I received my gas tank from my brother this week. He painted it as a project to learn how. He did a great job! However, we didn’t think to mask off the outside from the inside so there was overspray inside and the neck was painted also.

We figured,ok, just rinse with fuel to remove anything loose. So i did and then mounted it with an nos cap also. The next day I thought I’d check inside and this is what I found:

So I took an xacto to it and removed all loose paint. I’m thinking it’s time to soak with acetone to remove all paint inside. My question is, should I remove more paint from the neck? An if so, just to the outside of the sealing surface, or something else. Obviously the paint is not fuel proof as the fumes were only in there less than 24 hours.

I would remove the new paint from the top sealing surface of the filler neck to prevent lifting from beginning under the cap and spreading out towards the area that is visible on the neck. On the outside of the neck, and tank in general, the paint should be fine as long as it isn't exposed to fuel for extended periods of time. Always wipe up any refueling spills promptly.
Looks beautiful!

That was my thinking also. We (mostly brother) have filled and painted it twice over the last 4 years. Mainly due to not reading the directions the first time.
Thanks for the compliment! Tried to do everything right the first time, or second,.... possibly a third.....

Acetone will ruin the paint pronto. You have to be REAL careful if you choose acetone. I don't think the new paints are "fuel proof" at all. If you drop some on the tank you can wipe it off with a damp rag and be ok but constant exposure to gas will cause the paint to loosen. When I first got my bike (it was painted in 2014 but sat for 5 years) I saw that the paint was loose around the filler neck. Several others I have seen were the same way. Beautiful paint job, please be careful with the acetone.

Thanks for the heads up! My problem is that there is overspray built up inside that is going to wreak havoc with the fuel system. We didn’t close anything off. I will go to the nth degree to protect the paint. I think I’ll completely cover the outside with a plastic bag to protect the paint.

A little update:
Thanks to those who cautioned against acetone. Instead I shaved the paint back on the filler opening and petcock area. When I reattach the petcock, I’ll use yamabond outside of the o-ring to form a barrier between paint and fuel. I soaked it in gas for a bit today and rinsed it out hopefully I got the majority of the loose stuff. Guess I’ll be keeping extra fuel line filters in my tool box.