How do I install a fuel filter?
Installing an inline fuel filter is recommended as an extra safety measure against dirt and rust particles from the gas tank clogging up the carburetors. The installation procedure is simple and should be one of the first things you do to your bike.
Finding a filter is easy. Any generic filter of a size that will fit in the space between the petcock and the carb fuel intake will be fine. Get one with a transparent plastic body, so you can tell what's going on inside of it at a glance. Make sure you're getting a filter for a gravity-fed fuel system, and not one designed for a fuel pump, which won't flow enough fuel when your tank gets low.
You need a filter that fits 1/4" fuel line. These are readily found at any auto parts store, even out in the boonies. The ones that will fit in the space your Ninja provides will most likely be designed for riding lawn tractors or other such machinery. Motorcycle stores will also have the right thing, usually hanging on a piece of cardboard marked Vis-U-Filter. They're usually less than $5.00 each.
The connection is a simple pressure push-fit (and it will be tight), but for extra security a spring clip or hose clamp (such as those below) can be installed at each connection.
If your bike is a 2000 or newer model, it should have come with an in-line filter. It's very small, and is located in the fitting on the carb end of the fuel line. It's very hard to see, and most people don't even know it's there. Since it's so small, and you can't see what's happening inside it, it's of limited use. You could take it out and clean it periodically, but that is inconvenient, smelly, and unnecessary.
If it looks the one below, tossing it is the best bet. Actually, it's so small and so easily clogged that tossing it is the best bet in any case, as long as you're adding an external one as described here. New OEM filters are $13 apiece; for that you could buy three or four of the aftermarket kind we're talking about.
The following pictures show the location of the stock filter. Remove the fuel line from where it connects to the carbs. It will probably be a little tight. If you press forward and then pull back with a little twist it should come loose.
The photo below shows the relative size of the OEM filter vs. a smallish replacement. Which one do you think will do a better job of filtration?
Installation is quite simple:
Figure out where you want it to go. Orientation (horizontal, vertical, diagonal) makes no difference. There will probably be some fuel in the lines, so drain that out. Cut enough hose out so the filter will fit between the two cut ends of hose. You will probably find this easier with the whole fuel line off the bike. Be conservative; you can always cut it again. If you want to be really safe, buy a short length of fuel line and use that, keeping your stock line intact.
The filter should have an arrow on it. This shows the direction of flow. Point the arrow toward the carbs. If there is no arrow, the bigger/wider part of the filter goes toward the carbs.
Put the clamps or clips on the hose and tighten them to secure the connection to the filter. Remember, it's a plastic filter. Don't get carried away with the tightening. Put the fuel line and filter assembly back on the bike if you took it off.
Start the bike and check for leaks. You should take the bike out and run it at high rpm, just to make sure the filter will flow enough fuel to maintain high speeds.
One very important thing to remember: Carry a spare filter AND a bypass with you when you ride. A bypass is simply a piece of plastic pipe the same size as the filter outlets. It will join the two ends of your hose together in case you need to remove your filter in an emergency. If your filter clogs, this may make the difference between a quick fix on the roadside and having to call your significant other to pick you up. No use ruining both of your days.
Filter maintenance is quite simple: Replace and toss. It is recommended that you replace your fuel filter once a year. Just like the oil filter, it picks up dirt and other unwanted stuff that should be thrown out. Also, the plastic in these filters tends to start to break down after two years or so. Replacing them is cheap insurance. We still recommend plastic filters, as you can't see through metal ones.