I'm repainting my bike and I'm running into an odd problem.... I've prepped and painted all the parts the same way (fenders, tank, side panels) by doing the following:

1. Sanded down the old finish down
2. Primed the surface, sanded it down
3. Painted 2-3 coats, wet sanding between coats with a finer and finer grit

I waited a good day in between painting the primer and paint, and then a day since the last sanding of the painted surface with 2000 grit sandpaper. I sprayed clear on the tank and the side panels today and while it took just fine on the tank and one of the side panels, the other side panel immediately started cracking horribly..

Here's what it looks like: http://imgur.com/a/0TMTG

You can see the good side panel in the first photo, the bad one in the second, and both in the last. I don't understand what I did wrong, both panels were prepped and painted in exactly the same way, with identical dying in between coats and the same exact cans of paint used on both.

Any ideas? At this point I'm thinking I need to sand it back down completely and start over...

My guess is that the nasty looking side cover was replaced and a quick paint job was thrown on it to make it match. What it looks like is the quickie paint started reversing and puckered. Your only hope is to sand the finish down until you get rid of the paint that's puckering, you may end up sanding down to bare plastic. Just curious what type paint/primer you are using, rattle can or catalyzed urethane? With a bit more work it will come out.

Rattle can unfortunately, can't afford the setup for the good stuff. It was already sanded down do the bare plastic. I'm guessing I did something wrong at some point.

Did you mix enamal with latex?

my side cover did exactly the same thing.. and I sanded down to bare plastic, twice

other side panel perfectly fine.

No, enamel with enamel. I specifically bought all of the same type/brand to avoid this issue.

Try a good prep spray like prep all.maybe grease.what's the cure time on the paint?maybe the clear was sprayed too soon?

I'm gonna sand it down tonight and start over. I didn't use a prep spray since I had sanded down the original paint - didn't think it'd be necessary. I'll give it a go since I need to pick up another can of paint now.

Grease and wax build up in the paint and stay on the surface as you sand

on mine, I used primer, color and clear, all same brand. time frame between color coats within what the manufacturer says (long enough to flash). clear coats was a minimum of 24 hrs. lots of sanding before paint (as I said, took the plastic parts down to bare plastic).

Note: when mine first did this, I redid all steps (including taking it back down to bare plastic), and redid the primer, sand, primer, sand primer, paint, paint, sand, paint, paint, let dry good, then clear, clear, sand, clear, sand, clear. same exact result on that cover.

well, the exact order and number of paint/sand and such may not have been what I posted, but it was similar to that.