I bought a parts bike for $80 last week, and once I got all the dirt and bugs off the tank and side covers, they turned out to look in really great shape. The tank is spotless inside- clean metal, and not a bit of rust. The only thing is that it had this horrible pin striping and custom script that said "Cadillac Pussy." What that means, I have no idea, but it had to go.
At first I tried acetone, but that had zero effect. Then I read about pin stripers using Easy Off oven cleaner, so I went to the grocery and bought a can. I did an initial test leaving the oven cleaner on the tank for about 10-20 seconds, just to make sure it wouldn't affect the paint.
Untitled by
kennyredman, on Flickr
Then I left the cleaner on the tank for about a minute or two, just to make sure the paint would still be ok, and a little bit of the pin striping started to come off...
Untitled by
kennyredman, on Flickr
After I was sure that the paint wasn't going to be affected by the spray, I left it on for about 5-10 minutes. This time, the pin striping wiped off easily and the base paint job looked great. There is a tiny bit of ghosting, but I think that'll clean up once I give it a good wax and possibly another coat or two of clear.
Untitled by
kennyredman, on Flickr
Untitled by
kennyredman, on Flickr
Untitled by
kennyredman, on Flickr
So, I'd recommend using the oven cleaner to remove any pin striping or custom paint like this from a tank with factory paint or a two-part urethane paint.
Here's the whole set