Tonight I attempted to change the rear brake pads on my 400ex. I drained the brake fluid, removed the caliper, and the brake pads.

The old brake pads were completely trashed.

The piston is protruding (obviously compensating for the old thin worn ones.)

Here's the problem. The piston won't budge. It says in the service manual that you should push the piston in so that you have enough clearance for the new pads.

Because it wasn't budging, I started looking at the parking brake assembly. I bought this bike used about 2 weeks ago, and the parking brake did not work from the beginning.

I couldn't move the parking brake lever, so I loosed the locking nut, and started to back out the adjusting bolt. Where the adjusting bolt meets the caliper, it's all corroded. So I used a little muscle, and noticed that the bolt started to bend. If I were a gambling man, I'd say it's about to snap.

That's where I stopped. How big of a problem is this? Does anyone have any ideas what the problem could be? Assuming I take it to the shop, what should the repair bill be?

 

Apparently malfunctioning, gummed up, or otherwise useless parking brakes are a common problem. I had a similar situation. The parking brake stopped working at some point, so the previous owner just unscrewed the lever. When I replaced my pads I had to use a c-clamp to push the caliper piston back in. Just make sure you offset the c-clamp so that it is not pressing on the back of the parking brake, otherwise you will be pushing against yourself and won't be able to get the piston to move.

Because parking brakes are so problematic, many people just remove them and install an inexpensive block-off to seal the back of the caliper.

Do you use the parking brake much?

 

I've never used it because it hasn't worked since I bought the bike. (this is my first ATV). Ideally, I would like to be able to use it.

I tried the c-clamp, but couldn't get it to move.

I'm guessing the piston moves a little, because even though the old brake pads were worn, the brakes would stop the bike.

I'm really concerned about the adjusting screw seized up.

 

Have you tried removing the whole parking brake assembly, then see if the piston will move? There should be two bolts that hold it onto the back of the caliper. Removing the parking brake housing may free things up and allow you to see where things may have seized up.