Is it binding? Put on centre stand, raise front wheel off floor, rotate with hand pressure. The pads will drag, but there shouldn't be any serious resistance. If there is, you need to strip the caliper for a rebuild.
Typically on these calipers, corrosion builds up behind the seals, forcing them out, and they bind the pistons. You can see the rubber seal trying to break out past the piston if that's happened to a bad enough degree. When that happens, you get your squeak, because the brake never really lets go. By stripping and cleaning, you can allow the brake to move freely once more. Happily the CB's caliper isn't at all complicated.
Pump the pistons out with the brake lever. One will pop out easier (always does), get the easier one close to the edge first, then clamp that (G clamp is ideal on floating calipers) and pump the stiffer one out. Do Not Pump Them Right Out, or you'll be bleeding the brakes whether you want to or not.
Once it's apart, polish the pistons, you really want them 100% clean. Don't use a steel brush or you will damage the coating and then they're as good as scrap. Best thing to use is brake cleaner but it's quite expensive, so elbow grease and brake fluid will also work.
Hopefullly that will fix it. Otherwise it's time to strip your caliper completely... Repeat above but ignoring That Bit.
Pull the seals out. Depending on what condition they are in, you can usually reuse the oil seals if not the dust seals. Your budget will decide for you, but remember brakes are a serious safety feature of a modern motorcycle - and even a CB-1! It's best to use new ones, as a rule.
www.davidsilverspares.co.uk will sort you out. Don't try and use pattern seals, they are invariably lower quality and not much cheaper. Once the seals are out, use a metal brush (you can get toothbrush sized ones in wilkinsons for £1.50 which are perfect) to scrape any corrosion out of the seal grooves, and line with red grease before putting the new seals in. If the pistons have any serious corrosion, the new seals won't last long. Wemoto will sell you stainless pistons, but I have had a stainless rear piston for a CB-1 and the seals didn't fit to it, the dust seal was too big and bound from new. Therefore, I would still buy OE seals to go with a stainless aftermarket piston!
It's not half as daunting as it sounds!
Please note, you shouldn't use any normal grease on brakes. You should use red rubber grease only on the sliding pins, and no grease on brake pistons, unless you have them right apart, then you can put red grease in the seal groove to help reduce corrosion behind the seals. If you use normal grease on the sliding pins, over time the rubbers will swell, and then the pins can bind, or the boots can split, then you get corrosion build up.
Careful when putting pistons back in, it can be tricky to get them to go in square, and easy to put them in pissed so they get marked.
Post pictures of your caliper if you can, we'll tell you if it's broken.
