Front brake locking

Took the bike out today and was just getting the feel for it since the front forks were done. Was doing a lot of stopping and going and getting a feel and then the thing didn't want to move. Well it moved, but rough. The front kept going down like it was stopping and it was struggling to move forward/backward. I give it some power and limped it home.

Watching the front brakes, the left side caliper started smoking. It was clearly dragging on the rotor. I checked it out and it's only the left side that's doing it. And it's not all the time. Actually had it pretty good for a little while, but it still locked up after some time. It just randomly comes and goes.

So, what causes this, and how can I fix it? Why just the one side?
Thanks!

Caliper body and piston can be corroded together or kinked/colapsed/plugged brake hose

Well the thing was fine at certain times. If I took a screw driver to the caliper it would be fine right away, lock, and then be fine again. Sometimes worse than other times though. And I'm not talking locked as in can't move it at all, but enough to where its hard as hell to roll.

Been reading to change the fluid and flush the brakes lines. Think I should do that first and see what happens? Lines look good by the way.

I wouldn't mess around when it comes to the brakes. It's hard to say what's causing the lockup, so you ought to go ahead and rebuild the calipers & mc. If the pistons are pitted, you may have to replace them. I don't know how much pitting would be considered acceptable, so I replaced mine. The Rr brake probably ought to be done as well.

Some of the rebuild stuff is still available from the dealer.
I installed K&L parts from Z1Enterprises.com (K&L = made in Japan & oem quality imho).

If they are the original lines, replace them w ss braided - old rubber hoses can burst.

I am going to get the rebuild kits for everything. Was looking at new lines from the start too. Inspected the hoses and they are all in great shape (visually)

I did a lot of research and seen that the piston could just have had some gunk build up causing it not to go back. So I opened the MC and the fluid is black, so will flush that really well. I pulled that caliper off and inspected, and it had a lot of gunk around the boot of the piston. Cleaned it all off, pushed it in and pumped out a couple times and went from hard and choppy to smooth after 3 tries. Reassembled and made sure fluid levels were good and so far the thing has been fine. There's a slight drag, which apparently is normal, but can still move the bike and rotor is not getting hot because of it.

So for a temp fix, it seems fine. But like I said, I will take care of all of it all and hopefully will be good.

If you only have a piston(s) on one side of the caliper,
then it sounds like the caliper "sliding" bolts are gunked up,

TWIST them out carefully,
clean them with brake or carb cleaner,
lube them with some kind of hi-temp grease.
TWIST them back in carefully,(The boots they go through act as seals)

IF thats your problem,you should be good to go.

Thats the way Z1s and KZs are.

Be careful and take your time.
Remember,,,they are your brakes,,,YOUR LIFE DEPENDS ON THEM

Mike