Need to seal my petrol tank as I keep getting constant CRAP in my carbs, 2nd time I’ve cleaned them in a week…
Seams no one local to me sells it…
Have you found a hole?
Take a look inside your tank when its empty and see if its rusty.
Sounds more like a breather pipe is missing ,thats the usual cause of mucho crapo coating a bike engine .
I was guessing it was rust and general age of the tank,
After draining the fuel out, it seems the fuel I put in from my shed may have had some water in it… 
I’m going to start a thread regarding that…
clean your tank out too if you do the carbs.
Also worth fitting a filter between the tank and carbs? Cost pennies and worth every one of those. Oh. Also worth carrying a spare under the seat for if/when the damn thing clogs up
Fuel tap has a built in filter.