetors. Just for fun, remove the screw on the side of the carb float bowl. Is gas even getting into the carbs? Check the fuel valve on the tank. Is gas flowing freely when the valve is open? I would install a set of new spark plugs and add an in-line fuel filter also.

should be a bolt at the back of the seat,(some are under fender, some on top) remove it , press front of seat down and pull backward at the same time