I got a sticky problem!

Boy, that's a new one. You shouldn't have had any trouble at all with 161 over MTK. I've done it several times with no problems. Plus, as you say, it's OK per the tech sheet. It should also be OK over bare aluminum. I have used others clears over bare aluminum but not specifically the 161. The 161 should dry fast - to light touch, usually within a couple of hours after application at normal temperatures. Did you wait the 4-6 hours minimum after the MTK to clear? Are you positive you used the correct hardener in both the MTK and the 161? They use the same hardeners but the 161 uses twice as much (2:1 instead of 4:1) and does not use a reducer. Is the drying problem only over the MTK or is it also over the bare aluminum? If it's over both, then I would expect an issue with the clear, most likely in the mixing - perhaps not enough hardener? Unfortunately, I don't see an easy fix. It would seem that stripping and starting over is the best course of action. Perhaps someone else has another suggestion.

Rod