Motorcycle Repair: Mileage problem, honda shadow 600, full tank

Question
I have a 99 honda shadow 600. Had no problem with it at all until last year. With a full tank of gas, I can only get between 35-52 miles with the valve set to "on", and there is plenty of gas left in the tank. I can switch to "res", & I can go 80 miles before filling up. A friend of mine said to cut the tube down that goes inside the tank. I can do that but I feel that's the spec of the tube. Anything else, I can do to solve the problem?

Thanks

Answer
i usually only answer questions on harleys, but I think I can help. Drain the gas and remove the petcock. There should be a screen around it. remove it. You will see a tube coming out of it. This tube is where the gas goes when you have it on the on position. You can shorten it a little and the gas will drop lower before haveing to go to reserve.
Good luck and happy riding
Mike