How to pressure test gas tank ??

Question

Brand new custom gas tank for my bike,, manufacturer says to pressure test and seal inside of tank before paint ?? exactly how can I do this and they say to mount on bike also before painting ,, ?????

what type of sealant to use to seal inside of newly manufactured custom built gas tank for custom bike and how do I pressure test this tank ??

Answer 1

Some strange instructions there, it's probably a bad translation from Chinese or wherever the tank was made. I have seen some howlers on food packages.
I would translate as ; Check tank for leaks when first filled, cover filler hole when painting, i.e.avoid getting spray dust in tank, the only reason that I can think of for the last one is to avoid damaging the paint job when fitting it, but it's not very practical, paint it then fit it.
Seen on a packet of peanuts; Allergy advice, may contain nuts !

Answer 2

To seal the tank, use this stuff:

http://www.jpcycles.com/productgroup.aspx?GID=F7683D78-C1B8-4BE6-AE78-D9FFAA2AC53E&search=kreem&store=All&page=1

To pressure (leak) test, plug all openings (petcock, vent, etc).
Get an old gas cap, and weld (braze, silver solder) an air fitting to it. Use a bicycle pump (NOT AN AIR COMPRESSOR!) to pump NO MORE than 3-5 lbs into it.
Either dunk it into a tub of water (enough to cover tank) or run water over it, while applying dish soap (for the bubbling action), and look for leaks.