GUNK
The gunk you had in your gas tank is exactly what you have in your carb bowls. If you can pull the drain plugs and drain the stuff out that would be a great start. PERHAPS without removing them you might get out on the road and crank the throttle enough times to actually get the gunk through the carbs and get the needle valves and floats freed up enough to work properly...start it up and use the choke to keep it going, only enough choke to do so though and as it gets more time on it then keep moving the choke till it is completely off...as soon as you can...and just keep changing positions of the throttle and working it...IF it just won't work you'll have to pull the carbs and rebuild them, andthat is not fun, but it won't kill you eithter...bottom line is you will know for sertain tha tyou are getting the job done right when you get into it. If you are going to an aftermarket muffler and pipes you should rejet and that would solve the rejetting right there. Freakinout has a link or atachment for the carbs that he has posted...good luck on freeing them up...don't forget to clean and reoil your airfilter...