If adding one filter is good isn't adding, like, 5 extra, even better? Just think how clean your fuel will be!
Do you care if particles sized 0.002" flow through your carbs and out the exhaust? Would that harm anything? Would you even notice it while driving? Your filter has to stop particles from getting to the smallest orifice the meters fuel. Usually, that's your slow jet size. All the stock Honda filters that come with the bike block particles that can harm carbs.
Adding extra filters, also adds extra maintenance. Even if your added filter blocks finer particles than the Honda supplied one, where do they go? They stay in the filter, which you have to clean or replace periodically or it gradually and incrementally reduces fuel flow capability. When do you find out that this has occurred? On the freeway when you engine overheats and holes a piston due to progressive and repeated fuel starvation?
The early Honda petcock filters have a sediment bowl, that once a year, you remove, clean and reinstall. The bowl splash flushes the screen to keep it clear and flowing (unless your tank is hopelessly rusted). The screen prevents particles that won't fit through carb orifices from reaching the carbs.
The later Hondas have an in-tank filter that blocks even finer particles than the earlier type. There is no sediment bowl, the sediment is held in the tank. The sloshing of the fuel in the tank constantly clears the mesh so proper flow in maintained (again, unless your tank is hopelessly rusted). It still won't allow any particles to reach the carbs that can block metering orifices.
If your stock Honda filter is installed properly and functioning as delivered, you don't need another (or several more) filters on your bike.
As mentioned earlier, the fuel feed from tank to carbs is done with gravity. Any plumber worth listening to, will tell you that such systems need a constant grade reduction to flow properly. Loops and dips in the line, trap fuel or air. When the tank level gets low enough to the drain, either the bottom of the tank on reserve, or the stand pipe height, the head pressure falls very low, such that an air bubble trying to rise, can block fuel flow, or worse reduce fuel flow, leaning the fuel mixture. Honda doesn't provide much room in many of their bikes to insert a useless filter, without adding a fuel line loop.
That's the science of it. However, if adding filters is a religion for you, or a habit like locking your door three times, you'll gain peace of mind by adding an extra fuel filter...or three. It is something fairly easy to do to make operators feel they've done something nice for their machine... like the best oil they can find.
Cheers,
