Hi Reeves

Unfortunately I think the only way to solving your problem will be to remove the tank.
I may be wrong but I think you remove the back seats's back rest and the cover in the boot that covers the tank.
Bolt it loose and take it out.
The chain idea I think is also a good idea to get all the crap loose inside and make sure to flush it properly not to leave any of that stuff behind that will find its way to your engine.

Good luck