Whatever you decide, as an interim measure a good magnet either inside or outside the tank might keep most of the rust from going down the pipe.
We have been having good luck with tumbling tanks with small pieces of chain, ball bearings, and nuts inside to break up the loose rust then rinsing the tank out with water and then acetone. Sometimes several repetitions of each step. Solder or braze the big holes and then we then use a product called Red Kote to line it. It has worked well for us so far on many antique tractor tanks and I just recently lined my D6 pony tank with it.
Two compounds I know the name of are Red Kote and POR-15, but there’s probably others. I think it’s best to line the pony tanks while you have them clean. I’ve had to do some extensive brazing to save one that I should have cleaned and lined a long time ago. I’ve redone one pony tank after 10 years and it worked just fine the second time. Maybe I didn’t get it cleaned well enough the first time.
Which ever product you use the biggest cause for liner failure in any of them is failure to follow directions to the letter.
I have used POR15 products with success on several tanks and so far all is well. Their cleaners, as I am sure some others, are water based which made sense to me after all the idea is to clean petroleum products out so why introduce more.
Good luck...….Bill
I second Bill's comment - follow the instructions to the letter for the tank liners
I personally had good luck several years back on an old 8n tractor gas tank by filling it with about a pound of bbs and then rolling it around to beat out the rust. You dont want to spray anything oily inside if you want to use the red kote or any other liner product but it worked very well and I never had to repeat again. Oh, I did wash it out well with warm water also and let it dry good after removing all of the bbs and rust. Good luck and follow manufacturer specs
Thanks everyone
This is a 10-12 gallon tank and there is a layer of sand like or fine dust like rust on the bottom of the tank, no hole that I know of....yet. I just recalled the problem last year is the needle wouldn’t seal after the ride over. Stephen’s idea of the magnet/magnetic filter would have helped here.
So it sounds like the consensus is these home applied liners fall due to poor prep and not following directions.
It looks like I will order the KBS kit since it has all the parts needed and will ship to CA.
About 12 years or so back I had a small D2 pony motor tank with an inch of tar in the bottom and someone suggested filling it with gravel and solvent. Then tying it to a tractor tire and driving around for 1/2 hour. This worked great except one piece of basalite was a little oval shaped and took some work to get in the right position to get out of that little fill hole. The suggestion about using nuts is probably much better in that regard.
CR: I tried household lye to clean my D2 tank and it worked great. Bare metal inside now. It may seem unorthodox to some, but it was fast, effective and inexpensive.
Drilling the inlet of the fuel valve and installing a remnant of copper fuel line or even Synflex air line about an inch helps a lot too. Any heavy stuff in your fuel should settle to the bottom, and not get drawn into the filter. Cheap and easy.