Will acetone have an adverse effect on the oem tank liner (it's orangeish)?
When I restored my fuel tank it was full of huge orange blobs of crap. I'm assuming that the leaded fuel which used to be in the tank had evaporated and trashed the OEM tank liner. If your tank is in the same condition that mine was, it'll probably smell like varnish inside.
Considering that there already has been an adverse effect on the OEM tank liner, I'd go with using acetone to clean it out. Let's face it. The original tank liner has already been compromised and so your tank will need a thorough clean out. There are many ideas on YouTube explaining how to do it and what to do it with.
Once the tank has been cleaned out you can either put a new tank liner in it yourself, or pay a motorcycle restoration shop to do it for you. I opted for the latter because it was recommended that the tank had to sit for 24 hours whilst full of sulphuric acid before a new liner could be installed. I thought if anyone is gonna get chemical burns, it ain't gonna be me. Been there, done that!