When I first got the bike the gas in it was visible brownish now that I'm running only non ethanol the gas after several tanks full the gas in the tank is clear no idea how long old gas was in it. What are my low cost options ?
Drain the tank, get a flashlight and a small mirror. Look around for areas of surface rust. Small areas with minor surface rust can be dealt with. Bigger areas of flakey rust or pitting aren't so easy.
Easy way...
1) Drain the tank and dry completely.
2) Visit hardware store and get muriatic acid, some stainless steel nuts in various sizes, latex gloves, and 2-stroke engine oil.
3) Visit grocery store and get baking soda.
4) Put the acid and the nuts in the tank, being careful not to spill it. Seal the tank, but leave a small vent hole so vapor can escape.
5) Shake the tank so the nuts rattle around and help knock loose any rust. Rotate the tank so all inner surfaces are affected. Do this for several minutes. Your arms will be tired.
6) Drain the acid and the nuts.
7) Flush the tank with hot water.
8) Look inside the tank and see if the rust is gone. If not, go back to step 4.
9) Mix up baking soda and warm water, and add to the tank. Slosh it around so all surfaces get touched for a minute or two. This neutralizes the acid.
10) Drain and rinse thoroughly with hot water, really hot so it'll flash dry.
11) Mix up the 2-stroke oil with 100% gas something like 15-20:1.
12) Add that to the tank and slosh it around so all surfaces get coated. Let it sit for several hours (overnight), sloshing it occasionally.
13) Drain that and rinse with some pure gas.
14) Reinstall and hope for the best.