Motorcycle caliper sticking, lever goes stiff?

Hi All,

I ride a Lexmoto XTRS 125, which I use for commuting. It's a nice runner with one problem - the brakes. I recently purchased new front and rear brake systems, and installed them as my last ones got wrecked in the salt from gritter and the general weather. They run fine for a week or two, but now they're playing up - and I swear it happened overnight!

I went to the shop one morning, and it run fine - the next day I went to go to the shop, and the front caliper was holding onto the wheel, making it almost on impossible to move. The lever had gone stiff too, and needed two hands to pull it, just to get the brake light to come on - I left it for 6 hours before going home from where I was, and it was fine - it had freed up, but as soon as I used my brakes, it started again, until it had completely locked up, and the wheel didn't move at all - and I mean, at all.

Now i contacted the place i purchased the calipers from (CMPO) and they said I should put new fluid in, and apply some copper grease to the caliper pins. By pins i assume they mean these ( http://hvccycle.com/images/hvc200106-F.JPG ). Is there any other reason they could be locking like this?

With the other problem I had, kicking the caliper would un-stick it, but with this problem, it doesn't - I just have to wait an hour or so, which makes me think the pistons do need some copper grease, as they're taking a hell of a long time to retract.

I ride to and from work, and go out every Sunday to a meet. I do try to keep my bike clean, and the calipers do get a fair bit of attention whilst cleaning.

Thanks in advance.

Ash