There are a few options, You can do what a lot a people do and use your eye-balls or; do the ol' "wait till it sputters 'n' switch over to reserve" or; watch your mileage and know how many "miles per gallons" you get or; go to eBay or your local cycle/junk yard and find a tank with the sending unit already in it and wired to go or; do a search on the net like,
http://www.all-honda-shadow.com/dire...e-cluster.html .Good luck.
It takes a few seconds to load, but a good link.
