hi all think this has been ask before is there anyway you can put decals on a plastic tank?

Yes, it's possible if the tank is painted and has a smooth surface, like on the 199b models:

Original there where transfer decals mounted to the gas tanks of the 199b that where additional coated with a clear coat, the tendency that there will occur bubbles due to gas fumes is very high. Nowadays there are standard decals too available that you can mount without clear coat, these will last longer. Non of them will stick to the standard plastic gas tank as it has this special rough/textured surface.

Gas tanks 199b, behind original with bubbled of decals, some homemade paintings, ... foreground:

NOS Bultaco 199b painted and with decals (Italian model, no Sherpa sign on top):

To the solid colored plastic tanks with the textured surface, these logos where printed to the surface, as there are no punch/chop available anymore, you have to spray them on I would guess and you have to make your own jigs for this too, ...

This will work for the main side logos but not for the logos on the top.

Textured solid colored PE gas tank with stamped on logos:

The aluminium gas tanks that where very commen in your country would be the best solution, depending painting and decals.

hi thanks ill think ill just leave it for know

Good idea, getting a proper working gas tank, leak free, ... is first duty, mounting any decals is freestyle and can be done later too.

Freehand painted "decals", as you might probably have seen on the photo are not so well in appereance.