I've been hearing really good things about Caswell's
http://www.webbikeworld.com/t2/caswell-fuel-tank-sealer/
Not sure where to get it though.. checking on that for ya.
You can order it directly from Caswell.
It works better than the Kreem. I have used Kreem on 5 tanks.
On the 5th tank the Kreem reacted very poorly and had to all be removed.
A real pain. Took many hours to get it all out. Luckily the tank had been sitting for about a month or so after I thought it was finished, and one day I noticed itwas all cracked and lifting, just as I was about to install it.
The Kreem tech support was non exsistant.
The Caswell product has people that answer the phone and are very helpful.
The only thing about the Caswell product is it is a tranlucent amber color and so I added a white colorant that I got from TAP plastics and Caswell said it would be ok.
I bought the better grade of colorant from TAP plastics for epoxy.
The directions for how much to mix for the tank were off.
Mix the entire kit for a Honda CB750 because the tank has lots of surface area.
Plan to spend about one hour after you pour it in to roll the tank around and get it all covered. Use a bright LED small flashlight to check inside the tank.
After you get it all covered keep repositioning the tank about every 10 minutes or so until the coating has set up.
On the 1978 5 gallon CB750 tank I had no leftover coating to pour out and it was nice and thick and glossy.
I applied it over a rusty but smooth surface as per the Caswell advice from a technician.
The colorant was about $6.00 and worth every cent.
Below is a photo of the Caswell liner which is thick hard and glossy white with the colorant added.
I will post a photo below.