Build a Cheap and inexpensive
Aux Fuel Tank
by Jack Frisby
When you have to remove the gas tank to tune your carbs you sometimes need a source of fuel so you can run the bike for an extended time.  There are tanks available that are made specifically for this but are priced around $50.

I made a great one that works fine and it didn't cost me the big bucks like the one in the catalogs.  I ordered a racing catch can tank, SUM-G1474 , $14.50 from Summit Racing 1-800-230-3030 (it comes in colors, but that is the number for white so the gas level shows) .

It has a vent at the top and a petcock in the bottom. I took a hole saw and cut a hole in the top so I could pour the gas in.  
I took a rubber plug or cork the size of the hole to stop up the hole (optional, but you are dealing with gas).  Attach a piece of hose on the petcock on the bottle; add a clothes hanger wire hook around the bolts that are attached to the bottle and it's done.  It cost about $16 total and it even has its own petcock. Actually better than the ones they sell for M/C. 

Polyethylene, white, 11.5 in. long, 4.5 in. diameter, one quart capacity, overflow catch can
You can hang the bottle from the mirror or handlebar or from an overhead source.  If you secure the bottle you can actually ride the bike.  It would work for testing your jetting without having to reinstall the gas tank each time.