Saving Old Seagulls

Spent a lot of hours getting my t.c ready for final testing, but the tank is full of green scale and sludge. I've tried all manner of flushing, but bits still emerge. Is there a solution that will dissolve this? I am convinced that if I get this right she will start on the 2nd or third pull at least.I was 8 yrs old when engine was built, and I have every confidence in it!
Thanks

Have a look here

viewtopic.php?f=2&t=6123

Thanks Hugz, I didn't see those posts when I was brousing before.
Red