Oh heck Dozuki - that's not bad at all. There are all sorts of methods of cleaning that right up and having it look really nice at low cost.
I have used a product called POR15 which works great - but it can be a bit messy and its laborious (incidentially, it is the same stuff that Jay Leno uses on all of his multi-zillion dollar car restorations.
NOTE: I strongly recommend that you
NOT use a product called
Kreme as it seems to dissolve in today's fuels that often contain ethanol. When I was researching how to clean my first tank last year, I kept running into motorcycle shops that would do it for me using Kreme for $$$ - but I also kept running into people who said that this stuff is really bad news.
A number of folks on this forum have used much easier methods including one which simply called for you to block-up the fuel filler lid and the petcock openings and then do the following:
- put a handful of small stones (like aquarium gravel) or even a dozen or two roofing nails in the tank;
- stick it in your clothes dryer - which you will also stuff with old towels, sleeping bags, etc.
- with the heat OFF - just let it tumble for a day or so.
When you take it out - the rust should be off the walls of the tank and it will be nice and shiny new inside.
Now - you may need to stop the dryer and empty the tank a couple of times if there is a lot of crap in it - but the process really does work. It would work even better if you could figure out a way to really seal up the openings and put in some vinegar or even water.
Alternatively, if you poke around bike shops in your area, you might find someone who has a tank tumbler. I am building an XS650 cafe bike and am using an XS750 fuel tank for it - and one of my friends here built himself a tank tumbling machine. Here is a linky - and there is a YouTube video of it in action.
http://www.xs650.com/threads/build-thread-special-to-cafe-bike.48165/page-4
Again, as with the clothes dryer - the tank tumbler motion is pretty slow and relaxed - but over a few hours, the scouring action of the pebbles or nails or whatever really removes the rust amazingly well.