Fixing a frozen bike quill handlebar stem
I didn't have any luck with heat cycling or using penetrating oil to free my stuck quill stem, and I didn't want to sacrifice it. I used the mechanics' trick of automatic transmission fluid and acetone mixed 50/50 as a penetrant. I dripped it into the steerer tube from the bottom and painted it onto the stem. I let it sit for half an hour and was able to free the stem. Hope it works for someone else, too!