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Inline Filters
by Gary LaPook(Originally posted to the XS list on 8/22/99)
I installed two inline fuel filters a couple of months ago which I bought for $1.50 each at the auto parts store. They are clear plastic, about 1 1/2 inches in diameter and about 3 inches long. Judging from all the red particles already visible inside them I am sure I saved my carbs from indigestion.
I first mounted them on their sides above the "airbox-to-carbs boots" but then discovered a problem with this arrangement. If I ran the tank dry (until I noticed a loss of power) before switching to reserve a bubble would become trapped inside each of the filters which choked off the fuel flow by limiting the area of the filter available to pass fuel. I decided that there had to be a better way.
I went to the auto parts store and bought about 4 feet of fuel hose, its cheap and it is better to have too much that too little when working on a project. The diameter of the filters was small enough that they would fit in the gaps between the "airbox-to-carbs boots" and I placed one between #1 and #2 and the other one between #3 and #4 leaving the gap between #2 and #3 clear. The filters are mounted vertically with the large end up. The fuel flows through the filters from the bottom up to the top and on to the carbs which allows any bubbles to escape through the carbs without any problem and without notice.
The way I routed the new fuel lines was from the petcock down through the gap between #2 and #3 "boots" and and to the bottom of the fuel filter on the opposite side of the bike. I then ran the line from the top of the filter to the carbs back on the opposite side, on the side where the line started from the petcock. I turned the fuel line fitting mounted between the pair of carbs "UP" (they rotate easily) to make it easy to connect the fuel line. I then repeated the process on the other side. This hose routing makes for smooth curves without any sharp bends that could interfere with fuel flow.
Another reason to use longer fuel lines when you install the filters (and even if you don't install filters) is that it makes it easier to synchronize the carbs. With longer hoses you do not need to remove the gas tank or arrange a temporary tank when doing the synchronization because you have enough slack to just raise up the rear of the tank so that you can get access to the adjusting screws. Just remove the screw at the rear of the tank and prop the tank up in back about 4 inches. I use a short piece of 2 by four to hold it in that position.
This setup has been working flawlessly for over a month now and I recommend it to everyone. See the diagram and pictures for details.
In the photos you can see the tops of the filters between the boots and the hoses.
Good Luck!